0:00:13 > 0:00:17CHEERING AND APPLAUSE
0:00:25 > 0:00:27Thank you very much.
0:00:27 > 0:00:32My name is Mark Miodownik, I'm a material scientist from King's College, London.
0:00:32 > 0:00:36Today we're going to talk about big stuff! Look at this stuff.
0:00:36 > 0:00:38Look at this bolt.
0:00:38 > 0:00:40Who could need a bolt that big?
0:00:40 > 0:00:44And this stuff here. We're going to talk about skyscrapers,
0:00:44 > 0:00:49mountains and planets, huge things.
0:00:49 > 0:00:52We're going to see that matter behaves on the big scale
0:00:52 > 0:00:56every bit as strangely as it does on the micro, tiny scale.
0:00:56 > 0:01:03In the previous lectures, we talked really about how different forces dominate at different scales.
0:01:03 > 0:01:07At the big scale, the force that we're going to need to worry about,
0:01:07 > 0:01:10the one that's going to dominate everything, is gravity.
0:01:10 > 0:01:14It's our invisible enemy.
0:01:14 > 0:01:16So how do we beat it?
0:01:16 > 0:01:18How do we make big things?
0:01:18 > 0:01:20This is a big thing. This is a mountain.
0:01:20 > 0:01:23It's huge. Look at it.
0:01:23 > 0:01:26Absolutely huge. Or is it?
0:01:26 > 0:01:29It all depends on the size and scale at which you look at it.
0:01:29 > 0:01:36If I zoom out now, now I'm the size of a planet, and I look down, well, mountains aren't so big any more.
0:01:36 > 0:01:38When things are big,
0:01:38 > 0:01:40it changes everything.
0:01:40 > 0:01:43You suddenly realise that
0:01:43 > 0:01:45all the rules are off.
0:01:45 > 0:01:49Matter behaves in a totally different way.
0:01:49 > 0:01:51I want to get you used to that idea.
0:01:51 > 0:01:56I'm going to need you to turn off your common sense in order to understand that kind of thing.
0:01:56 > 0:01:59Your common sense is really going to interfere.
0:01:59 > 0:02:04So first of all, let's get a feel for how gravity can affect big things.
0:02:04 > 0:02:07So I've got a material here, and it's a liquid.
0:02:07 > 0:02:10Who believes me that this is a liquid?
0:02:13 > 0:02:15OK, so you've still got your common sense turned on.
0:02:15 > 0:02:19I'll try and turn it off for you. Obviously, liquids don't do this...
0:02:19 > 0:02:24usually, do they? This feels very much like a solid.
0:02:24 > 0:02:28But I hope to prove to you, as the lecture goes on, that this is a liquid.
0:02:28 > 0:02:33I'm just going to leave it there for the moment. You keep an eye on this stuff.
0:02:33 > 0:02:35We'll come back to that.
0:02:35 > 0:02:37Here is another bonkers, mad liquid.
0:02:39 > 0:02:43This is one of my favourite liquids of all time - mercury.
0:02:43 > 0:02:48Gosh, who loves mercury? It's just the strangest stuff, isn't it?
0:02:48 > 0:02:54This... What's so strange about mercury is it's a metal but it's also a liquid at room temperature.
0:02:54 > 0:02:57Mercury is a heavy liquid. What does that mean, heavy?
0:02:57 > 0:03:01Well, I'll illustrate what I mean by heavy. This is a cannonball.
0:03:01 > 0:03:03That's definitely heavy.
0:03:04 > 0:03:07Gravity, this invisible force, pulled it down.
0:03:07 > 0:03:11Did you see that? You're probably used to that, aren't you? OK, let's see.
0:03:11 > 0:03:13Heavy cannonball, meet heavy liquid.
0:03:16 > 0:03:19We'll take that off. What's going to happen here, eh?
0:03:19 > 0:03:22Is it going to go right to the bottom?
0:03:27 > 0:03:30Wow! That's incredible, isn't it?
0:03:30 > 0:03:32A floating cannonball.
0:03:32 > 0:03:35Let's hear it for the cannonball!
0:03:35 > 0:03:39APPLAUSE
0:03:39 > 0:03:44All right, so that's heavy things, things where gravity is really playing a massive force.
0:03:44 > 0:03:47Now I'm going to show you a material that goes completely the opposite direction.
0:03:47 > 0:03:50I have here the lightest solid in the world.
0:03:50 > 0:03:54It's so light, you can't hardly see it.
0:03:54 > 0:04:02Can you see that? This stuff is called aerogel, and it's 99.8% air.
0:04:02 > 0:04:05It's only 0.2% solid.
0:04:05 > 0:04:11In fact, you can hardly see where it ends and the air begins because there's only 0.2 difference.
0:04:11 > 0:04:13It's got this blue tinge, have you noticed that?
0:04:13 > 0:04:16That's because it's a foam. It's a glass foam.
0:04:16 > 0:04:20The holes in that glass foam are so small that they
0:04:20 > 0:04:25scatter light, in the same way that light is scattered in the sky.
0:04:25 > 0:04:29So you're seeing it's blue, for the same reason that the sky is blue.
0:04:29 > 0:04:31There's no pigment in there.
0:04:31 > 0:04:36So this is as close as you'll ever get to holding a piece of sky in your hand.
0:04:36 > 0:04:38It's almost completely sky.
0:04:40 > 0:04:42You think, "That's incredible, 99% air.
0:04:42 > 0:04:45"What could anybody possibly want with a material like that?"
0:04:45 > 0:04:49It turns out that NASA use this to collect space dust.
0:04:49 > 0:04:53Absolutely amazing, isn't it?
0:04:53 > 0:04:57So, I think you have to give a big round of applause for aerogel, the lightest solid in the world.
0:04:59 > 0:05:01How are we doing with our common sense?
0:05:01 > 0:05:04It's looking less like a solid now, isn't it?
0:05:04 > 0:05:06Let's see how big we can build.
0:05:06 > 0:05:12This is the Burj Khalifa, the tallest building in the world.
0:05:12 > 0:05:18It's 0.8 kilometres high, so that's half a mile high.
0:05:18 > 0:05:20Of course, I look quite big next to it, don't I?
0:05:20 > 0:05:22I look like a giant.
0:05:22 > 0:05:25But actually, if you shrunk me down, this is what I'd look like.
0:05:25 > 0:05:27It's really high!
0:05:27 > 0:05:30It's absolutely a magnificent building.
0:05:30 > 0:05:34But, well, what happens if I'm the size of Everest?
0:05:34 > 0:05:38Now, here I am, I'm a giant.
0:05:38 > 0:05:42If I was to look at the Burj Khalifa now, that's how high it would be.
0:05:42 > 0:05:44It's down here, tiny.
0:05:46 > 0:05:49So why can't we build anything bigger?
0:05:49 > 0:05:50That seems pathetic.
0:05:50 > 0:05:53We've gone to the moon, and yet that's all we're building.
0:05:53 > 0:05:57We've got a model here of the Earth.
0:05:57 > 0:06:00Here's England. Here's where we are.
0:06:02 > 0:06:06If we were to put on a scale the Burj Khalifa, you wouldn't be able to see it.
0:06:06 > 0:06:09We'd need a microscope. It's down there but we haven't seen it.
0:06:09 > 0:06:14If you were to put the mountains on here, again, as you saw with the pictures of the Earth, they're tiny.
0:06:14 > 0:06:20So this Earth, you can see, has this incredible roundness, it's all very, very smooth.
0:06:20 > 0:06:26That's because the Earth exerts an enormous gravitational field. It's huge.
0:06:26 > 0:06:31This enormous mass is exerting a force on you, me, that cannonball.
0:06:31 > 0:06:34How far do we have to go to get out of its hold?
0:06:34 > 0:06:36I'll show you.
0:06:36 > 0:06:40I'm going to just say, if we were to build a building this high...
0:06:40 > 0:06:43Not quite this high, a bit higher.
0:06:43 > 0:06:46And a bit higher, and a bit higher,
0:06:46 > 0:06:53and a bit higher, and a bit higher, and a bit higher, and a bit higher, and a bit higher,
0:06:53 > 0:06:55and a bit higher!
