The Story of Stuff The Sky at Night

Good evening. For this programme,

we are going to talk about the material that makes up the universe.

But before that, can you remember our Moore Winter Marathon?

We asked you to look at and describe the most interesting object

you can see in the night sky? Now, to find out

what we can see this month, Pete and Paul.

Peter and I have come to Wirksworth in Derbyshire

in the Peak District, to see this lovely work of art

called a star disc.

It has all the constellations which make up the sky

and its creator is Aidan Shingler.

So, Aidan, what inspired the star disc?

I've always been enchanted by the mystery and magic

of the stars, and my interest in the stars

lies in our emotional response to them,

in particular, the power they possess to ignite

our imagination and sense of wonder.

Yeah, it is true. If you look at all the constellations,

they are all the dreams of the human civilisation are put up there.

It's a perfect location to talk about our Moore Winter Marathon.

Fifty objects for you to see in the winter night sky

and many of you have already started.

Here are some images which you've posted on our Flickr site.

Mick Hyde's Kemble's Cascade is at Number 17. It's lovely.

So too is Number 8, the star cluster in Auriga,

taken by Paul Hutchinson.

This wide shot has lots of objects,

Number 7, 8, 9 and 10 on our list.

You just need your Mark One Eyeball for many of the objects.

To help you find them, try using a planisphere.

So, this month we're going to look at some

of the naked eye objects you can see with the Moore Winter Marathon

and I've brought a fantastically simple tool with me

to help me locate these objects.

A planisphere, I've got one of these. These are good

if you're learning your way around the sky.

It's basically the star disc, with a piece of plastic on top

showing the night sky that's available.

That's right, all the stars... shouldn't pull it apart like this...

all the stars you can see underneath represent

all the stars you can see in the sky

-throughout the entire year.

-Yeah.

Of course you can't see that in one go, so what happens

is that there is an overlay printed on the top with a window in it.

That window represents just the stars you can see at a specific date

and time of the year. So what we have to do is put that window

-in the correct position for your current date and time.

-Right.

So, for example, if we wanted to observe the sky

at 10pm in the middle of November,

let's rotate that round so that the time,

-which is 10pm, which is there...

-OK.

...lines up with the middle of November.

Now those stars in that window that we can see represent the stars

we can see in the sky at 10pm.

We also have some other interesting things,

we have the western horizon, the eastern horizon, north and south.

-Those are useful for orientating the thing.

-Absolutely.

Let's start with the south, we've got the southern horizon here,

if you hold it up so that the southern bit is at the bottom,

then that part of the sky

you can see would be what you'd see to the south.

But they are incredibly simple and they don't cost very much...

-No, they don't.

-... a few pounds and it's a great way of finding out

-what's in your particular night sky at any time of the year.

-I agree.

So, let's go on to the Moore Winter Marathon.

Yes, we are going to start over here, aren't we?

Actually, I'm very near to where we're going to start.

-The Hyades and the Pleiades.

-Those are the first two items

on the Moore Winter Marathon. We've also, at the moment got

-a wandering object down there...

-Oh, we have!

-..which is Jupiter.

-It's not on the star disc, because it moves about...

-That's right.

-..over time.

-That's right, it's a wandering star.

-A wandering star.

I feel really guilty because I'm standing on Orion at the moment

and I shouldn't do that to the mighty hunter! If you can locate Orion,

and most people know what Orion looks like,

the belt stars, these three stars in the centre here,

act as a signpost, because if you follow them up

and to the right, they point to Aldebaran.

That's an indicator of how to get to the V-shaped Hyades cluster.

Which is here, this is the Hyades cluster, isn't it?

That's right. But we can also use the Hyades

to locate another object in the Moore Winter Marathon,

-because they're like an arrow head.

-Oh, yes!

If you use the arrow head and point it this way,

you come to a variable star, which is known as Lambda Tauri.

Sticking with the naked-eye stuff, we should move over to the constellation

of Perseus and Cassiopeia.

