Why Mountains Are So Small Royal Institution Christmas Lectures

CHEERING AND APPLAUSE

Thank you very much.

My name is Mark Miodownik, I'm a material scientist from King's College, London.

Today we're going to talk about big stuff! Look at this stuff.

Look at this bolt.

Who could need a bolt that big?

And this stuff here. We're going to talk about skyscrapers,

mountains and planets, huge things.

We're going to see that matter behaves on the big scale

every bit as strangely as it does on the micro, tiny scale.

In the previous lectures, we talked really about how different forces dominate at different scales.

At the big scale, the force that we're going to need to worry about,

the one that's going to dominate everything, is gravity.

It's our invisible enemy.

So how do we beat it?

How do we make big things?

This is a big thing. This is a mountain.

It's huge. Look at it.

Absolutely huge. Or is it?

It all depends on the size and scale at which you look at it.

If I zoom out now, now I'm the size of a planet, and I look down, well, mountains aren't so big any more.

When things are big,

it changes everything.

You suddenly realise that

all the rules are off.

Matter behaves in a totally different way.

I want to get you used to that idea.

I'm going to need you to turn off your common sense in order to understand that kind of thing.

Your common sense is really going to interfere.

So first of all, let's get a feel for how gravity can affect big things.

So I've got a material here, and it's a liquid.

Who believes me that this is a liquid?

OK, so you've still got your common sense turned on.

I'll try and turn it off for you. Obviously, liquids don't do this...

usually, do they? This feels very much like a solid.

But I hope to prove to you, as the lecture goes on, that this is a liquid.

I'm just going to leave it there for the moment. You keep an eye on this stuff.

We'll come back to that.

Here is another bonkers, mad liquid.

This is one of my favourite liquids of all time - mercury.

Gosh, who loves mercury? It's just the strangest stuff, isn't it?

This... What's so strange about mercury is it's a metal but it's also a liquid at room temperature.

Mercury is a heavy liquid. What does that mean, heavy?

Well, I'll illustrate what I mean by heavy. This is a cannonball.

That's definitely heavy.

Gravity, this invisible force, pulled it down.

Did you see that? You're probably used to that, aren't you? OK, let's see.

Heavy cannonball, meet heavy liquid.

We'll take that off. What's going to happen here, eh?

Is it going to go right to the bottom?

Wow! That's incredible, isn't it?

A floating cannonball.

Let's hear it for the cannonball!

APPLAUSE

All right, so that's heavy things, things where gravity is really playing a massive force.

Now I'm going to show you a material that goes completely the opposite direction.

I have here the lightest solid in the world.

It's so light, you can't hardly see it.

Can you see that? This stuff is called aerogel, and it's 99.8% air.

It's only 0.2% solid.

In fact, you can hardly see where it ends and the air begins because there's only 0.2 difference.

It's got this blue tinge, have you noticed that?

That's because it's a foam. It's a glass foam.

The holes in that glass foam are so small that they

scatter light, in the same way that light is scattered in the sky.

So you're seeing it's blue, for the same reason that the sky is blue.

There's no pigment in there.

So this is as close as you'll ever get to holding a piece of sky in your hand.

It's almost completely sky.

You think, "That's incredible, 99% air.

"What could anybody possibly want with a material like that?"

It turns out that NASA use this to collect space dust.

Absolutely amazing, isn't it?

So, I think you have to give a big round of applause for aerogel, the lightest solid in the world.

How are we doing with our common sense?

It's looking less like a solid now, isn't it?

Let's see how big we can build.

This is the Burj Khalifa, the tallest building in the world.

It's 0.8 kilometres high, so that's half a mile high.

Of course, I look quite big next to it, don't I?

I look like a giant.

But actually, if you shrunk me down, this is what I'd look like.

It's really high!

It's absolutely a magnificent building.

But, well, what happens if I'm the size of Everest?

Now, here I am, I'm a giant.

If I was to look at the Burj Khalifa now, that's how high it would be.

It's down here, tiny.

So why can't we build anything bigger?

That seems pathetic.

We've gone to the moon, and yet that's all we're building.

We've got a model here of the Earth.

Here's England. Here's where we are.

If we were to put on a scale the Burj Khalifa, you wouldn't be able to see it.

We'd need a microscope. It's down there but we haven't seen it.

If you were to put the mountains on here, again, as you saw with the pictures of the Earth, they're tiny.

So this Earth, you can see, has this incredible roundness, it's all very, very smooth.

That's because the Earth exerts an enormous gravitational field. It's huge.

This enormous mass is exerting a force on you, me, that cannonball.

How far do we have to go to get out of its hold?

I'll show you.

I'm going to just say, if we were to build a building this high...

Not quite this high, a bit higher.

And a bit higher, and a bit higher,

and a bit higher, and a bit higher, and a bit higher, and a bit higher, and a bit higher,

and a bit higher!

If we were to build a building, and this is the scale,

if we built a building 36,000 kilometres high,

we'd be at what's called a geostationary orbit.