0:06:55 > 0:06:58If we were to build a building, and this is the scale,
0:06:58 > 0:07:03if we built a building 36,000 kilometres high,
0:07:03 > 0:07:07we'd be at what's called a geostationary orbit.
0:07:07 > 0:07:11So satellites, communication satellites up there,
0:07:11 > 0:07:13they stay in a fixed position with regard to the
0:07:13 > 0:07:17Earth as they satellite around, and they aren't sucked back into Earth.
0:07:17 > 0:07:21So if we can get up there, 36,000 kilometres away from the Earth,
0:07:21 > 0:07:25then we can escape the Earth's gravitational field, this tyranny of gravity.
0:07:25 > 0:07:28So why haven't we done that?
0:07:28 > 0:07:31Why haven't we managed to do anything close to that yet?
0:07:31 > 0:07:35I'm going to need a few volunteers from the audience to help me.
0:07:35 > 0:07:37One there. A lady there.
0:07:37 > 0:07:39Let's get a guy, yeah, go on.
0:07:39 > 0:07:43And one more. Yes. Why don't you come down?
0:07:43 > 0:07:47APPLAUSE
0:07:47 > 0:07:50We're going to have a competition now, and there will be prizes.
0:07:50 > 0:07:53The competition is to escape the Earth's gravity.
0:07:53 > 0:07:55LAUGHTER
0:07:55 > 0:08:02So, what I'm going to try and do is, obviously you're going to try and jettison off into space.
0:08:02 > 0:08:06If you make it as far as the roof, we'll open it for you.
0:08:06 > 0:08:10So don't worry about that. Don't limit your ambitions. Are you ready?
0:08:10 > 0:08:15OK, we'll do a countdown, everybody. Three, two, one. Go!
0:08:15 > 0:08:20Oh... Oh, you did it twice! We'll have to consult the referee.
0:08:20 > 0:08:23They're letting that go.
0:08:23 > 0:08:28All right. But let's have a look at the action replay. Up they go.
0:08:31 > 0:08:33It was the old back flips, I think that got it for you.
0:08:33 > 0:08:36Well done. Technique!
0:08:36 > 0:08:39APPLAUSE
0:08:39 > 0:08:44OK, that was really sporting of them, but it wasn't very impressive, was it?
0:08:44 > 0:08:46Half a second is all we could...
0:08:46 > 0:08:53And they're no better or worse than most of us. So gravity is this incredible tyranny on our lives.
0:08:53 > 0:08:55It's constantly gluing us to the floor.
0:08:55 > 0:09:02That seems really annoying to me. So I started thinking, let's try and work out how to levitate.
0:09:02 > 0:09:04So here we go. I thought,
0:09:04 > 0:09:07"We should be able to make a levitation machine."
0:09:07 > 0:09:11Got in touch with some material scientists who had some ideas about this, and they gave us
0:09:11 > 0:09:15some of this material, which is called a superconductor.
0:09:15 > 0:09:18When you cool superconductors down with liquid nitrogen -
0:09:18 > 0:09:24so we're going to get down to minus 193 degrees centigrade -
0:09:24 > 0:09:30then these superconductors, they repel magnetic fields.
0:09:30 > 0:09:34So the idea is this. Gravity pulls magnet down, and we repel magnetic
0:09:34 > 0:09:39field with the superconductor, and they equal each other, and we get the magnet to levitate.
0:09:41 > 0:09:45All right, let's see if it works, though. Is it working?
0:09:45 > 0:09:47Oh-ho-ho-ho!
0:09:47 > 0:09:49APPLAUSE
0:09:54 > 0:09:56I know what you're all thinking.
0:09:56 > 0:09:59You're thinking there's a tiny little thread, aren't you? I know.
0:09:59 > 0:10:04So, look, just to prove to you that there's isn't anything underneath or over the top...
0:10:04 > 0:10:06Nothing over the top. And...
0:10:06 > 0:10:09AUDIENCE GASPS
0:10:09 > 0:10:13- APPLAUSE - Oh, yes.
0:10:13 > 0:10:18The thing about that was you had a magnetic field opposing the gravitational field exactly.
0:10:18 > 0:10:24Turns out that, as the magnet gets bigger and bigger and bigger, that gets harder and harder to do.
0:10:24 > 0:10:31So I thought, "I'll invent a levitation device that can levitate me".
0:10:31 > 0:10:39So off I went to my garden shed, and I came up with a levitation device,
0:10:39 > 0:10:44and this is the world premiere of this device. I think you're all going to be very impressed.
0:10:44 > 0:10:47This really could be the future of us getting off this planet.
0:10:47 > 0:10:50- Do you want to see it?- ALL: Yes.
0:10:50 > 0:10:53You don't sound that interested.
0:10:53 > 0:10:57- Come on, do you want to see it? - ALL: Yes!
0:10:57 > 0:11:02- OK. - DRUM ROLL
0:11:09 > 0:11:12You're clapping but I know you're not that impressed.
0:11:12 > 0:11:14But just bear with me on this one.
0:11:14 > 0:11:18This is a levitation device. I'm on the floor, I'm stuck to the floor.
0:11:18 > 0:11:21Now I'm not. Right?
0:11:21 > 0:11:25Before, we had a magnetic field repelling my gravitational force.
0:11:25 > 0:11:32But now, inside this piece of wood, as we call it in the technical...
0:11:32 > 0:11:38There's an elastic force field which is exactly matching my gravitational field.
0:11:38 > 0:11:41So there's an elastic force field in there.
0:11:41 > 0:11:45At the atomic scale, the atoms are being pulled apart exactly to match
0:11:45 > 0:11:48by gravitational force. So this is fantastic.
0:11:48 > 0:11:51And it's not just happening to me, it's happening to all of you now.
0:11:51 > 0:11:56All of you are sitting down and gravity is still acting on you.
0:11:56 > 0:12:00Gravity isn't this force that just acts, switches on when you're falling. It's acting on you now.
0:12:00 > 0:12:04It's pushing you down to the ground, and if there wasn't an elastic
0:12:04 > 0:12:09force field underneath your bum now - let's all just think about our bums - no, not too much!
0:12:09 > 0:12:13That's enough! So it's that elastic force field underneath
0:12:13 > 0:12:17your bum, so it's the cushion and it's the floor, isn't it?
0:12:17 > 0:12:23If you think about it, the floor in here, in this whole auditorium, is having to put up with quite a lot.
0:12:23 > 0:12:27Before you lot came in here, there wasn't an elastic force field, and
0:12:27 > 0:12:31now there's a massive elastic force field in here holding you all up.
0:12:31 > 0:12:35So that's great, isn't it? Buildings just do that for free. Or do they?
0:12:35 > 0:12:42Let's get a feeling for how much elastic force field they're having to put up with now, in this room.
0:12:42 > 0:12:50OK, so how do I do that? Anyone got any ideas how to calculate the total gravitational force acting down now?
0:12:50 > 0:12:52Anyone? You've got an idea.
0:12:52 > 0:12:55- A force meter?- A force meter, yes.
0:12:55 > 0:13:03- And what do we call force meters, in the parlance, in the bathroom perhaps? Anyone? Yes?- Scales.
0:13:03 > 0:13:05Scales! You, you're good.
0:13:05 > 0:13:07So it's a scale.
0:13:07 > 0:13:12If we're going to measure this audience, we need a scale that will weigh you all, don't we?
0:13:12 > 0:13:17So let's get in a big scale. What we thought we could do is get you all to sit on this scale.
0:13:17 > 0:13:20We borrowed these from Shrek.
0:13:20 > 0:13:22He has them in his bathroom and he let us...
0:13:22 > 0:13:25He's on a diet at the moment.
0:13:25 > 0:13:28He's obsessed with his weight. What we want to do is try and measure
0:13:28 > 0:13:31the audience, how much gravitational force from the audience.
0:13:31 > 0:13:34So I need some help with this.
0:13:34 > 0:13:37I'm going to try and weigh as many of you as I can.
0:13:37 > 0:13:41But first of all I'm going to start with one. Can I get someone in the front row who's brave enough?
0:13:41 > 0:13:43Are you brave enough to come...?
0:13:43 > 0:13:46How do you feel about your weight? Are you sensitive about it?
0:13:46 > 0:13:48- LAUGHTER - No, you're not. What's your name?
