0:00:16 > 0:00:19CHEERING AND APPLAUSE
0:00:26 > 0:00:28Well...
0:00:28 > 0:00:29Hello, everybody. Hello.
0:00:29 > 0:00:31My name is Mark Miodownik,
0:00:31 > 0:00:35I'm a material scientist from King's College London.
0:00:35 > 0:00:37I'm going to talk you about stuff.
0:00:37 > 0:00:39You're all made of stuff.
0:00:39 > 0:00:42I'm made of stuff, this floor is made of stuff. It's wonderful stuff.
0:00:42 > 0:00:45You think you know something about stuff, don't you?
0:00:45 > 0:00:50I'm going to show you some strange stuff that perhaps you don't know so much about.
0:00:50 > 0:00:52The Royal Institution - such a civilised place!
0:00:52 > 0:00:55A cup of tea before I start my lecture, how wonderful.
0:00:55 > 0:00:57I need some sugar. Let's get some sugar stuff.
0:00:57 > 0:01:01Here it is. Put it in my tea...
0:01:01 > 0:01:04Now, look, even the cup is made of stuff.
0:01:04 > 0:01:06The spoon is made of stuff.
0:01:06 > 0:01:08Stir my cup...
0:01:08 > 0:01:14The thing about stuff is that sometimes it does things that you weren't really expecting...
0:01:16 > 0:01:21A spoon that melts in your tea. Not so useful, maybe, but still incredible, don't you think?
0:01:21 > 0:01:24Now...while we're on incredible,
0:01:24 > 0:01:27I've got a liquid here that's incredible.
0:01:27 > 0:01:32And before I show it to you, I want to ask you all a favour.
0:01:32 > 0:01:35Could you all turn off your common sense for this lecture?
0:01:35 > 0:01:40I need you just to turn it off. I know your mums and dads want you to have it on afterwards,
0:01:40 > 0:01:42but I'll be showing you things so strange, so odd,
0:01:42 > 0:01:47that it'll be a hindrance if you keep saying, "Oh, that doesn't make any sense."
0:01:47 > 0:01:53Turn off your common sense. Now, liquids and mobile phones, they don't really mix, do they?
0:01:53 > 0:01:58Anyone who's ever sat on the loo with their phone in the back pockets and heard a splosh knows this.
0:01:58 > 0:02:00So, you shouldn't do this, should you?
0:02:00 > 0:02:02Right?
0:02:02 > 0:02:04PHONE RINGS
0:02:04 > 0:02:08No problem at all if you've got a strange liquid called a fluorocarbon.
0:02:08 > 0:02:11This stuff doesn't hurt mobile phones at all.
0:02:11 > 0:02:14In fact, mobile phones love it. Still working, fine.
0:02:14 > 0:02:16Don't you think we should put this in all the loos?
0:02:16 > 0:02:21Don't you think? That would save us all a lot of bother.
0:02:21 > 0:02:25So, stuff really can just take you completely unawares.
0:02:25 > 0:02:29Here is a coffee cup set, sent to me by my aunt.
0:02:29 > 0:02:34I was using it for ages until I thought, there's something very odd about this.
0:02:34 > 0:02:37I took it into the lab and we did all sorts of tests on it.
0:02:37 > 0:02:41Nothing came up positive, until we used the Geiger counter on it.
0:02:41 > 0:02:44Now, a Geiger counter detects radioactivity.
0:02:44 > 0:02:45BLEEP
0:02:45 > 0:02:48Now, if I'm radioactive, this will click.
0:02:48 > 0:02:49Phew!
0:02:51 > 0:02:52CLICKING
0:02:52 > 0:02:56It's a very strange present from your aunt, don't you think?
0:02:56 > 0:03:00I've been checking all her presents from then on with a Geiger counter, I can tell you.
0:03:00 > 0:03:04So, how do we understand these strange properties of matter?
0:03:04 > 0:03:09And once we understand them, can we use them to make even more marvellous things?
0:03:09 > 0:03:12Well, in order to understand that, I need to take you on a journey,
0:03:12 > 0:03:16which is going to involve understanding about size.
0:03:16 > 0:03:22And... What does that mean? Well, we're sort of used to the three dimensions of space, aren't we?
0:03:22 > 0:03:25X, Y, Z, left, right, down, back, up.
0:03:25 > 0:03:30You sort of think, if I know where I am in those dimensions, surely I know everything?
0:03:30 > 0:03:32But it turns out not to be true.
0:03:32 > 0:03:36It turns out that even for a whale, or an ant, or a teacup,
0:03:36 > 0:03:41you need to know how big you are if you know how things are going to happen in the world.
0:03:41 > 0:03:46Let me take you on a journey. We're going to be dimension travellers in these lectures.
0:03:46 > 0:03:51I'm going to take you to the really big. I'm going to take you to skyscrapers.
0:03:51 > 0:03:57I'm going to show you that the forces that dominate up there is gravity.
0:03:57 > 0:04:01That's going to really make a big difference to huge things.