So satellites, communication satellites up there,

they stay in a fixed position with regard to the

Earth as they satellite around, and they aren't sucked back into Earth.

So if we can get up there, 36,000 kilometres away from the Earth,

then we can escape the Earth's gravitational field, this tyranny of gravity.

So why haven't we done that?

Why haven't we managed to do anything close to that yet?

I'm going to need a few volunteers from the audience to help me.

One there. A lady there.

Let's get a guy, yeah, go on.

And one more. Yes. Why don't you come down?

APPLAUSE

We're going to have a competition now, and there will be prizes.

The competition is to escape the Earth's gravity.

LAUGHTER

So, what I'm going to try and do is, obviously you're going to try and jettison off into space.

If you make it as far as the roof, we'll open it for you.

So don't worry about that. Don't limit your ambitions. Are you ready?

OK, we'll do a countdown, everybody. Three, two, one. Go!

Oh... Oh, you did it twice! We'll have to consult the referee.

They're letting that go.

All right. But let's have a look at the action replay. Up they go.

It was the old back flips, I think that got it for you.

Well done. Technique!

APPLAUSE

OK, that was really sporting of them, but it wasn't very impressive, was it?

Half a second is all we could...

And they're no better or worse than most of us. So gravity is this incredible tyranny on our lives.

It's constantly gluing us to the floor.

That seems really annoying to me. So I started thinking, let's try and work out how to levitate.

So here we go. I thought,

"We should be able to make a levitation machine."

Got in touch with some material scientists who had some ideas about this, and they gave us

some of this material, which is called a superconductor.

When you cool superconductors down with liquid nitrogen -

so we're going to get down to minus 193 degrees centigrade -

then these superconductors, they repel magnetic fields.

So the idea is this. Gravity pulls magnet down, and we repel magnetic

field with the superconductor, and they equal each other, and we get the magnet to levitate.

All right, let's see if it works, though. Is it working?

Oh-ho-ho-ho!

APPLAUSE

I know what you're all thinking.

You're thinking there's a tiny little thread, aren't you? I know.

So, look, just to prove to you that there's isn't anything underneath or over the top...

Nothing over the top. And...

AUDIENCE GASPS

-APPLAUSE

-Oh, yes.

The thing about that was you had a magnetic field opposing the gravitational field exactly.

Turns out that, as the magnet gets bigger and bigger and bigger, that gets harder and harder to do.

So I thought, "I'll invent a levitation device that can levitate me".

So off I went to my garden shed, and I came up with a levitation device,

and this is the world premiere of this device. I think you're all going to be very impressed.

This really could be the future of us getting off this planet.

-Do you want to see it?

-ALL: Yes.

You don't sound that interested.

-Come on, do you want to see it?

-ALL: Yes!

-OK.

-DRUM ROLL

You're clapping but I know you're not that impressed.

But just bear with me on this one.

This is a levitation device. I'm on the floor, I'm stuck to the floor.

Now I'm not. Right?

Before, we had a magnetic field repelling my gravitational force.

But now, inside this piece of wood, as we call it in the technical...

There's an elastic force field which is exactly matching my gravitational field.

So there's an elastic force field in there.

At the atomic scale, the atoms are being pulled apart exactly to match

by gravitational force. So this is fantastic.

And it's not just happening to me, it's happening to all of you now.

All of you are sitting down and gravity is still acting on you.

Gravity isn't this force that just acts, switches on when you're falling. It's acting on you now.

It's pushing you down to the ground, and if there wasn't an elastic

force field underneath your bum now - let's all just think about our bums - no, not too much!

That's enough! So it's that elastic force field underneath

your bum, so it's the cushion and it's the floor, isn't it?

If you think about it, the floor in here, in this whole auditorium, is having to put up with quite a lot.

Before you lot came in here, there wasn't an elastic force field, and

now there's a massive elastic force field in here holding you all up.

So that's great, isn't it? Buildings just do that for free. Or do they?

Let's get a feeling for how much elastic force field they're having to put up with now, in this room.

OK, so how do I do that? Anyone got any ideas how to calculate the total gravitational force acting down now?

Anyone? You've got an idea.

-A force meter?

-A force meter, yes.

-And what do we call force meters, in the parlance, in the bathroom perhaps? Anyone? Yes?

-Scales.

Scales! You, you're good.

So it's a scale.

If we're going to measure this audience, we need a scale that will weigh you all, don't we?

So let's get in a big scale. What we thought we could do is get you all to sit on this scale.

We borrowed these from Shrek.

He has them in his bathroom and he let us...

He's on a diet at the moment.

He's obsessed with his weight. What we want to do is try and measure

the audience, how much gravitational force from the audience.

So I need some help with this.

I'm going to try and weigh as many of you as I can.

But first of all I'm going to start with one. Can I get someone in the front row who's brave enough?

Are you brave enough to come...?

How do you feel about your weight? Are you sensitive about it?

-LAUGHTER

-No, you're not. What's your name?

-Tomasz.

-Tomasz?

-Yes.

-OK, brilliant.