0:13:48 > 0:13:50- Tomasz.- Tomasz?- Yes.- OK, brilliant.
0:13:50 > 0:13:54So, Tomasz, I'm just going to zero the scales. Off you go.
0:13:54 > 0:13:56Let's see, how much do you weigh?
0:13:56 > 0:14:0041 kilos. Is that about right? Good.
0:14:00 > 0:14:02Now let's see if we can get some more on.
0:14:02 > 0:14:04Can we get two more of you on there?
0:14:04 > 0:14:06Is that possible? Are you two up for that?
0:14:06 > 0:14:09All right, come on, then.
0:14:09 > 0:14:14You two get on there, and budge up a bit if you don't mind.
0:14:14 > 0:14:17How are we doing? 128 kilos.
0:14:17 > 0:14:23Do you think you three will be able to get on there? All right.
0:14:23 > 0:14:25How are we doing? 309 kilos.
0:14:25 > 0:14:28What about you two? Are you going to make it on there?
0:14:28 > 0:14:32You can get on the edge bits, as well. What about you guys?
0:14:32 > 0:14:34Are you up for it? So, you four.
0:14:34 > 0:14:38Let's see if we can get four more of you on.
0:14:38 > 0:14:41There's a game called sardines that's very similar to this!
0:14:43 > 0:14:48This is good. We're up to 600 kilos.
0:14:48 > 0:14:49Can we get any more?
0:14:49 > 0:14:53Come on, let's get the whole of this row on if we can. Is that possible?
0:14:53 > 0:14:56How are you guys feeling? Are you all right? Is there room?
0:14:56 > 0:14:59- No!- Come on!
0:14:59 > 0:15:02There's a bit of space over here.
0:15:02 > 0:15:06You came up with this idea, so you should be at the front. Brilliant.
0:15:06 > 0:15:08And can you get into that little corner there?
0:15:08 > 0:15:13You'll all get to know each other. This is all very friendly. Oh, no!
0:15:13 > 0:15:16Is there not enough room for you guys at the back?
0:15:16 > 0:15:19Is there a little bit of room there? OK, hold on, guys, just two seconds.
0:15:19 > 0:15:23So we've got 700... Are we on?
0:15:23 > 0:15:27771, no, let's say 775 kilos.
0:15:27 > 0:15:31For how many kids? Oh, I didn't count.
0:15:31 > 0:15:34- LAUGHTER - Did anyone count?
0:15:34 > 0:15:37All right, let's get off, guys. Thank you. A big round of applause.
0:15:37 > 0:15:421, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16.
0:15:42 > 0:15:4416 kids, I think.
0:15:44 > 0:15:48So that turns out to be, has anybody done that calculation in their head?
0:15:48 > 0:15:50Average weight of kid?
0:15:50 > 0:15:5648 kilos per kid. So let's say 50. And there are about 400 of you here.
0:15:56 > 0:15:58So that means...
0:15:58 > 0:16:05A bit of mental calculation going on in my head now... 20 tonnes.
0:16:05 > 0:16:07So you weigh 20 tonnes.
0:16:07 > 0:16:09That's pretty amazing, isn't it?
0:16:09 > 0:16:12So before you came in here, this poor building was minding its own business,
0:16:12 > 0:16:16just having a lovely Saturday afternoon, having a bit of a rest,
0:16:16 > 0:16:22then it had to put up with 20 tonnes of you, and it's holding you up like this, and we never really asked it.
0:16:22 > 0:16:27So it's produced an elastic force field of 20 tonnes just like that.
0:16:27 > 0:16:32Next time you go out and buy a really heavy, big, new, flat-screen TV, think about the building.
0:16:32 > 0:16:39The poor old building never got asked if he wanted a big flat-screen TV that weighs half a tonne.
0:16:39 > 0:16:42And it has to put up with holding it even when you're asleep.
0:16:42 > 0:16:46Those of us in the Society For Protection To Cruelty To Buildings
0:16:46 > 0:16:51are quite concerned about this accruement of very heavy technology in the home.
0:16:51 > 0:16:56OK, so it turns out that buildings are quite good at coping with this.
0:16:56 > 0:17:01So why can't we just build ourselves off the planet?
0:17:01 > 0:17:06I'm going to need a couple of volunteers who kind of, who have ambitions to work in engineering.
0:17:06 > 0:17:10The hands are still up. Fantastic, I love that!
0:17:10 > 0:17:12Let's have you, Sir, there.
0:17:12 > 0:17:15Yes, brilliant. And, Madam.
0:17:15 > 0:17:17- APPLAUSE - All right, what's your name?
0:17:17 > 0:17:19- Charlotte.- Charlotte. And your name?
0:17:19 > 0:17:21- Dennis?- Innes.
0:17:21 > 0:17:23Innes. Innes and Charlotte, OK.
0:17:23 > 0:17:26In this game, you do all the work and I get to talk.
0:17:26 > 0:17:29Is that all right? Anyway, we're going to try
0:17:29 > 0:17:33and build ourselves off the planet, well, at least the first few steps.
0:17:33 > 0:17:35And here they are. So we've got the first step.
0:17:35 > 0:17:38This is my anti-gravity machine, which we now agree is genius.
0:17:38 > 0:17:43If you could just add, can you grab some of those and add the next step?
0:17:43 > 0:17:45That's what we want to do.
0:17:45 > 0:17:50I want to basically get the idea of building us off the planet, so you put two on there, fantastic.
0:17:50 > 0:17:54I think if we can get a slat across, yes, that would be brilliant.
0:17:54 > 0:17:59I'll put that on. I do the easy bit.
0:17:59 > 0:18:04Hooray, I'm up. One further bit away from the planet.
0:18:04 > 0:18:09It's like an enormous game of Jenga, although I hope it won't end the same way.
0:18:09 > 0:18:14Look, guys, you've done a fantastic job. Here we go, up I go, and we could just keep going, couldn't we?
0:18:14 > 0:18:20If you weren't getting tired and had infinite energy and we had infinite materials. That seems reasonable.
0:18:20 > 0:18:23Well, thanks very much for helping me with that, guys.
0:18:23 > 0:18:24I really appreciate that.
0:18:24 > 0:18:27APPLAUSE
0:18:27 > 0:18:31What's stopping us just keeping on going?
0:18:31 > 0:18:36Hm. Well, there is a problem.
0:18:36 > 0:18:39There is a problem.
0:18:39 > 0:18:44In order to tell you about that problem, I'm going to invite some friends to help me work it out.
0:18:44 > 0:18:49# F-O-R-C-E Let's learn about gravity
0:18:49 > 0:18:53# F-O-R-C-E Let's learn about gravity
0:18:53 > 0:18:58# F-O-R-C-E Let's learn about gravity. #
0:18:58 > 0:19:00Five, six, seven, eight.
0:19:09 > 0:19:11APPLAUSE
0:19:26 > 0:19:30Well done, guys. Fantastic.
0:19:33 > 0:19:35OK, well done, fantastic.
0:19:35 > 0:19:38Now, who was at the top? What's your name?
0:19:38 > 0:19:40- Keira.- Keira, you were at the top.
0:19:40 > 0:19:46How was it at the top? Did you feel an enormous force on your shoulders?
0:19:46 > 0:19:51No. Did you feel yourself pressing down on other people? Yes, you did.
0:19:51 > 0:19:53And how was it at the bottom?
0:19:53 > 0:19:57You guys were at the bottom, I was at the bottom.
0:19:58 > 0:20:01Do you guys take it in turns? What goes on?
0:20:01 > 0:20:03Nah, we've got all the weight.
0:20:03 > 0:20:07Basically, this is the problem, isn't it? As you build things
0:20:07 > 0:20:11higher and higher, you guys are always going to have to take all the weight that goes above you.
0:20:11 > 0:20:15- Yes.- That just gets worse and worse.
0:20:15 > 0:20:18So if we put another tier on top, which we're about to do, aren't we?
0:20:18 > 0:20:20- LAUGHTER - Oh, no, just joking!
0:20:20 > 0:20:23We'll just run that through again,
0:20:23 > 0:20:27cos we want to get the hang of it, and I want everyone to look at these guys' faces on the bottom.
0:20:27 > 0:20:29Not the top - she gets all the glory.
0:20:29 > 0:20:31Look at the people doing the work at the bottom.