0:04:01 > 0:04:03Then, we're going to zoom into small things, atoms,
0:04:03 > 0:04:07and we'll see that different physics dominates down there.
0:04:07 > 0:04:10Quantum mechanics, very strange stuff goes on.
0:04:10 > 0:04:15And despite the fact that it's very small, there's a lot of space down there.
0:04:15 > 0:04:21How weird is that? The key point is going to be that at different scales, different physics dominates.
0:04:21 > 0:04:26So, even though I can stand on a tiny salt crystal,
0:04:26 > 0:04:30it's not gravity that keeping me stuck to it,
0:04:30 > 0:04:34it's the surface forces of this crystal plane.
0:04:34 > 0:04:36It's actually very sticky. Oh!
0:04:36 > 0:04:40In this lecture, what we are going to be doing is looking at animals,
0:04:40 > 0:04:43and how size affects animal behaviour.
0:04:43 > 0:04:46In particular, why it's very useful to be small.
0:04:46 > 0:04:50So, we're going to look at ants to see how they're super-strong.
0:04:50 > 0:04:55And to be honest, when you're shrunk down like this, super-scary!
0:04:55 > 0:04:59And then, we're going to look at the big things - elephants.
0:04:59 > 0:05:03Wonderful, huge creatures, amazing things.
0:05:03 > 0:05:06But it turns out they're not actually relatively very strong.
0:05:06 > 0:05:10And we're going to ask the question, can they really dance?
0:05:11 > 0:05:14So that's the journey we're going to take.
0:05:14 > 0:05:18Now, I've got a pet hamster...
0:05:18 > 0:05:24called Hamish. Has anyone here got a pet at all?
0:05:24 > 0:05:27Have any of you got pets? You have? Shout out their names.
0:05:27 > 0:05:29Cats? Dogs? What have you got?
0:05:29 > 0:05:32- SHOUTING - Dog? Crocodile?!
0:05:36 > 0:05:38OK, all right. Fantastic. Now...
0:05:41 > 0:05:45..I took my pet hamster on holiday with me.
0:05:45 > 0:05:48I hope you all take your pets on holiday with you. We went to Dubai.
0:05:48 > 0:05:54The reason we went to Dubai - it's very hot there, I wanted to get the sun, so did my hamster -
0:05:54 > 0:05:57is because we wanted to see the tallest building in the world.
0:05:57 > 0:06:00This is the Burj Khalifa, and it is huge.
0:06:00 > 0:06:05It's half a mile high and we went to the top, and this is what happens when you look down.
0:06:05 > 0:06:08It is very scary. Half a mile down.
0:06:08 > 0:06:14That's what it seems. I had my hamster and I said to my hamster, woah, that's a long way down.
0:06:14 > 0:06:17Tell you what, I'll race you to the bottom.
0:06:17 > 0:06:21You go this way, right, and I'll take the lift.
0:06:21 > 0:06:24The funny thing is, that he kind of was up for that.
0:06:24 > 0:06:26He was up for jumping.
0:06:26 > 0:06:30Now, that isn't a very tenable position for a hamster, is it?
0:06:30 > 0:06:31Jumping off a building...
0:06:31 > 0:06:35Or is it? Maybe he knows something that I don't.
0:06:35 > 0:06:41Now, if I fell from this height, I'd certainly die, but could Hamish survive?
0:06:41 > 0:06:45Does size matter when it comes to falling off buildings?
0:06:45 > 0:06:50We really should meet Hamish, don't you think, and see what he's got to say.
0:06:50 > 0:06:55Come and meet Hamish the hamster, and also his friend, the dog Sweep.
0:06:55 > 0:06:57Ah, here's Hamish.
0:06:57 > 0:07:00Hello, Hamish.
0:07:02 > 0:07:03And Sweep. What's your name?
0:07:03 > 0:07:06- Charlotta.- Charlotta, and you're...? - Alan.
0:07:06 > 0:07:09Alan, and you've got Sweep and Hamish. Ah, how's he doing?
0:07:09 > 0:07:11How sweet, they're both happy.
0:07:11 > 0:07:16Now, who thinks that Hamish could survive a drop off a tall building? Quite a lot of you.
0:07:16 > 0:07:21And who thinks they have no chance, Hamish has no chance of survival? Who thinks that?
0:07:21 > 0:07:26A few of you. OK, so we're undecided in this audience, aren't we? OK.
0:07:26 > 0:07:28And what about Sweep the dog?
0:07:28 > 0:07:31Who thinks Sweep the dog can survive a large fall off a building?
0:07:31 > 0:07:35- No one does.- I do!- Oh, you do! Fantastic! OK, love it.
0:07:35 > 0:07:39OK, great. So, how would we decide this?
0:07:39 > 0:07:41How can we decide if this is true?
0:07:41 > 0:07:43Well, let's do an experiment, right?
0:07:43 > 0:07:46You'll have noticed we've got this large box in this lecture theatre.
0:07:46 > 0:07:49This isn't as tall as a tall building, but it's pretty high.
0:07:49 > 0:07:57So, if we do an experiment dropping pets, we're going to surely find out the answer to this, aren't we?