-Cassiopeia, a very distinctive constellation.

-A W in the night sky.

-And around about here...

-You go from the centre star of the W

to the next one to its left and then follow the line down

-for the same distance again.

-And here's the double cluster.

Yeah, which we can see has a sort of misty patch

with your eyes, but really the best view

-is with a pair of binoculars.

-It is.

-It's quite stunning.

It's that wonderful tornado of stars spilling out into space,

-it's quite wonderful.

-Nice description.

-You like that?

It's mine!

Let's go back now to an object, well it's not an object at all,

-it's a pattern.

-It's your made-up pattern, your asterism.

-It's an unofficial pattern.

-OK, I'll show it out,

I'll walk it out on the star disc.

This is the celestial G and this is what's known as an asterism,

an unofficial pattern of stars in the night sky.

To start out you're going to have to go to Aldebaran.

-Right, OK.

-You've got a bit of a walk ahead of you.

-OK, off we go.

-So head up to Capella, which is in Auriga.

-OK, here we go.

-The yellow star.

-OK, now down to Castor and Pollux,

-the two bright stars in Gemini, the twins.

-There we go.

OK, now down to Procyon the brightest star in Canis Minor, the little dog

down to Sirius, the brightest star in the night sky,

and then Rigel, up to Bellatrix,

and then across to Betelgeuse.

-It's most of the sky.

-It IS most of the sky,

but it's a really fun pattern in the sky,

especially for kids to point out

-some of the brightest stars that you can see.

-It is.

Let's hope we get some cold, clear nights in November

for you to take part in our Moore Winter Marathon.

You can find the lists, guides and information on our website.

Next month we will talk about

some of the things you can see with a pair of binoculars,

a whole world of clusters and even a galaxy.

Now, over to Chris Lintott, on Selsey beach,

on the trail of dark matter.

It's the story of stuff and what makes up our universe.

Everything's the same here on Earth

whether it's the sea, the air, the rocks,

they're all made of atoms, whether it's hydrogen,

oxygen, nitrogen or any of the rest, it's all the same.

But that's not true of the universe.

Wherever we look in the universe, rather frustratingly,

something just doesn't quite add up.

In the cosmic sweet jar,

the coloured jellybeans represent the stuff that makes up you and me,

which makes up the planets, the stars and even the galaxies.

The rest, amounting to six times as much, is made of something

we don't see, a mysterious substance known as dark matter.

In our cosmic sweet jar, the result is more black jellybeans

than anyone could possibly devour,

but in space, the consequences are rather more serious.

Dark matter is responsible for shaping everything that we see.

What's so shocking is that there's so much dark matter

and yet it eludes direct detection.

We can see its effects, we just can't hold it up for inspection.

So, Carlos, I think we've got some jellybeans

to help us illustrate dark matter.

Both Carlos Frenk and Chris North are joining me

in the search for dark matter.

We must make sure, though, that people realise

that the dark matter is NOT made of jellybeans.

Well, even with jellybeans,

it seems like a strange idea

that we don't know what most of the universe is made of.

-But it's not a new idea, is it?

-It's not a new idea

but it's certainly the case that dark matter

is one of the most profound mysteries in science today.

The story goes back to the 1930s,

when astronomers realised that galaxies

are not just uniformly distributed around the cosmos,

but they like to collect in entities that are well defined.

The most visible of those are galaxy clusters.

Big cities of galaxies, hundreds of galaxies.

Hundreds or thousands of bright galaxies,

all making a galaxy cluster.

So, what does a cluster tell you about dark matter?

It was recognised that galaxies in the clusters are swarming around

and astronomers asked a very simple question -

what keeps a galaxy cluster together?

What is confining the galaxies in the cluster?

It must be the force of gravity, what else?

Then came the real shock, because when astronomers worked out

how much gravity the galaxies that we could see produced,

they realised there was a gravity deficit.

They realised that there had to be 10 times more mass in the cluster

than the mass they could see in the form of stars.