0:20:31 > 0:20:33Let's go for it again, guys.
0:20:33 > 0:20:36Five, six, seven, eight.
0:20:46 > 0:20:48APPLAUSE
0:20:58 > 0:21:00Let's hear it for these guys.
0:21:09 > 0:21:15So what we saw there is, if buildings had emotions,
0:21:15 > 0:21:20right, all the bricks and stones at the bottom would be going "Arrrgh!"
0:21:20 > 0:21:24all the time, wouldn't they? They've got to hold the whole building up.
0:21:24 > 0:21:29As the building gets higher and higher and higher, their load doesn't get any better.
0:21:29 > 0:21:33They have to take more and more weight, so gravity is
0:21:33 > 0:21:36constantly working, even in static structures like this.
0:21:36 > 0:21:42What we have to do is find the materials that can cope with that kind of pressure.
0:21:49 > 0:21:50Phew!
0:21:50 > 0:21:56OK, so remember, we're trying to work out what makes materials strong.
0:21:56 > 0:21:58We're going to do a test now.
0:21:58 > 0:22:02I need a volunteer to help me work out what are strong materials.
0:22:02 > 0:22:06Let's take you over there. Fantastic.
0:22:12 > 0:22:15- What's your name?- Natasha. - Natasha, OK.
0:22:15 > 0:22:19- Are you up to helping me work out which are strong materials that we need for building?- Yep.
0:22:19 > 0:22:24If you go round that corner there, I'll come round here, I'll join you.
0:22:24 > 0:22:32What we're going to do is, we've got here a dresser like you might have at home, with some objects on it.
0:22:32 > 0:22:36We're going to try and test them to destruction.
0:22:36 > 0:22:41To get you in the right mood for this, I want you to think
0:22:41 > 0:22:46about the most furious moment in your life and how you felt,
0:22:46 > 0:22:53and in that moment you thought, "Gosh, I really want to throw this ball at that", didn't you?
0:22:53 > 0:22:56I'm also going to get you to put some safety goggles on.
0:22:56 > 0:23:01Is that all right? So you're holding that thought, furious, and of course
0:23:01 > 0:23:04you could never do this at home, you'd never do this at home.
0:23:04 > 0:23:09- But here you can do it. Is this going to be the happiest moment of your life?- Yes!
0:23:09 > 0:23:12It's going to be a competition, which is always the way with me.
0:23:12 > 0:23:15You're going to get three balls, I'm going to hand them to you, and I'm
0:23:15 > 0:23:18going to get three balls, and we'll see who can smash the most.
0:23:18 > 0:23:23- OK.- That sound fair? I'm thinking furious thoughts, you're thinking furious thoughts.
0:23:23 > 0:23:25- Let's see which materials can survive.- OK.
0:23:25 > 0:23:28Off you go, you go first.
0:23:35 > 0:23:40OK, wow. All right, I'm going to do the same.
0:23:40 > 0:23:47Not too bad. One each. Off you go.
0:23:49 > 0:23:53Wow, you're quite angry inside!
0:23:53 > 0:23:57LAUGHTER
0:23:57 > 0:24:00All right, last go.
0:24:00 > 0:24:02Oops.
0:24:02 > 0:24:07I'm actually quite nervous now.
0:24:07 > 0:24:10Now, what's the score, everybody?
0:24:10 > 0:24:12Did you get this?
0:24:12 > 0:24:16It's one each. I think it's a fair fury divide between us.
0:24:16 > 0:24:18Thank you very much indeed.
0:24:25 > 0:24:31So look, let's just look at the wreckage in here.
0:24:31 > 0:24:35So this got hit, but actually, this is paper and survived. It's all right, isn't it?
0:24:35 > 0:24:39And this metal plate got a bit dented but survived.
0:24:39 > 0:24:42So they seem good candidates for strong materials.
0:24:42 > 0:24:47This cup bit the dust, big time.
0:24:48 > 0:24:52- Porcelain cup, clearly a weak material. Wouldn't you agree?- Yes.
0:24:52 > 0:24:58Oh, you would, would you? You've fallen into my trap, ha-ha!
0:24:58 > 0:25:00All right, is it weak? Let's see.
0:25:00 > 0:25:03I've got a replica cup here.
0:25:03 > 0:25:05I want to show you how thin this is.
0:25:05 > 0:25:08You know how thin they are, but I'm just going to show you.
0:25:08 > 0:25:11Porcelain cups are fine bone china. You can actually shine lights through.
0:25:11 > 0:25:14Look at that. It's that thin.
0:25:14 > 0:25:17We're saying this is weak. But is it?
0:25:17 > 0:25:20I'm now going to do something which you shouldn't do at home.
0:25:20 > 0:25:25In fact, you shouldn't do any of this at home. Will you promise?
0:25:25 > 0:25:30I'm going to stand on this cup and see if it really is so weak. I'm pretty hefty.
0:25:30 > 0:25:33I didn't get on the scales earlier cos I was a bit embarrassed.
0:25:33 > 0:25:37But you see, I've got a lot of weight, gravity's pulling me down,
0:25:37 > 0:25:41all of my weight is going on the cup. No problem at all.
0:25:45 > 0:25:49So it seemed quite strong there, didn't it?
0:25:49 > 0:25:54I know what you're thinking. You're thinking, "They've got a dummy cup.
0:25:54 > 0:25:56"This is a super-strong cup and that was a weak cup."
0:25:56 > 0:26:02So just to prove to you that's not the case, and because I can...
0:26:02 > 0:26:05So the cup was pretty strong when I stood on it.
0:26:05 > 0:26:08But is it going to be able to survive this?
0:26:10 > 0:26:13No. Phew!
0:26:19 > 0:26:25So what's clear from any tantrum you've ever had, and this test here,
0:26:25 > 0:26:30is that there are different kinds of strength of materials.
0:26:30 > 0:26:33You've got a strength here which is about impact strength, and some
0:26:33 > 0:26:37things are great under impact and they're terrible under other things.
0:26:37 > 0:26:41So paper was good under impact, but if I put a paper cup down here, it would crush. On the other hand,
0:26:41 > 0:26:47the ceramic cup was terrible under impact and is fantastic under the compressive forces of me.
0:26:47 > 0:26:54So when we think about building a building out of materials, what we really need to think about is
0:26:54 > 0:27:00which type of strength we want, and in the case of a building, we want more like the compressive strength.
0:27:00 > 0:27:04So we have to make sure we're picking materials with high compressive strengths.
0:27:04 > 0:27:08What do I mean by ceramics and that kind of thing?
0:27:08 > 0:27:13A ceramic is a tiny... We saw it with the porcelain cup, it's tiny little crystals inside there.
0:27:13 > 0:27:15They're the same sort of crystals in jewellery.
0:27:15 > 0:27:18They're like rubies and sapphires and all these
0:27:18 > 0:27:23kind of aluminium oxide, silicon oxide, and they're tiny little crystals all bunched together.
0:27:23 > 0:27:27That cup seemed like a really good material to build a building out of.
0:27:27 > 0:27:31So you're thinking, "Why don't we have enormous buildings made out of cups?" Well, we do.
0:27:31 > 0:27:38Ceramics, that material, that class of material, is the same material as bricks, and it's the same material
0:27:38 > 0:27:46as stones and rocks and all these kinds of materials. But I want to show you an even better material.
0:27:55 > 0:27:59And this is it. Concrete. Absolutely fantastic material.
0:27:59 > 0:28:06This is such an amazing material, and we all just take it for granted, I think because it looks so sort
0:28:06 > 0:28:12of grey and dull, and so we think it must be grey and dull if it looks grey and dull. But it isn't.
0:28:12 > 0:28:16It's the stuff of absolute fantasmo. Is that a word?
0:28:16 > 0:28:22Anyway, I've said it. Look. Inside here is cement and gravel, and if
0:28:22 > 0:28:29you set this, you can pour it, you can shift it up 200 metres in the air,
0:28:29 > 0:28:32pump it up through huge pumps.
0:28:32 > 0:28:34That's how they make really tall buildings.
0:28:34 > 0:28:38They pump it up. So it behaves like a liquid, even though it's sort of a gravel aggregate.
0:28:38 > 0:28:40Then when it gets there, it'll set.