So, Tomasz, I'm just going to zero the scales. Off you go.

Let's see, how much do you weigh?

41 kilos. Is that about right? Good.

Now let's see if we can get some more on.

Can we get two more of you on there?

Is that possible? Are you two up for that?

All right, come on, then.

You two get on there, and budge up a bit if you don't mind.

How are we doing? 128 kilos.

Do you think you three will be able to get on there? All right.

How are we doing? 309 kilos.

What about you two? Are you going to make it on there?

You can get on the edge bits, as well. What about you guys?

Are you up for it? So, you four.

Let's see if we can get four more of you on.

There's a game called sardines that's very similar to this!

This is good. We're up to 600 kilos.

Can we get any more?

Come on, let's get the whole of this row on if we can. Is that possible?

How are you guys feeling? Are you all right? Is there room?

-No!

-Come on!

There's a bit of space over here.

You came up with this idea, so you should be at the front. Brilliant.

And can you get into that little corner there?

You'll all get to know each other. This is all very friendly. Oh, no!

Is there not enough room for you guys at the back?

Is there a little bit of room there? OK, hold on, guys, just two seconds.

So we've got 700... Are we on?

771, no, let's say 775 kilos.

For how many kids? Oh, I didn't count.

-LAUGHTER

-Did anyone count?

All right, let's get off, guys. Thank you. A big round of applause.

1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16.

16 kids, I think.

So that turns out to be, has anybody done that calculation in their head?

Average weight of kid?

48 kilos per kid. So let's say 50. And there are about 400 of you here.

So that means...

A bit of mental calculation going on in my head now... 20 tonnes.

So you weigh 20 tonnes.

That's pretty amazing, isn't it?

So before you came in here, this poor building was minding its own business,

just having a lovely Saturday afternoon, having a bit of a rest,

then it had to put up with 20 tonnes of you, and it's holding you up like this, and we never really asked it.

So it's produced an elastic force field of 20 tonnes just like that.

Next time you go out and buy a really heavy, big, new, flat-screen TV, think about the building.

The poor old building never got asked if he wanted a big flat-screen TV that weighs half a tonne.

And it has to put up with holding it even when you're asleep.

Those of us in the Society For Protection To Cruelty To Buildings

are quite concerned about this accruement of very heavy technology in the home.

OK, so it turns out that buildings are quite good at coping with this.

So why can't we just build ourselves off the planet?

I'm going to need a couple of volunteers who kind of, who have ambitions to work in engineering.

The hands are still up. Fantastic, I love that!

Let's have you, Sir, there.

Yes, brilliant. And, Madam.

-APPLAUSE

-All right, what's your name?

-Charlotte.

-Charlotte. And your name?

-Dennis?

-Innes.

Innes. Innes and Charlotte, OK.

In this game, you do all the work and I get to talk.

Is that all right? Anyway, we're going to try

and build ourselves off the planet, well, at least the first few steps.

And here they are. So we've got the first step.

This is my anti-gravity machine, which we now agree is genius.

If you could just add, can you grab some of those and add the next step?

That's what we want to do.

I want to basically get the idea of building us off the planet, so you put two on there, fantastic.

I think if we can get a slat across, yes, that would be brilliant.

I'll put that on. I do the easy bit.

Hooray, I'm up. One further bit away from the planet.

It's like an enormous game of Jenga, although I hope it won't end the same way.

Look, guys, you've done a fantastic job. Here we go, up I go, and we could just keep going, couldn't we?

If you weren't getting tired and had infinite energy and we had infinite materials. That seems reasonable.

Well, thanks very much for helping me with that, guys.

I really appreciate that.

APPLAUSE

What's stopping us just keeping on going?

Hm. Well, there is a problem.

There is a problem.

In order to tell you about that problem, I'm going to invite some friends to help me work it out.

# F-O-R-C-E Let's learn about gravity

# F-O-R-C-E Let's learn about gravity

# F-O-R-C-E Let's learn about gravity. #

Five, six, seven, eight.

APPLAUSE

Well done, guys. Fantastic.

OK, well done, fantastic.

Now, who was at the top? What's your name?

-Keira.

-Keira, you were at the top.

How was it at the top? Did you feel an enormous force on your shoulders?

No. Did you feel yourself pressing down on other people? Yes, you did.

And how was it at the bottom?

You guys were at the bottom, I was at the bottom.

Do you guys take it in turns? What goes on?

Nah, we've got all the weight.

Basically, this is the problem, isn't it? As you build things

higher and higher, you guys are always going to have to take all the weight that goes above you.

-Yes.

-That just gets worse and worse.

So if we put another tier on top, which we're about to do, aren't we?

-LAUGHTER

-Oh, no, just joking!

We'll just run that through again,

cos we want to get the hang of it, and I want everyone to look at these guys' faces on the bottom.

Not the top - she gets all the glory.

Look at the people doing the work at the bottom.

Let's go for it again, guys.

Five, six, seven, eight.

APPLAUSE

Let's hear it for these guys.