Essentially, we can weigh the stuff we can see, we can weigh the stars

and the gas and the dust in these galaxies.

by essentially counting stars.

We understand stars, stars are nice and simple...

But they're not enough. They were not enough.

It was recognised that something else that's not stars, it's not gas,

it is something else - hopefully not jellybeans!

Something else was responsible for keeping galaxy clusters together.

And this news came as a shock. It was a real stunner.

The universe is full of stuff we cannot see.

So, that was the 1930s and this endured as a mystery

and then I guess the next shock came when people looked,

not at clusters of galaxies, but at galaxies themselves,

individual galaxies like our own Milky Way.

Exactly. And the story was exactly the same.

In a galaxy, a beautiful galaxy,

these amazing things that nature has made,

these galaxies with stars, going round and round

the centre in circular motion.

-Just like the sun goes round the centre of the Milky Way.

-Exactly.

-Why does the Milky Way not just fly apart?

-The answer is gravity again.

Not the gravity we can see because that's only a very small fraction

of the gravity that's needed,

so we now know that galaxies like our own Milky Way

are sitting in a clump

of something we cannot see, a clump of dark matter

and it is that dark matter that keeps our galaxy in place.

Thank God for dark matter, otherwise our galaxy would not exist!

And it's distributed differently,

so if you think of our galaxy, as Patrick would say

as two fried eggs back-to-back, a disc,

and a bulge at the centre, where's the dark matter?

The dark matter is very much not in the disc,

it's in a much larger volume, it's in what we call a halo.

It's a spherical region, roughly, around the galaxy,

so if we look at other galaxies, we see the discs of stars

and gas and dust and all the normal matter, the ordinary matter.

And if we then say where the dark matter is,

it's in this roughly spherical blob, this halo

around them and quite a lot larger than stars are as well,

it's normally a few times bigger and you get this halo...

It's the gravity from the halo that keeps the discs stable

-and enables it to be able to turn.

-Most of the exciting stuff, really,

-is the dark matter.

-You're a fan of the black jelly beans in other words.

I like the black jelly beans. The coloured ones, I never know which colour to choose.

I don't really know what's inside them.

Dark matter is almost certainly some elementary particle,

some mysterious and yet to be discovered elementary particle

Some physicists believe that they narrow down the possibilities

and that, in fact, we are zooming into the identity

of the dark matter. Whatever it is,

we know it's everywhere, it's not just in galaxies, it's everywhere.

-It permeates...

-It's passing through this room right now?

It's passing through the room and as we speak,

there are billions of particles of dark matter going through

your body, you just don't feel them

because they produce gravity but gravity's a very weak force.

They don't interact with the rest of me or my normal matter, they just pass through?

They pass straight through, they leave no sign,

they're not radioactive, they do not collide with any of your atoms

-and that's good for health and safety reasons.

-Yes, good.

It's bad if you're an experimental physicist

and you want to detect them.

-You want to catch them as they go past.

-You can't - they go through your instrument.

The only way we measure dark matter is through its gravitational pull,

-for its effect on other particles.

-For the most part.

The problem is that gravity... the mass is really hard to measure,

that's why it's so hard to pin down.

We can work out it's roughly in these spherical blobs,

these halos around galaxies,

but working out exactly what shape they are

is actually really very tricky.

-Surely you're really fishing in the dark?

-Yeah.

We need more evidence to support such a strange theory,

so what else have you got?

Well, I agree. Extraordinary claims

require extraordinary evidence

and the other source of evidence for the existence of dark matter

comes from the phenomenon of gravitational lensing.

-So, this is Einstein's old idea?

-Einstein's old idea.

Let me explain to you how gravitational lensing works.

In everyday life, light travels in a straight line.

Not so when light wanders near a concentration of mass.

A large concentration of mass.

A very large concentration of mass, light can be bent by mass.

Now, imagine Chris is a background galaxy.

OK. You're doing a very good job.

He looks like one. He looks galactic.