0:28:40 > 0:28:48It's not, as you might think, drying out. Actually, a chemical reaction is happening inside it.
0:28:48 > 0:28:51Let me show you. This is what's happening.
0:28:51 > 0:28:56Little crystals are growing inside the concrete. This is a ceramic.
0:28:56 > 0:29:01It's incredibly good compressive strength.
0:29:01 > 0:29:06What happens is that you've got this, basically a liquid rock which you can pump anywhere, you
0:29:06 > 0:29:10can pour anywhere, you can bring on, and then you can make these enormous
0:29:10 > 0:29:14buildings, and then when they set they have huge compressive strength.
0:29:14 > 0:29:17So this is a fantastic material.
0:29:17 > 0:29:20In fact, it seems we've kind of come to a material
0:29:20 > 0:29:23we need to make big buildings that build us off the planet.
0:29:23 > 0:29:29We need rock, basically - ceramic. It can be concrete or it can be stone, but this is the way, surely,
0:29:29 > 0:29:34this is the way to build huge buildings.
0:29:34 > 0:29:36Well, it's no news. You know it.
0:29:36 > 0:29:39We've been doing it for 5,000 years.
0:29:39 > 0:29:42Let me show you. It's getting a bit hot here.
0:29:47 > 0:29:50Yes, it's good to get some winter sun, don't you think?
0:29:50 > 0:29:55Look, I'm by the pyramids in Egypt, and these buildings have been built
0:29:55 > 0:29:59out of stone and they really show exactly what I'm talking about.
0:29:59 > 0:30:05They have lasted for 5,000 years, there's enormous compressive stresses at the bottom and they've
0:30:05 > 0:30:08been there for 5,000 years and this rock has not given up.
0:30:08 > 0:30:10Incredible down here.
0:30:10 > 0:30:16So, surely this is the right, both material and structure
0:30:16 > 0:30:19to start building ourselves off the planet.
0:30:19 > 0:30:24So, let's think about this. If I get a map out of central London...
0:30:24 > 0:30:27This is to scale.
0:30:29 > 0:30:31We are... We are...
0:30:31 > 0:30:34That is a very strange material.
0:30:34 > 0:30:39Hm! Anyway, sorry. We are...here.
0:30:39 > 0:30:43Albemarle Street. This is the RI to scale.
0:30:43 > 0:30:48It has a little hole in the roof just like this one has.
0:30:48 > 0:30:54OK? So, let's try and build the tallest building in the world but
0:30:54 > 0:30:59out of concrete, and let's do it in a pyramid structure because...
0:30:59 > 0:31:05Where are we going to put it? There seems to be a lot of space here.
0:31:05 > 0:31:08There's Green Park, there's St James's Park and there's
0:31:08 > 0:31:12this thing called Buckingham Palace Gardens that seems to be unoccupied.
0:31:12 > 0:31:17That's amazing, isn't it? That seems like a very likely spot.
0:31:17 > 0:31:19Yeah, let's do it.
0:31:19 > 0:31:22Let's have a go at this.
0:31:22 > 0:31:26We'll have to ask the Queen. That's the first thing we'll have to do.
0:31:26 > 0:31:29I think she'll be upset at losing her palace.
0:31:29 > 0:31:33She's got a few palaces but is pretty much attached to this one, I'm sure.
0:31:33 > 0:31:39So, we have to offer her space in this new building, that's what I'm thinking.
0:31:39 > 0:31:46Of course, we seem to have wiped out half of Mayfair here and Belgravia and that kind of thing.
0:31:46 > 0:31:49I guess that is the problem, isn't it?
0:31:49 > 0:31:55Pyramids are great, they last for a long time, they can cope with the stress, that's all fantastic.
0:31:55 > 0:31:57We have our structural head right on.
0:31:57 > 0:32:02Basically, this is to scale now so this would now be the tallest building in the world, a pyramid
0:32:02 > 0:32:07in the middle of London, which would be fantastic. It would be very impressive!
0:32:07 > 0:32:13If you think about it, if you try to build it even higher, say twice as high, so we are up there now.
0:32:13 > 0:32:17Think how big the footprint would have to be.
0:32:17 > 0:32:22It would have to take over the whole of central London, and at today's
0:32:22 > 0:32:27house prices, that would just be a mammoth planning task, wouldn't it?
0:32:27 > 0:32:32That would only get you so far and even then, how high would we really get?
0:32:32 > 0:32:39So, that's a real problem with pyramids. The plan area at the bottom that it takes up.
0:32:39 > 0:32:45There's another problem with pyramids. This is a picture of Mount Everest here.
0:32:45 > 0:32:47Mountains are essentially pyramids, aren't they?
0:32:47 > 0:32:50They're peaked at the top and they have a wide base.
0:32:50 > 0:32:55We can study them. Mount Everest is 10 times bigger
0:32:55 > 0:33:00than this pyramid here, if this was the highest building in the world - 0.8 kilometres.
0:33:00 > 0:33:01That's about eight kilometres high.
0:33:01 > 0:33:09Nature builds mountains itself, so it builds pyramids, and they don't get bigger and bigger and bigger.
0:33:09 > 0:33:12They sort of stay rather small.
0:33:12 > 0:33:14Why is that? Let's have a look because that is odd.
0:33:14 > 0:33:18You would have thought the geological processes in the Earth
0:33:18 > 0:33:23would allow us to get much bigger mountains than that. But here is the problem.
0:33:23 > 0:33:28This pyramid and that mountain are heavy - they are big objects.
0:33:28 > 0:33:32That mountain is two or three trillion tonnes.
0:33:32 > 0:33:37So, when it sits on the Earth's crust, and this, in case you were
0:33:37 > 0:33:43about to ask and I'm sure you were, is a model of the Earth's crust. And then underneath, the mantle.
0:33:43 > 0:33:50It is hot so we have the crust and the mantle here and it is hot rock, it is solid rock, but it is hot.
0:33:50 > 0:33:58Over millions of years, a trillion tonnes of mountain sits on that hot rock and this is what happens.
0:33:58 > 0:34:00It starts to sink. Why?
0:34:00 > 0:34:06Why does solid rock behave like a liquid and let things sink in it?
0:34:06 > 0:34:11That doesn't seem right but it turns out that, over millions of years,
0:34:11 > 0:34:14if it is hot enough - and it is hot enough -
0:34:14 > 0:34:18it flows like a liquid. The process of mountain building
0:34:18 > 0:34:24on this planet is, things pushing stuff up - a geological process making mountains - and them sinking
0:34:24 > 0:34:30back in, and the balance of those two forces determines the height of the mountains on this planet.
0:34:30 > 0:34:32You would think, hold on a minute.
0:34:32 > 0:34:36Surely you could get some enormous eruptions and get much bigger
0:34:36 > 0:34:40mountains like this one, which is three times the size of Everest.
0:34:40 > 0:34:43Three times the size of my model of Everest!
0:34:43 > 0:34:46Let us think what would happen then.
0:34:46 > 0:34:51It is much more than three times the weight, as you will know if
0:34:51 > 0:34:54you listened to lecture one, and look at that.
0:34:54 > 0:34:58It is sinking down and down, so you have much more mass being
0:34:58 > 0:35:04pulled down by gravity and it keeps going down and it keeps going down.
0:35:04 > 0:35:09The buoyancy forces, opposing these gravitational forces, mean this
0:35:09 > 0:35:15has to sit much further down then you would expect and this will keep going down.
0:35:15 > 0:35:19So, you can't just keep building bigger and bigger mountains and
0:35:19 > 0:35:26hope to have for them to stay around because the rock behaves like a liquid and they sink.
0:35:26 > 0:35:31You would think, "OK, why can't we do it on another planet with a lower
0:35:31 > 0:35:34"gravitational field or strength, like Mars?"
0:35:34 > 0:35:37Good question. And there it is.
0:35:37 > 0:35:42Olympus Mons on Mars is three times taller than Everest so it is
0:35:42 > 0:35:46bigger on Mars but it has a lower gravitational field.
0:35:46 > 0:35:52Clearly, this balance of forces is correct but it is still just a pimple on the surface of Mars.
0:35:52 > 0:36:00So, we can't build our way off the planet by building with big, heavy stuff.