So what we saw there is, if buildings had emotions,

right, all the bricks and stones at the bottom would be going "Arrrgh!"

all the time, wouldn't they? They've got to hold the whole building up.

As the building gets higher and higher and higher, their load doesn't get any better.

They have to take more and more weight, so gravity is

constantly working, even in static structures like this.

What we have to do is find the materials that can cope with that kind of pressure.

Phew!

OK, so remember, we're trying to work out what makes materials strong.

We're going to do a test now.

I need a volunteer to help me work out what are strong materials.

Let's take you over there. Fantastic.

-What's your name?

-Natasha.

-Natasha, OK.

-Are you up to helping me work out which are strong materials that we need for building?

-Yep.

If you go round that corner there, I'll come round here, I'll join you.

What we're going to do is, we've got here a dresser like you might have at home, with some objects on it.

We're going to try and test them to destruction.

To get you in the right mood for this, I want you to think

about the most furious moment in your life and how you felt,

and in that moment you thought, "Gosh, I really want to throw this ball at that", didn't you?

I'm also going to get you to put some safety goggles on.

Is that all right? So you're holding that thought, furious, and of course

you could never do this at home, you'd never do this at home.

-But here you can do it. Is this going to be the happiest moment of your life?

-Yes!

It's going to be a competition, which is always the way with me.

You're going to get three balls, I'm going to hand them to you, and I'm

going to get three balls, and we'll see who can smash the most.

-OK.

-That sound fair? I'm thinking furious thoughts, you're thinking furious thoughts.

-Let's see which materials can survive.

-OK.

Off you go, you go first.

OK, wow. All right, I'm going to do the same.

Not too bad. One each. Off you go.

Wow, you're quite angry inside!

LAUGHTER

All right, last go.

Oops.

I'm actually quite nervous now.

Now, what's the score, everybody?

Did you get this?

It's one each. I think it's a fair fury divide between us.

Thank you very much indeed.

So look, let's just look at the wreckage in here.

So this got hit, but actually, this is paper and survived. It's all right, isn't it?

And this metal plate got a bit dented but survived.

So they seem good candidates for strong materials.

This cup bit the dust, big time.

-Porcelain cup, clearly a weak material. Wouldn't you agree?

-Yes.

Oh, you would, would you? You've fallen into my trap, ha-ha!

All right, is it weak? Let's see.

I've got a replica cup here.

I want to show you how thin this is.

You know how thin they are, but I'm just going to show you.

Porcelain cups are fine bone china. You can actually shine lights through.

Look at that. It's that thin.

We're saying this is weak. But is it?

I'm now going to do something which you shouldn't do at home.

In fact, you shouldn't do any of this at home. Will you promise?

I'm going to stand on this cup and see if it really is so weak. I'm pretty hefty.

I didn't get on the scales earlier cos I was a bit embarrassed.

But you see, I've got a lot of weight, gravity's pulling me down,

all of my weight is going on the cup. No problem at all.

So it seemed quite strong there, didn't it?

I know what you're thinking. You're thinking, "They've got a dummy cup.

"This is a super-strong cup and that was a weak cup."

So just to prove to you that's not the case, and because I can...

So the cup was pretty strong when I stood on it.

But is it going to be able to survive this?

No. Phew!

So what's clear from any tantrum you've ever had, and this test here,

is that there are different kinds of strength of materials.

You've got a strength here which is about impact strength, and some

things are great under impact and they're terrible under other things.

So paper was good under impact, but if I put a paper cup down here, it would crush. On the other hand,

the ceramic cup was terrible under impact and is fantastic under the compressive forces of me.

So when we think about building a building out of materials, what we really need to think about is

which type of strength we want, and in the case of a building, we want more like the compressive strength.

So we have to make sure we're picking materials with high compressive strengths.

What do I mean by ceramics and that kind of thing?

A ceramic is a tiny... We saw it with the porcelain cup, it's tiny little crystals inside there.

They're the same sort of crystals in jewellery.

They're like rubies and sapphires and all these

kind of aluminium oxide, silicon oxide, and they're tiny little crystals all bunched together.

That cup seemed like a really good material to build a building out of.

So you're thinking, "Why don't we have enormous buildings made out of cups?" Well, we do.

Ceramics, that material, that class of material, is the same material as bricks, and it's the same material

as stones and rocks and all these kinds of materials. But I want to show you an even better material.

And this is it. Concrete. Absolutely fantastic material.

This is such an amazing material, and we all just take it for granted, I think because it looks so sort

of grey and dull, and so we think it must be grey and dull if it looks grey and dull. But it isn't.

It's the stuff of absolute fantasmo. Is that a word?

Anyway, I've said it. Look. Inside here is cement and gravel, and if

you set this, you can pour it, you can shift it up 200 metres in the air,

pump it up through huge pumps.

That's how they make really tall buildings.

They pump it up. So it behaves like a liquid, even though it's sort of a gravel aggregate.

Then when it gets there, it'll set.

It's not, as you might think, drying out. Actually, a chemical reaction is happening inside it.