Here is a galaxy cluster...

With some dark matter and some ordinary matter.

And some ordinary matter. And Chris is a source of light,

the light ray from Chris coming towards me -

I'm the observer - will be bent by the concentration of mass.

Bending of the light will cause Chris to become blurred

and distorted.

In a characteristic way, right?

-In a characteristic way.

-What he means...

-We will see you

as an arc and if you look at galaxy clusters,

you see these arcs, don't you, around the outside of the cluster?

And if you get it exactly lined up, you get a full ring,

it's called an Einstein ring.

Now, how does this tell us about dark matter?

-Well, I was about to ask.

-Well, you can look at a galaxy cluster

and the way it bends light and you soon conclude,

if you can do your sums correctly,

that the amount of mass in the divisible part of the galaxy

-is nowhere near enough.

-We are using this as a way of weighing

this cluster that's in the way, essentially.

The answer is it weighs about ten times more than the mass

that you can see directly in the form of stars. Ten times more.

The number we got from looking at the movement of the galaxies.

Two very different ways of weighing the cluster and they tie together.

And they give us the same answer.

How can we get a better understanding of how much dark matter there is?

Astronomically, the evidence gives us an approximate number,

but indeed the universe has a way to tell us

exactly what it is made of.

That takes us back to the very beginning

of our universe. Almost to the Big Bang itself.

We now know that when the universe was a mere 350,000 years old,

the fog of the Big Bang lifted

and the glow of the Big Bang explosion

was able to propagate freely until we detect it.

And we see this as the cosmic microwave background. You studied this.

As we look further out into space,

because light travels at a particular speed, we see things

as they were further ago. We see the sun

as it was eight minutes ago and so on and so forth.

If we look really far away, we look billions of years back in time

and so we see the universe as it was when it was very young

and we see it in microwaves, it's actually all very similar -

the early universe was very uniform -

but there are bits that are more dense and bits that are less dense

and we can map out the temperature of the early universe

and the density of the early universe.

The first map of these hot and cold spots

really changed our perception of the universe,

because here we were, looking at the baby universe

and this baby universe reveals the secrets of the cosmos

and in particular, the pattern of hot and cold spots

allows us to infer, using the laws of physics,

the exact composition of the universe,

the exact mixture of ordinary material and dark matter.

And that, through measurements of these, that is what tells us

with great precision that 84.5%

of the matter in the universe is dark

and the remaining 14.5% is, in fact, ordinary matter.

Approximately, one part of visible for six parts of dark.

And it is this precision with which we can measure this

that allows us now to go on to the next important question -

what is the dark matter?

One way to solve that mystery is to try and make some dark matter.

We can see the effects of dark matter in space,

but for the last quarter of a century,

astronomers have been trying to find it here on Earth.

They bury their detectors deep underground and just a few years ago,

The Sky At Night descended into Boulby salt mine

in Yorkshire to see what a dark matter detector would look like.

Here I am, in a lift going three-quarters of a mile underground

in Boulby mine towards this strange observer thing.

Despite all this effort, dark matter is still elusive, and so, instead

of waiting for a direct hit down in a mine,

some scientists have grown impatient and they're trying to produce

their own dark matter at the world's was famous laboratory, CERN.

We think of objects like this rock as being pretty solid,

but it is not, it's full of billions of separate atoms,

each one has a nucleus, with protons and neutrons,

surrounded by a cloud of electrons.

Inside each proton is a whole world of even smaller particles,

whose effects become apparent when protons are smashed together.

In Geneva is the world's largest machine,

the Large Hadron Collider, or LHC.

It's probably the most sophisticated experiment ever carried out

and it's certainly impressive. Here, protons are accelerated

to close to the speed of light

and then smashed together so that physicists can pick over the debris.

It's weird that the very small stuff that we look at

actually influences the very big-scale stuff in the universe.

Astronomy and particle physics together.

John Butterworth was part of the team that used the LHC

to find the infamous Higgs-boson particle,

the one that gives everything mass.