0:36:00 > 0:36:06We need a material that is strong and light. So something that has a high strength-to-weight ratio.
0:36:06 > 0:36:09Let's think this through. I'm going to need a volunteer to help me.
0:36:11 > 0:36:15Who? Er... Yes.
0:36:15 > 0:36:19You, Sir, on the end.
0:36:19 > 0:36:22Hello. What is your name?
0:36:22 > 0:36:23- William.- OK, William.
0:36:23 > 0:36:26I've got something to show you here.
0:36:26 > 0:36:32So, we want something strong and light. I've got two materials here and they are both strong
0:36:32 > 0:36:37but we want to work out which one is stronger and lighter so it is a bit of a calculation.
0:36:37 > 0:36:40A steel bar, there we go.
0:36:40 > 0:36:45I want you to try and break it, bend it so you can't bend it any more.
0:36:45 > 0:36:48Oh, that's cheating but fair enough.
0:36:48 > 0:36:49- It is pretty strong, isn't it?- Yeah.
0:36:49 > 0:36:52No chance, right? What about this?
0:36:52 > 0:36:58This is another material that is very strong. It is called a carbon fibre composite. Try and bend that.
0:37:01 > 0:37:03Yeah. It's different, isn't it?
0:37:03 > 0:37:09- Yeah.- Which one of them has the best strength-to-weight ratio?
0:37:09 > 0:37:12- I would assume it would be this one. - Oh! I like your...
0:37:12 > 0:37:16But how can you tell because it doesn't seem like a fair test because did they weigh the same?
0:37:16 > 0:37:22- Not really.- No and in order to work that out, you would have to work out how much you were tensing it.
0:37:22 > 0:37:25So, what you'd like to see, wouldn't you...
0:37:25 > 0:37:27- Yeah.- ..is the same weight objects?
0:37:27 > 0:37:32So a piece of steel the same weight as that. That would be much easier?
0:37:32 > 0:37:35- Yeah.- Good thinking. So let's get something the same weight and let's
0:37:35 > 0:37:39weigh it, in case people think it's not the same weight.
0:37:39 > 0:37:40So here's the steel.
0:37:40 > 0:37:43That is 145 grams. All right.
0:37:43 > 0:37:46Now try and bend that. Go! Go!
0:37:46 > 0:37:51You can make noises as well if you want. I do.
0:37:51 > 0:37:58All right. If this one is worth 145 grams or thereabouts, we will then try and test that one again.
0:37:59 > 0:38:01This one is 145 grams.
0:38:01 > 0:38:05The same weight. Now bend this one.
0:38:05 > 0:38:09No chance. Suddenly, your original assumption about
0:38:09 > 0:38:12this one being the best strength per weight is absolutely correct.
0:38:12 > 0:38:15- Yeah.- Genius! Thank you very much.
0:38:15 > 0:38:17Fantastic!
0:38:17 > 0:38:21So, carbon composites are amazing.
0:38:21 > 0:38:27They are strong but light and these are revolutionising people's lives.
0:38:27 > 0:38:28Have a look at this.
0:38:29 > 0:38:35'It's another golden route to the line for British cycling.
0:38:35 > 0:38:37'The latest star is Jody Cundy.'
0:38:37 > 0:38:40Jody Cundy, come on! Here he comes!
0:38:40 > 0:38:44APPLAUSE
0:38:49 > 0:38:52Jody, tell us about your credentials.
0:38:52 > 0:38:56Well, I'm a double world champion, a multiple world record holder and
0:38:56 > 0:39:01double Paralympic champion in track cycling, and that was me winning in Beijing.
0:39:01 > 0:39:05- Wow! - APPLAUSE
0:39:06 > 0:39:12How much of it is you and how much of it is this marvellous material that your bike is made out of?
0:39:12 > 0:39:15Well, I like to think a lot of it is me making the bike go fast
0:39:15 > 0:39:19but the carbon fibre we have in the bikes really helps us go fast.
0:39:19 > 0:39:22They are shaped aerodynamically so we cut through the air.
0:39:22 > 0:39:25Even my leg is made of carbon fibre to cut through the air.
0:39:25 > 0:39:30- Wow!- The frame is made of carbon, the wheels are made of carbon, the
0:39:30 > 0:39:33handlebars are made of carbon and the seat post.
0:39:33 > 0:39:37Pretty much everything on the bike is carbon and it's basically there so
0:39:37 > 0:39:42- we transfer all the power we have in our legs to make the back wheel go so we go forward.- That's incredible.
0:39:42 > 0:39:44Your leg is actually the cycling leg?
0:39:44 > 0:39:50That's right. It's completely useless for walking in but it has a cycling cleat on the bottom just like any
0:39:50 > 0:39:54- other shoe and it clips into my pedals.- It's amazing, isn't it?
0:39:54 > 0:39:56- Can I just see how light...? - Yes, sure.
0:39:56 > 0:40:00I want to see if I can lift it up with one finger.
0:40:00 > 0:40:02APPLAUSE
0:40:05 > 0:40:08This is an absolute thing of beauty, isn't it?
0:40:08 > 0:40:11- Thank you so much for coming in. - Not a problem.
0:40:11 > 0:40:13- It is a real privilege to meet you. - Thank you.
0:40:13 > 0:40:15APPLAUSE
0:40:21 > 0:40:28It's not just in Olympic sports or extreme sports but it is also everyday life.
0:40:28 > 0:40:32This is a material that will affect every one of you.
0:40:32 > 0:40:39I want to show you the latest aircraft from Airbus, the A380.
0:40:39 > 0:40:42This is a double-decker plane.
0:40:42 > 0:40:4720 per cent of this is carbon-fibre composite and this is only going to increase.
0:40:47 > 0:40:53As the years go on, I'm pretty confident that in 10 years' time, 70 or 80 per cent of aircraft will
0:40:53 > 0:40:59be carbon-fibre or other composites. We've brought some in from an actual A380.
0:40:59 > 0:41:03This is part of the underwing component. We've got two bits of it here.
0:41:03 > 0:41:08It is carbon fibres, so a bit like the graphite in pencils but made into a fibre
0:41:08 > 0:41:16and then it is interwoven with a resin - a plastic - and that is why it is called a composite.
0:41:16 > 0:41:21It is part fibre - carbon fibre - and part resin and this resin,
0:41:21 > 0:41:27this plastic is the sort of thing you get with Araldite. Almost like a glue.
0:41:27 > 0:41:31On their own they are not so useful but put them together
0:41:31 > 0:41:35and you get this marvellously strong material.
0:41:35 > 0:41:40I want to give you an experience of how strong these materials are.
0:41:40 > 0:41:46I need a volunteer. Yes, you on the end with the Christmas hat.
0:41:46 > 0:41:49APPLAUSE
0:41:51 > 0:41:53What's your name?
0:41:53 > 0:41:56- Katie.- Katie, are you strong?
0:41:56 > 0:41:59- Er, yeah...?- OK.
0:41:59 > 0:42:03- Have you got a bad back?- No.- Good.
0:42:03 > 0:42:08OK. I just want you to lift this up and I'll tell you what to do later.
0:42:08 > 0:42:10Do you think you'll be able to lift that up?
0:42:10 > 0:42:12- Yeah.- Oh!
0:42:12 > 0:42:14Actually, it's quite light, isn't it?
0:42:14 > 0:42:18- Yeah.- You could look a little bit more surprised if you like!
0:42:18 > 0:42:21No. Don't worry. Are you surprised how light that is?
0:42:21 > 0:42:24- Yeah.- It's incredible.
0:42:24 > 0:42:28That's an enormous piece of stuff and it's very light.
0:42:28 > 0:42:32In fact, it's so light... Can you continue to hold it?
0:42:32 > 0:42:36Are you getting strain? No, it's so light.
0:42:36 > 0:42:38I can lift this up with one hand.
0:42:38 > 0:42:43It's the size of a wardrobe and yet... All right! Come on, guys!
0:42:43 > 0:42:45- APPLAUSE - OK. Thank you very much.
0:42:45 > 0:42:53- I wasn't going to get you to smash it because there has been enough smashing, hasn't there?- Yeah.
0:42:53 > 0:42:54Thank you very much.
0:42:58 > 0:43:02So the key to this material is its strength-to-weight ratio.
0:43:02 > 0:43:04It's a fantastic material for that.