Let me show you. This is what's happening.

Little crystals are growing inside the concrete. This is a ceramic.

It's incredibly good compressive strength.

What happens is that you've got this, basically a liquid rock which you can pump anywhere, you

can pour anywhere, you can bring on, and then you can make these enormous

buildings, and then when they set they have huge compressive strength.

So this is a fantastic material.

In fact, it seems we've kind of come to a material

we need to make big buildings that build us off the planet.

We need rock, basically - ceramic. It can be concrete or it can be stone, but this is the way, surely,

this is the way to build huge buildings.

Well, it's no news. You know it.

We've been doing it for 5,000 years.

Let me show you. It's getting a bit hot here.

Yes, it's good to get some winter sun, don't you think?

Look, I'm by the pyramids in Egypt, and these buildings have been built

out of stone and they really show exactly what I'm talking about.

They have lasted for 5,000 years, there's enormous compressive stresses at the bottom and they've

been there for 5,000 years and this rock has not given up.

Incredible down here.

So, surely this is the right, both material and structure

to start building ourselves off the planet.

So, let's think about this. If I get a map out of central London...

This is to scale.

We are... We are...

That is a very strange material.

Hm! Anyway, sorry. We are...here.

Albemarle Street. This is the RI to scale.

It has a little hole in the roof just like this one has.

OK? So, let's try and build the tallest building in the world but

out of concrete, and let's do it in a pyramid structure because...

Where are we going to put it? There seems to be a lot of space here.

There's Green Park, there's St James's Park and there's

this thing called Buckingham Palace Gardens that seems to be unoccupied.

That's amazing, isn't it? That seems like a very likely spot.

Yeah, let's do it.

Let's have a go at this.

We'll have to ask the Queen. That's the first thing we'll have to do.

I think she'll be upset at losing her palace.

She's got a few palaces but is pretty much attached to this one, I'm sure.

So, we have to offer her space in this new building, that's what I'm thinking.

Of course, we seem to have wiped out half of Mayfair here and Belgravia and that kind of thing.

I guess that is the problem, isn't it?

Pyramids are great, they last for a long time, they can cope with the stress, that's all fantastic.

We have our structural head right on.

Basically, this is to scale now so this would now be the tallest building in the world, a pyramid

in the middle of London, which would be fantastic. It would be very impressive!

If you think about it, if you try to build it even higher, say twice as high, so we are up there now.

Think how big the footprint would have to be.

It would have to take over the whole of central London, and at today's

house prices, that would just be a mammoth planning task, wouldn't it?

That would only get you so far and even then, how high would we really get?

So, that's a real problem with pyramids. The plan area at the bottom that it takes up.

There's another problem with pyramids. This is a picture of Mount Everest here.

Mountains are essentially pyramids, aren't they?

They're peaked at the top and they have a wide base.

We can study them. Mount Everest is 10 times bigger

than this pyramid here, if this was the highest building in the world - 0.8 kilometres.

That's about eight kilometres high.

Nature builds mountains itself, so it builds pyramids, and they don't get bigger and bigger and bigger.

They sort of stay rather small.

Why is that? Let's have a look because that is odd.

You would have thought the geological processes in the Earth

would allow us to get much bigger mountains than that. But here is the problem.

This pyramid and that mountain are heavy - they are big objects.

That mountain is two or three trillion tonnes.

So, when it sits on the Earth's crust, and this, in case you were

about to ask and I'm sure you were, is a model of the Earth's crust. And then underneath, the mantle.

It is hot so we have the crust and the mantle here and it is hot rock, it is solid rock, but it is hot.

Over millions of years, a trillion tonnes of mountain sits on that hot rock and this is what happens.

It starts to sink. Why?

Why does solid rock behave like a liquid and let things sink in it?

That doesn't seem right but it turns out that, over millions of years,

if it is hot enough - and it is hot enough -

it flows like a liquid. The process of mountain building

on this planet is, things pushing stuff up - a geological process making mountains - and them sinking

back in, and the balance of those two forces determines the height of the mountains on this planet.

You would think, hold on a minute.

Surely you could get some enormous eruptions and get much bigger

mountains like this one, which is three times the size of Everest.

Three times the size of my model of Everest!

Let us think what would happen then.

It is much more than three times the weight, as you will know if

you listened to lecture one, and look at that.

It is sinking down and down, so you have much more mass being

pulled down by gravity and it keeps going down and it keeps going down.

The buoyancy forces, opposing these gravitational forces, mean this

has to sit much further down then you would expect and this will keep going down.

So, you can't just keep building bigger and bigger mountains and

hope to have for them to stay around because the rock behaves like a liquid and they sink.

You would think, "OK, why can't we do it on another planet with a lower

"gravitational field or strength, like Mars?"

Good question. And there it is.

Olympus Mons on Mars is three times taller than Everest so it is

bigger on Mars but it has a lower gravitational field.

Clearly, this balance of forces is correct but it is still just a pimple on the surface of Mars.

So, we can't build our way off the planet by building with big, heavy stuff.