In looking for the Higgs, they had to recreate the conditions

that existed in the early universe, just after the Big Bang.

-How's the early universe different from today?

-It's about symmetries

and the best way to explain it is with a wine bottle.

Good. I like wine bottles, so that's excellent.

I look down the bottom, it's symmetric, all round the middle.

So any direction's the same at the end of the bottle.

That's right. Put something in it.

I've got one of Carlos's jellybeans, luckily,

-so let's drop that in.

-That'll do.

-If you look down, it's not symmetric.

-The bean's at the bottom.

-The bean has broken the symmetry. Yeah?

-Yeah, that makes sense.

-That's no longer symmetric.

-The early universe was very symmetric.

The reason was a lot of energy, so the bean was jigging round.

There's an equal chance it'll be anywhere around the sides of the bottle

-It might be on the left...

-It's symmetric round the middle.

-We're back to a symmetric universe.

-That's right.

But as you cool down past where the energies of the LHC are...

The universe expands, as everything cools down,

if you don't have a collider, the bean drops to the bottom.

This is everyday life, the bean is off on one side, the symmetry's broken.

It's only by having the symmetry, the symmetry's still in the bottle,

-we haven't changed...

-We haven't changed the universe or physics.

It's the cold bit when the bean's no longer got loads of energy,

then the symmetry's broken. And that symmetry breaking there

is actually how mass occurs in the universe,

the only way we can have the symmetry we need in the theory

at high energies or have mass in everyday life, which is clearly there...

-Yes.

-..is to have, basically, a bean in a wine bottle.

The symmetry that's broken, that's broken by the thing slowing down,

but is there again if you give it lots of energy.

And that idea of symmetry is so fundamental to physics.

-And there we are with a wine bottle and a bean. Fabulous.

-That's right.

Whenever the particles collide,

all the debris should fly off in a roughly symmetrical fashion.

If that doesn't happen,

then that might be the signature of dark matter.

The sign we're looking for might be there already,

buried in the data that the LHC has already provided.

Now, you found your Higgs so particle physicists are happy,

though you've other stuff to look for. For us, as astronomers,

what we need you to do is to find dark matter.

Is there any hope of the LHC helping us out?

There is indeed hope. You may be surprised to hear that, actually,

because dark matter is, of course, dark and hard to see.

But there is a chance that the LHC is actually a dark matter factory,

-that were actually making dark matter in there.

-Right now?

-Yes.

It will be hard to see, in fact, the particles themselves, we will not see,

but we surround the beam with these huge detectors

which are essentially concentric layers of different technologies

to interrogate these collisions. So, if we see something

flying off in one direction and nothing in the other direction,

then we know something's missing, we know the event's imbalanced,

-and something must have been there.

-The rules of physics say,

-roughly, things have to go in equal directions.

-The momentum is conserved.

That would look like in your detector if you've got your collision here,

you'd have stuff going in this direction, and if you see nothing,

-you know you were missing something.

-Exactly.

-Any sign of dark matter yet?

-No.

And that's expected, right? It's going to take a while.

There are a lot of theorists who thought we might have found it by now

and would have told us experimentalists we would have done, but we haven't yet.

The thing is... the whole business of the galaxy

is that we're looking at this completely new regime of physics,

where these forces unify, where the Higgs lives...

-As you said, that's the point.

-That's right.

There's a very good chance that if dark matter

is a new fundamental particle, this is the region where it lives.

There's still plenty of space to look. We started looking

and we've kind of landed on a shore of a new country of physics,

OK, the dark matter wasn't hanging around on the beach,

but it might be further inland, we're exploring that now

and we've got a lot of exploring to do.

To understand dark matter,

we have to go almost all the way back to the Big Bang.

In that maelstrom of rapidly moving and colliding particles,

the very building blocks of matter itself were being formed.

In the early universe, we don't just have ordinary matter,

we have antimatter, particles of the same mass

but with a different charge. Look, this sand castle

has about a billion sand grains in it,

but in the early universe we'd also have

a billion particles of antimatter.