0:43:04 > 0:43:08So, could we use these materials to build ourselves off the planet?
0:43:08 > 0:43:14That is the question. And make things that are really, really tall?
0:43:14 > 0:43:18Let us defeat gravity once and for all with these light materials.
0:43:18 > 0:43:26Earlier, here, we were looking at the Earth and we worked out that we'd have to get 36,000 kilometres
0:43:26 > 0:43:31over here before we could really get out of the grips of gravity.
0:43:31 > 0:43:37What we want to try and do is build a building 36,000 kilometres high.
0:43:37 > 0:43:42We'd already worked out we'd need something with high strength-to-weight ratio.
0:43:42 > 0:43:47So, let's see how all the materials we have so far come across do on that rating. Oh...!
0:43:47 > 0:43:52Have you still got your common sense turned on?
0:43:52 > 0:43:59That is a very silly material. All right. This is a scale model of
0:43:59 > 0:44:02the Burj Khalifa, the tallest building in the world,
0:44:02 > 0:44:07scaled down, so it is 0.8 kilometres high - half-a-mile high.
0:44:07 > 0:44:13If we were to build a building out of steel, pure, solid steel and keep
0:44:13 > 0:44:19going up, we would get up to 4 kilometres high.
0:44:19 > 0:44:24So, we could build a building 4 kilometres high no problem at all.
0:44:24 > 0:44:29If we use concrete, we would get up to 4.7 kilometres high.
0:44:29 > 0:44:33That is incredible. It is insane!
0:44:33 > 0:44:38It really makes the current buildings we live in look puny.
0:44:38 > 0:44:44Actually, modern buildings are often built with a combination of steel and concrete so if you do
0:44:44 > 0:44:49the calculations, you could probably get up to 5 kilometres with a combination of these two materials.
0:44:49 > 0:44:535 kilometres high for the materials that we know about.
0:44:53 > 0:44:56What about carbon fibre?
0:44:56 > 0:45:02What about this fantastic material with strength-to-weight ratio that is much better? Let's see.
0:45:02 > 0:45:04It's actually extremely high.
0:45:04 > 0:45:08It's really impressively high.
0:45:08 > 0:45:16We actually have to go higher and higher... Higher than the steel, higher than the concrete,
0:45:16 > 0:45:20higher than the combination of steel and concrete
0:45:20 > 0:45:24and even higher and higher and higher to 7 kilometres.
0:45:24 > 0:45:29We could build a building 7 kilometres high with carbon-fibre composite.
0:45:29 > 0:45:35A material it is really light but strong, and the advantage is there isn't this huge mass bearing down
0:45:35 > 0:45:42on it because it is so light and yet it is really strong so it can withstand a lot of its own weight.
0:45:42 > 0:45:47The other brilliant thing is the view is fantastic up here. Amazing!
0:45:55 > 0:45:597 kilometres is really impressive. Let's say we could really make some advances.
0:45:59 > 0:46:04We could get to maybe 10 kilometres if we bettered the design.
0:46:04 > 0:46:09Maybe we could get to 100 kilometres in the next century or so. It still wouldn't be anywhere near
0:46:09 > 0:46:1336,000 kilometres which we would need to build ourselves off the planet
0:46:13 > 0:46:16and that is what we want to do, right?
0:46:16 > 0:46:21That seems like a really great thing to do. Yet, hm...
0:46:21 > 0:46:24So, is there another way to think about this problem?
0:46:24 > 0:46:27ALL: Behind you!
0:46:27 > 0:46:29Crikey! Well!
0:46:29 > 0:46:31But, yeah, you're right.
0:46:31 > 0:46:36I can see your point you're trying to make with that, because spiders
0:46:36 > 0:46:41don't build up, they've got more sense than that. They build down.
0:46:41 > 0:46:47They go up to the top and then they come down on a little fibre.
0:46:47 > 0:46:49So, that gives me an idea.
0:46:49 > 0:46:54Why can't we do the same thing with this problem?
0:46:54 > 0:47:00Just turn the whole thing upside down. Let's not build up, let's build down.
0:47:00 > 0:47:04Or, not build, let's send a cable down.
0:47:04 > 0:47:10If I am here orbiting the Earth as a satellite, OK?
0:47:10 > 0:47:17And then I get a cable and I send it down to Earth like this,
0:47:17 > 0:47:23and I just keep sending it down and I keep going and
0:47:23 > 0:47:30I keep going and I keep going for 36,000 kilometres...
0:47:30 > 0:47:36And then when we get to the bottom, we tie it off.
0:47:36 > 0:47:41I know that sounds ridiculous but just go with me on this one.
0:47:41 > 0:47:48Now we've got a cable from a satellite orbiting the Earth to the Earth's surface.
0:47:48 > 0:47:56Now, attach an elevator to that and what do you have but a space elevator?
0:47:56 > 0:48:01And we could just get into it and go up to space.
0:48:01 > 0:48:05How fantastic would that be?
0:48:05 > 0:48:07It would be brilliant.
0:48:07 > 0:48:12The thing is, of course, when you're paying
0:48:12 > 0:48:16a cable down, there's huge gravitational forces
0:48:16 > 0:48:19pulling it to Earth because of the enormous weight of the cable.
0:48:19 > 0:48:24Again, you'd need something with very high strength-to-weight ratio, wouldn't you?
0:48:24 > 0:48:27How strong does it have to be? If you do the calculations,
0:48:27 > 0:48:31it turns out that you need something that would be so strong
0:48:31 > 0:48:37that if you had a 1mm-thick fibre - something a bit like a thread - it would have
0:48:37 > 0:48:45to suspend the whole audience, which is 20 tonnes. That seems like quite a big task.
0:48:45 > 0:48:51Well, I've been thinking about this, we do have fibres that are very strong, don't we?
0:48:51 > 0:48:55As a scientist, it is a very competitive field and often
0:48:55 > 0:49:00I get the feeling that people want to take a pot-shot at me.
0:49:00 > 0:49:05So, like a lot of other scientists worried about this, I have a body double.
0:49:05 > 0:49:11Occasionally, I send the body double to conferences instead of me, just to see what happens.
0:49:11 > 0:49:14The other week, this is what happened.
0:49:20 > 0:49:22I knew it!
0:49:22 > 0:49:26I knew they were after me.
0:49:26 > 0:49:29Luckily, they mistook my body double for me and here he is. He survived.
0:49:29 > 0:49:31APPLAUSE
0:49:33 > 0:49:41Now, the reason he survived - and it is not really him because he is plastic, I know that!
0:49:41 > 0:49:45But he has one of my shirts on and I didn't want him to get that hurt
0:49:45 > 0:49:47so I put on a Kevlar bulletproof vest.
0:49:47 > 0:49:51You can see that the bullets went in here
0:49:51 > 0:49:56and in through here, but they did not make it through the Kevlar.
0:49:56 > 0:49:59These bits on the outside are sort of nylon outer layers
0:49:59 > 0:50:05and inside is the Kevlar. It is an extremely strong fibre.
0:50:05 > 0:50:07I will show you where it is.
0:50:07 > 0:50:08That is Kevlar.
0:50:08 > 0:50:12It is an extremely fine weave
0:50:12 > 0:50:14and extremely strong fibre.
0:50:17 > 0:50:18So what is Kevlar?
0:50:18 > 0:50:25It is a set of molecules that have been assembled molecule by molecule at the atomic scale.
0:50:25 > 0:50:31Its strength really is very close to the atomic strength of those molecules together.
0:50:31 > 0:50:37So, you are breaking atomic bonds to break this material and that means that it is extremely strong.
0:50:39 > 0:50:43Is it strong enough, though, to build the cable for the space elevator?
0:50:43 > 0:50:45It turns out to be not.
0:50:45 > 0:50:51It would only support a couple of people with a thickness of that fibre.
0:50:51 > 0:50:55Although Kevlar's fantastic for saving lives,
0:50:55 > 0:51:00and it really is the material of choice, it isn't good enough for what we want it to do.
0:51:00 > 0:51:05That is a bit of a problem, but recently there have been
0:51:05 > 0:51:08some material science discoveries that have kind of given us hope.
0:51:08 > 0:51:13It turns out that the ingredients for this material that has given us hope,
0:51:13 > 0:51:16you've experienced yourself at every birthday you've ever had.