We need a material that is strong and light. So something that has a high strength-to-weight ratio.

Let's think this through. I'm going to need a volunteer to help me.

Who? Er... Yes.

You, Sir, on the end.

Hello. What is your name?

-William.

-OK, William.

I've got something to show you here.

So, we want something strong and light. I've got two materials here and they are both strong

but we want to work out which one is stronger and lighter so it is a bit of a calculation.

A steel bar, there we go.

I want you to try and break it, bend it so you can't bend it any more.

Oh, that's cheating but fair enough.

-It is pretty strong, isn't it?

-Yeah.

No chance, right? What about this?

This is another material that is very strong. It is called a carbon fibre composite. Try and bend that.

Yeah. It's different, isn't it?

-Yeah.

-Which one of them has the best strength-to-weight ratio?

-I would assume it would be this one.

-Oh! I like your...

But how can you tell because it doesn't seem like a fair test because did they weigh the same?

-Not really.

-No and in order to work that out, you would have to work out how much you were tensing it.

So, what you'd like to see, wouldn't you...

-Yeah.

-..is the same weight objects?

So a piece of steel the same weight as that. That would be much easier?

-Yeah.

-Good thinking. So let's get something the same weight and let's

weigh it, in case people think it's not the same weight.

So here's the steel.

That is 145 grams. All right.

Now try and bend that. Go! Go!

You can make noises as well if you want. I do.

All right. If this one is worth 145 grams or thereabouts, we will then try and test that one again.

This one is 145 grams.

The same weight. Now bend this one.

No chance. Suddenly, your original assumption about

this one being the best strength per weight is absolutely correct.

-Yeah.

-Genius! Thank you very much.

Fantastic!

So, carbon composites are amazing.

They are strong but light and these are revolutionising people's lives.

Have a look at this.

'It's another golden route to the line for British cycling.

'The latest star is Jody Cundy.'

Jody Cundy, come on! Here he comes!

APPLAUSE

Jody, tell us about your credentials.

Well, I'm a double world champion, a multiple world record holder and

double Paralympic champion in track cycling, and that was me winning in Beijing.

-Wow!

-APPLAUSE

How much of it is you and how much of it is this marvellous material that your bike is made out of?

Well, I like to think a lot of it is me making the bike go fast

but the carbon fibre we have in the bikes really helps us go fast.

They are shaped aerodynamically so we cut through the air.

Even my leg is made of carbon fibre to cut through the air.

-Wow!

-The frame is made of carbon, the wheels are made of carbon, the

handlebars are made of carbon and the seat post.

Pretty much everything on the bike is carbon and it's basically there so

-we transfer all the power we have in our legs to make the back wheel go so we go forward.

-That's incredible.

Your leg is actually the cycling leg?

That's right. It's completely useless for walking in but it has a cycling cleat on the bottom just like any

-other shoe and it clips into my pedals.

-It's amazing, isn't it?

-Can I just see how light...?

-Yes, sure.

I want to see if I can lift it up with one finger.

APPLAUSE

This is an absolute thing of beauty, isn't it?

-Thank you so much for coming in.

-Not a problem.

-It is a real privilege to meet you.

-Thank you.

APPLAUSE

It's not just in Olympic sports or extreme sports but it is also everyday life.

This is a material that will affect every one of you.

I want to show you the latest aircraft from Airbus, the A380.

This is a double-decker plane.

20 per cent of this is carbon-fibre composite and this is only going to increase.

As the years go on, I'm pretty confident that in 10 years' time, 70 or 80 per cent of aircraft will

be carbon-fibre or other composites. We've brought some in from an actual A380.

This is part of the underwing component. We've got two bits of it here.

It is carbon fibres, so a bit like the graphite in pencils but made into a fibre

and then it is interwoven with a resin - a plastic - and that is why it is called a composite.

It is part fibre - carbon fibre - and part resin and this resin,

this plastic is the sort of thing you get with Araldite. Almost like a glue.

On their own they are not so useful but put them together

and you get this marvellously strong material.

I want to give you an experience of how strong these materials are.

I need a volunteer. Yes, you on the end with the Christmas hat.

APPLAUSE

What's your name?

-Katie.

-Katie, are you strong?

-Er, yeah...?

-OK.

-Have you got a bad back?

-No.

-Good.

OK. I just want you to lift this up and I'll tell you what to do later.

Do you think you'll be able to lift that up?

-Yeah.

-Oh!

Actually, it's quite light, isn't it?

-Yeah.

-You could look a little bit more surprised if you like!

No. Don't worry. Are you surprised how light that is?

-Yeah.

-It's incredible.

That's an enormous piece of stuff and it's very light.

In fact, it's so light... Can you continue to hold it?

Are you getting strain? No, it's so light.

I can lift this up with one hand.

It's the size of a wardrobe and yet... All right! Come on, guys!

-APPLAUSE

-OK. Thank you very much.

-I wasn't going to get you to smash it because there has been enough smashing, hasn't there?

-Yeah.