Now, when matter and antimatter collide, they annihilate,

producing light, so if we mix these two together,

we lose everything, we get a universe just filled with radiation.

The only thing that saves us is that as it turns out,

for every billion antimatter particles,

1,000,000,001 matter particles existed

and it's from these leftover particles that you, me, the Earth,

the sun, even the dark matter forms.

Why this should be, we have absolutely no idea.

But one day, the LHC just might be able to answer

this fundamental mystery, too.

We're still only in the very early stages of its voyage of exploration,

but nature doesn't give up its dark secrets easily or quickly.

In the meantime, astronomers can still see the evidence

for dark matter. The most powerful telescopes in the world

stared at this collection of galaxies

and by watching how light is bent as it passes,

we can build this computer simulation of the dark matter,

showing the galaxies embedded in a wider cosmic web.

We don't have computer simulations, but we do still have our jellybeans.

Dark matter's great fun, this great mystery, this unknown of the universe,

but why does it matter, why do we care about dark matter, Carlos?

Why does dark matter matter? Well, it matters a lot.

In a sentence, without dark matter,

we would not be here.

Nothing of what we know in the universe would exist

without dark matter.

Dark matter is the architect of the universe,

it's the agent that has enabled the universe

to create all these amazing galaxies and stars that we see around us.

Without dark matter, the universe would be completely boring,

it would be totally uniform and there would be nothing.

-Let me show you this.

-Yeah, sure.

We start off with a very smooth universe.

The universe was very smooth. It was very tiny.

There were more irregularities.

-Here's how you smooth the universe.

-OK, full of dark matter.

-Nothing, full of dark matter. In the proportion of 1 to 6.

-OK.

All mixed up and all without any structure, without any shape,

without anything interesting.

Then, inexorably, gravity begins to work

and the way it does it,

it exploits small irregularities in this initial...

So, the places that just happened to have more stuff...

-..accumulate more.

-They pull more in, the rich get richer,

the poor get poorer. A fundamental rule of the universe.

Low-density regions become void,

the high-density regions become clusters

and the voids and the clusters

produce intricate patterns

that we refer to as the cosmic web.

So, one of those blobs in the microwave background

is representing a pattern of the universe

that was slightly denser than the ones around it.

-They had more stuff.

-Slightly more stuff in it,

and because it had more stuff, more gravitational attraction,

it pulled more stuff in, it got denser still

and that gradually accumulated stuff and gravity did its work

to give us the universe we see today.

Yes, the dark matter particles accumulate

and the ordinary matter just follows.

We've talked almost entirely about looking up at the skies

to see dark matter, we've talked about...

trying to make our own dark matter, but we can also try and detect

the billions of dark matter particles that are passing through us.

There's a group in Italy who tell you they've seen the effect of dark matter.

Yes, I think this is like the 100m race in the Olympics,

that you get, as the tension builds up, you get false starts.

We've had a few false starts.

I don't think these claims are yet conclusive,

they are disputed by many other groups

who've failed to find the signals,

but it tells us, this turmoil in the community

and that to me smells like something very close.

So, I personally, I have a feeling

that we're really homing in and if we don't find it,

then I think things will get very interesting.

Because if we don't find it, then we can't explain this universe.

Exactly. Or it tells us dark matter is not what we think it is.

So, if we don't find it within a reasonable amount of time -

I won't tell you exactly how many years -

then we will have to conclude that these...

we're going up the wrong path.

And we have to turn, make a turn,

-and look for a different kind of particle.

-We'll see what happens,

but I think it's amazing that we've come so far

and yet there's so much of the universe that we don't understand.

I think we should consume this universe. What flavour do you want?

-I'll go for some red matter.

-I'm eating the dark matter.

Yeah, me too, I think it's really what's most important.

It's made of strawberries.

Now, on our next programme,

we're going to talk about Mercury and the moon.

So, until then, good night.

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