0:51:16 > 0:51:21I want to ask if there is anyone here whose birthday is this week?
0:51:21 > 0:51:24It is your birthday this week? All right.
0:51:24 > 0:51:25Do you mind coming down?
0:51:28 > 0:51:30Hello. What is your name?
0:51:30 > 0:51:35- Catherine.- Catherine, and it is your birthday this week. What do you have on your birthday? A cake!
0:51:35 > 0:51:39Here we go! A birthday cake for you for next Monday.
0:51:40 > 0:51:46Now, would you believe that the ingredients for a great new material are here?
0:51:46 > 0:51:48Where are they, though?
0:51:48 > 0:51:52Are they in the cake, the icing, the ribbon, the wax?
0:51:52 > 0:51:54Well, let me take a sample of it.
0:51:57 > 0:52:01And now you can blow out the candles if you like.
0:52:05 > 0:52:07Happy birthday!
0:52:10 > 0:52:16So, on this glass slide I collected some of the ingredients for this material.
0:52:16 > 0:52:17It turns out that,
0:52:17 > 0:52:23until 10 or 20 years ago, we thought that there were only two forms of carbon -
0:52:23 > 0:52:26diamond, which is superhard and translucent
0:52:26 > 0:52:30and there was graphite which we use in pencils. We thought that was it.
0:52:30 > 0:52:37Then people started looking around and realised that carbon can arrange itself in other amazing ways.
0:52:37 > 0:52:44One of them we found in the soot of candles, which is an incredible place to find it.
0:52:44 > 0:52:49In here are molecules that look like this.
0:52:49 > 0:52:52They are called buckyballs and they are a different way
0:52:52 > 0:52:57of arranging carbon and they are really beautiful things.
0:52:57 > 0:53:01And if you use these
0:53:01 > 0:53:06and you re-combine them, you can make things like this and these are called carbon nanotubes.
0:53:06 > 0:53:10This is a fantastically strong
0:53:10 > 0:53:16and light material. The reason is this. It's mostly carbon. Well, it's only carbon.
0:53:16 > 0:53:22Carbon is a really light element, one of the lightest elements in the periodic table so your ingredients
0:53:22 > 0:53:25are really light. The bonds between them are really strong.
0:53:25 > 0:53:30It is a really strong structure and in the middle, there is nothing.
0:53:30 > 0:53:33So there is even less density. These things...
0:53:33 > 0:53:37You all know what it's like when you have a piece of paper and it waves about
0:53:37 > 0:53:41and you wrap it into a column and suddenly it is strong and stiff.
0:53:41 > 0:53:44You've got the same thing going on here.
0:53:44 > 0:53:48At a molecular level, this thing is as an extraordinarily strong structure.
0:53:48 > 0:53:52In fact, it is theoretically, when you do the quantum mechanics calculations,
0:53:52 > 0:53:55you find this has the strength we need
0:53:55 > 0:53:57to make the space elevator cable.
0:53:57 > 0:54:01But, of course, they are tiny things. Let me show you how small they are.
0:54:01 > 0:54:05I can't really show you how small they are because all I can show you is a jar of them.
0:54:05 > 0:54:09They are individual little nanoscales.
0:54:09 > 0:54:14This is at the scale of one billionth so they are a billion times smaller than this.
0:54:14 > 0:54:17So, the big challenge is then
0:54:17 > 0:54:22to join these up into one long thread and that is really difficult.
0:54:22 > 0:54:26Then, to get those threads into a twine and then into a cable.
0:54:26 > 0:54:30If you are familiar with suspension bridges, you've got small bits of steel
0:54:30 > 0:54:34into a twine, bigger bits of steel, bigger, bigger, bigger.
0:54:34 > 0:54:36All wrapped around. So that is a cable.
0:54:36 > 0:54:42Let me tell you how far materials scientists have got. They can make nanotubes.
0:54:42 > 0:54:49Here are some of the first ever in the world examples of threads made with nanotubes.
0:54:49 > 0:54:51This really is an amazing sample.
0:54:51 > 0:54:54This was made in the Windle lab in Cambridge.
0:54:54 > 0:55:00It really is these joined together in a thread. Let me show you under the microscope.
0:55:00 > 0:55:07It is an incredibly exciting moment for everyone because we had all been hoping this material could be made
0:55:07 > 0:55:11and this really is the jump between theory - the theoretical material science -
0:55:11 > 0:55:14to the practical material science and then to the engineering.
0:55:14 > 0:55:18At the moment, it is not there yet, but it is going to happen.
0:55:18 > 0:55:22People are going to get better and better at making this into that material.
0:55:22 > 0:55:28When they do, we are going to have a material that can make a space elevator.
0:55:28 > 0:55:31If we've got the materials that we can make this cable out of,
0:55:31 > 0:55:34and that was the big challenge, the rest looks pretty straight forward.
0:55:34 > 0:55:37Let me talk you through what we would have to do.
0:55:37 > 0:55:41We'd have to get up into space, get a satellite that was orbiting the Earth,
0:55:41 > 0:55:44geostationary orbit 36,000 kilometres.
0:55:44 > 0:55:47Then we have to work out a way of making the material up here
0:55:47 > 0:55:51because we wouldn't want to get it up here all the time.
0:55:51 > 0:55:56So we make it up here and we start paying out this cable down, 36,000 kilometres down.
0:55:56 > 0:55:59Then we tether it to the Earth.
0:55:59 > 0:56:01You can see where it hits is in the ocean.
0:56:01 > 0:56:05We want it on the equator and we want it in the ocean because we want
0:56:05 > 0:56:10to tether it to a boat so that if there is any movement, it is taken up by the viscosity of the sea.
0:56:11 > 0:56:13Then... Of course, you are all thinking this.
0:56:13 > 0:56:17All of it would collapse under its own gravitational weight back to the Earth.
0:56:17 > 0:56:22Good thought. What we would have to do is kind of have a counterweight.
0:56:22 > 0:56:26So we would send a piece of material this side which exactly
0:56:26 > 0:56:29has the counterweight of the force going in so the whole thing is in balance.
0:56:29 > 0:56:35Now what happens is that you decide you want to go to space. Any of you.
0:56:35 > 0:56:41So, you get a boat to the docking station and you get on the elevator
0:56:41 > 0:56:47and you come up 36,000 kilometres and you hit and suddenly you are weightless.
0:56:47 > 0:56:50APPLAUSE
0:56:54 > 0:56:56How fantastic would that be?
0:56:56 > 0:57:01Our parents' generation went to the moon. They gave that as a present to us
0:57:01 > 0:57:04and it was an incredible achievement. We have got to live up to that.
0:57:04 > 0:57:11We have got to do something just as good and give something to the next generation and this, I think, is it.
0:57:11 > 0:57:14This is our challenge for our generation.
0:57:14 > 0:57:17This is what is left over for us to do.
0:57:17 > 0:57:21To make mass space transport via an elevator possible for everybody.
0:57:21 > 0:57:26So, let's do it! Come on, guys, let's just do it!
0:57:26 > 0:57:28Don't you think?
0:57:28 > 0:57:30ALL: YES!
0:57:43 > 0:57:48So, I hope you've enjoyed these lectures about scale and materials.
0:57:48 > 0:57:52We've seen that everything changes as you get smaller.
0:57:52 > 0:57:54Things get superstrong.
0:57:54 > 0:57:59You can survive enormous falls, you can engineer materials to be incredible.
0:57:59 > 0:58:02You can devise invisibility shields.
0:58:02 > 0:58:07And ants are superstrong when they are small and hamsters are superstrong because they are small
0:58:07 > 0:58:11and they can survive these enormous falls because of their size.
0:58:11 > 0:58:14But we get to live longer than them because we are large.
0:58:14 > 0:58:17So it all depends on how big you are.
0:58:17 > 0:58:23Size really does matter and I hope that you've enjoyed this tour
0:58:23 > 0:58:26through the scale of the universe and life.
0:58:26 > 0:58:28Thank you very much for listening.
0:58:28 > 0:58:30APPLAUSE
0:58:45 > 0:58:48Subtitles by Red Bee Media Ltd
0:58:48 > 0:58:51E-mail subtitling@bbc.co.uk