Thank you very much.

So the key to this material is its strength-to-weight ratio.

It's a fantastic material for that.

So, could we use these materials to build ourselves off the planet?

That is the question. And make things that are really, really tall?

Let us defeat gravity once and for all with these light materials.

Earlier, here, we were looking at the Earth and we worked out that we'd have to get 36,000 kilometres

over here before we could really get out of the grips of gravity.

What we want to try and do is build a building 36,000 kilometres high.

We'd already worked out we'd need something with high strength-to-weight ratio.

So, let's see how all the materials we have so far come across do on that rating. Oh...!

Have you still got your common sense turned on?

That is a very silly material. All right. This is a scale model of

the Burj Khalifa, the tallest building in the world,

scaled down, so it is 0.8 kilometres high - half-a-mile high.

If we were to build a building out of steel, pure, solid steel and keep

going up, we would get up to 4 kilometres high.

So, we could build a building 4 kilometres high no problem at all.

If we use concrete, we would get up to 4.7 kilometres high.

That is incredible. It is insane!

It really makes the current buildings we live in look puny.

Actually, modern buildings are often built with a combination of steel and concrete so if you do

the calculations, you could probably get up to 5 kilometres with a combination of these two materials.

5 kilometres high for the materials that we know about.

What about carbon fibre?

What about this fantastic material with strength-to-weight ratio that is much better? Let's see.

It's actually extremely high.

It's really impressively high.

We actually have to go higher and higher... Higher than the steel, higher than the concrete,

higher than the combination of steel and concrete

and even higher and higher and higher to 7 kilometres.

We could build a building 7 kilometres high with carbon-fibre composite.

A material it is really light but strong, and the advantage is there isn't this huge mass bearing down

on it because it is so light and yet it is really strong so it can withstand a lot of its own weight.

The other brilliant thing is the view is fantastic up here. Amazing!

7 kilometres is really impressive. Let's say we could really make some advances.

We could get to maybe 10 kilometres if we bettered the design.

Maybe we could get to 100 kilometres in the next century or so. It still wouldn't be anywhere near

36,000 kilometres which we would need to build ourselves off the planet

and that is what we want to do, right?

That seems like a really great thing to do. Yet, hm...

So, is there another way to think about this problem?

ALL: Behind you!

Crikey! Well!

But, yeah, you're right.

I can see your point you're trying to make with that, because spiders

don't build up, they've got more sense than that. They build down.

They go up to the top and then they come down on a little fibre.

So, that gives me an idea.

Why can't we do the same thing with this problem?

Just turn the whole thing upside down. Let's not build up, let's build down.

Or, not build, let's send a cable down.

If I am here orbiting the Earth as a satellite, OK?

And then I get a cable and I send it down to Earth like this,

and I just keep sending it down and I keep going and

I keep going and I keep going for 36,000 kilometres...

And then when we get to the bottom, we tie it off.

I know that sounds ridiculous but just go with me on this one.

Now we've got a cable from a satellite orbiting the Earth to the Earth's surface.

Now, attach an elevator to that and what do you have but a space elevator?

And we could just get into it and go up to space.

How fantastic would that be?

It would be brilliant.

The thing is, of course, when you're paying

a cable down, there's huge gravitational forces

pulling it to Earth because of the enormous weight of the cable.

Again, you'd need something with very high strength-to-weight ratio, wouldn't you?

How strong does it have to be? If you do the calculations,

it turns out that you need something that would be so strong

that if you had a 1mm-thick fibre - something a bit like a thread - it would have

to suspend the whole audience, which is 20 tonnes. That seems like quite a big task.

Well, I've been thinking about this, we do have fibres that are very strong, don't we?

As a scientist, it is a very competitive field and often

I get the feeling that people want to take a pot-shot at me.

So, like a lot of other scientists worried about this, I have a body double.

Occasionally, I send the body double to conferences instead of me, just to see what happens.

The other week, this is what happened.

I knew it!

I knew they were after me.

Luckily, they mistook my body double for me and here he is. He survived.

APPLAUSE

Now, the reason he survived - and it is not really him because he is plastic, I know that!

But he has one of my shirts on and I didn't want him to get that hurt

so I put on a Kevlar bulletproof vest.

You can see that the bullets went in here

and in through here, but they did not make it through the Kevlar.

These bits on the outside are sort of nylon outer layers

and inside is the Kevlar. It is an extremely strong fibre.

I will show you where it is.

That is Kevlar.

It is an extremely fine weave

and extremely strong fibre.

So what is Kevlar?

It is a set of molecules that have been assembled molecule by molecule at the atomic scale.

Its strength really is very close to the atomic strength of those molecules together.

So, you are breaking atomic bonds to break this material and that means that it is extremely strong.

Is it strong enough, though, to build the cable for the space elevator?

It turns out to be not.

It would only support a couple of people with a thickness of that fibre.

Although Kevlar's fantastic for saving lives,

and it really is the material of choice, it isn't good enough for what we want it to do.

That is a bit of a problem, but recently there have been

some material science discoveries that have kind of given us hope.

It turns out that the ingredients for this material that has given us hope,

you've experienced yourself at every birthday you've ever had.

I want to ask if there is anyone here whose birthday is this week?

It is your birthday this week? All right.

Do you mind coming down?

Hello. What is your name?

-Catherine.

-Catherine, and it is your birthday this week. What do you have on your birthday? A cake!

Here we go! A birthday cake for you for next Monday.

Now, would you believe that the ingredients for a great new material are here?

Where are they, though?

Are they in the cake, the icing, the ribbon, the wax?

Well, let me take a sample of it.

And now you can blow out the candles if you like.

Happy birthday!

So, on this glass slide I collected some of the ingredients for this material.

It turns out that,

until 10 or 20 years ago, we thought that there were only two forms of carbon -

diamond, which is superhard and translucent

and there was graphite which we use in pencils. We thought that was it.

Then people started looking around and realised that carbon can arrange itself in other amazing ways.

One of them we found in the soot of candles, which is an incredible place to find it.

In here are molecules that look like this.

They are called buckyballs and they are a different way

of arranging carbon and they are really beautiful things.

And if you use these

and you re-combine them, you can make things like this and these are called carbon nanotubes.

This is a fantastically strong

and light material. The reason is this. It's mostly carbon. Well, it's only carbon.

Carbon is a really light element, one of the lightest elements in the periodic table so your ingredients

are really light. The bonds between them are really strong.

It is a really strong structure and in the middle, there is nothing.

So there is even less density. These things...

You all know what it's like when you have a piece of paper and it waves about

and you wrap it into a column and suddenly it is strong and stiff.

You've got the same thing going on here.

At a molecular level, this thing is as an extraordinarily strong structure.

In fact, it is theoretically, when you do the quantum mechanics calculations,

you find this has the strength we need

to make the space elevator cable.

But, of course, they are tiny things. Let me show you how small they are.

I can't really show you how small they are because all I can show you is a jar of them.

They are individual little nanoscales.

This is at the scale of one billionth so they are a billion times smaller than this.

So, the big challenge is then

to join these up into one long thread and that is really difficult.

Then, to get those threads into a twine and then into a cable.

If you are familiar with suspension bridges, you've got small bits of steel

into a twine, bigger bits of steel, bigger, bigger, bigger.

All wrapped around. So that is a cable.

Let me tell you how far materials scientists have got. They can make nanotubes.

Here are some of the first ever in the world examples of threads made with nanotubes.

This really is an amazing sample.

This was made in the Windle lab in Cambridge.

It really is these joined together in a thread. Let me show you under the microscope.

It is an incredibly exciting moment for everyone because we had all been hoping this material could be made

and this really is the jump between theory - the theoretical material science -

to the practical material science and then to the engineering.

At the moment, it is not there yet, but it is going to happen.

People are going to get better and better at making this into that material.

When they do, we are going to have a material that can make a space elevator.

If we've got the materials that we can make this cable out of,

and that was the big challenge, the rest looks pretty straight forward.

Let me talk you through what we would have to do.

We'd have to get up into space, get a satellite that was orbiting the Earth,

geostationary orbit 36,000 kilometres.

Then we have to work out a way of making the material up here

because we wouldn't want to get it up here all the time.

So we make it up here and we start paying out this cable down, 36,000 kilometres down.

Then we tether it to the Earth.

You can see where it hits is in the ocean.

We want it on the equator and we want it in the ocean because we want

to tether it to a boat so that if there is any movement, it is taken up by the viscosity of the sea.

Then... Of course, you are all thinking this.

All of it would collapse under its own gravitational weight back to the Earth.

Good thought. What we would have to do is kind of have a counterweight.

So we would send a piece of material this side which exactly

has the counterweight of the force going in so the whole thing is in balance.

Now what happens is that you decide you want to go to space. Any of you.

So, you get a boat to the docking station and you get on the elevator

and you come up 36,000 kilometres and you hit and suddenly you are weightless.

APPLAUSE

How fantastic would that be?

Our parents' generation went to the moon. They gave that as a present to us

and it was an incredible achievement. We have got to live up to that.

We have got to do something just as good and give something to the next generation and this, I think, is it.

This is our challenge for our generation.

This is what is left over for us to do.

To make mass space transport via an elevator possible for everybody.

So, let's do it! Come on, guys, let's just do it!

Don't you think?

ALL: YES!

So, I hope you've enjoyed these lectures about scale and materials.

We've seen that everything changes as you get smaller.

Things get superstrong.

You can survive enormous falls, you can engineer materials to be incredible.

You can devise invisibility shields.

And ants are superstrong when they are small and hamsters are superstrong because they are small

and they can survive these enormous falls because of their size.

But we get to live longer than them because we are large.

So it all depends on how big you are.

Size really does matter and I hope that you've enjoyed this tour

through the scale of the universe and life.

Thank you very much for listening.

APPLAUSE

Subtitles by Red Bee Media Ltd

E-mail [email protected]