0:07:57 > 0:08:01Now, of course we're not going to drop real pets. Did you think...?
0:08:01 > 0:08:03Come on!
0:08:03 > 0:08:07I really hope that no one at home either thinks about dropping pets.
0:08:07 > 0:08:09It's really cruel, we'd never do that. We'd never do that.
0:08:09 > 0:08:12We've got some crash-test pets here to take the place of these pets,
0:08:12 > 0:08:16and we're going to do the experiment with these crash-test pets.
0:08:16 > 0:08:19Later, we'll bring you two back on to review the results.
0:08:19 > 0:08:21Is that OK, Hamish? Yeah, you can watch.
0:08:21 > 0:08:26You go back and take your seat, and you too, Sweep, and we'll see what happens.
0:08:26 > 0:08:29All right, so, this is pretty exciting.
0:08:29 > 0:08:32This is Andy. Andy has rigged up this thing and it's a box.
0:08:32 > 0:08:36It's going to take these crash-test pets to the top of this lecture theatre.
0:08:36 > 0:08:38Now, what are these crash-test pets?
0:08:38 > 0:08:44They're balloons filled with jelly, which is ballistic jelly.
0:08:44 > 0:08:48It replicates the flesh of a...
0:08:48 > 0:08:53Well, a bit. All right. So, this is crash-test dog.
0:08:53 > 0:08:54He's ready, isn't he?
0:08:54 > 0:08:56And this is crash-test hamster.
0:08:56 > 0:09:00Oh, he's moving all over the place! They're a bit nervous, fair enough.
0:09:00 > 0:09:04They're going to have a bit of a jump. They're intrepid pets.
0:09:04 > 0:09:08Let's put crash-test hamster up and let's go for this.
0:09:08 > 0:09:12All right, up he goes. You'll notice that they're both the same shape, right?
0:09:12 > 0:09:15And they're both made of the same material.
0:09:15 > 0:09:17So this is a fair comparison.
0:09:17 > 0:09:19Sometimes they don't want to jump,
0:09:19 > 0:09:22they get nervous. You know what it's like at the top of a tall building.
0:09:22 > 0:09:28So, we've got this trap door. And I press this button and crash-test hamster has no choice but to drop.
0:09:28 > 0:09:31It's a bit of a James Bond trick, actually.
0:09:31 > 0:09:36OK, crash-test hamster. Let's do a countdown for him, shall we?
0:09:36 > 0:09:395, 4, 3,
0:09:39 > 0:09:412, 1...
0:09:42 > 0:09:46Woah! Let's hear it for the crash-test hamster.
0:09:46 > 0:09:49Yes!
0:09:52 > 0:09:58OK, so crash-test hamster has survived, as most of you thought.
0:09:58 > 0:10:01And now let's just have a look at him.
0:10:01 > 0:10:03How is he feeling? Yes, you're fine, well done.
0:10:03 > 0:10:05Good one. He's all right.
0:10:05 > 0:10:08Bring it on, he's saying. Taller, higher, bigger!
0:10:08 > 0:10:12Crash-test dog's looking a bit nervous now. His turn next.
0:10:12 > 0:10:16Crash-test dog, how are you feeling? Yes, all right, you're a bit quiet.
0:10:16 > 0:10:19Let's get crash-test dog in here.
0:10:21 > 0:10:24How's he feeling? All right.
0:10:24 > 0:10:25Crash-test dog, up he goes.
0:10:25 > 0:10:29I've got a little communication link with crash-test dog.
0:10:29 > 0:10:33Yes, I know, I know. You'll get a bone, yes, yes.
0:10:33 > 0:10:36All right. 5, 4, 3,
0:10:36 > 0:10:392, 1...
0:10:40 > 0:10:42Oh!
0:10:53 > 0:10:57I think we might need an ambulance... Oh...
0:11:02 > 0:11:04Yeah... I think...
0:11:04 > 0:11:09We're getting the ambulance. OK, fine. The jelly ambulance is coming.
0:11:09 > 0:11:12So crash-test dog is not looking too well from that fall.
0:11:12 > 0:11:17It turns out that essentially, as you guys thought, most of you,
0:11:17 > 0:11:21it does actually matter how big you are, whether you survive a fall.
0:11:21 > 0:11:24So, what's changed? We've got the same material.
0:11:24 > 0:11:27One of them isn't stronger than the other one.
0:11:27 > 0:11:31It's just jelly, and they're both made of jelly. So, what has changed?
0:11:31 > 0:11:33One is bigger than the other.
0:11:33 > 0:11:35What does bigger mean? Let's think about volume.
0:11:35 > 0:11:37It's a funny word isn't it, volume?
0:11:37 > 0:11:40You kind of think of it as liquids, and things you drink.
0:11:40 > 0:11:44But it actually just means how much space you're occupying.
0:11:44 > 0:11:47It is an odd thing. Let's just explore volume for a bit.
0:11:47 > 0:11:51I'm going to need a volunteer for this, OK?
0:11:51 > 0:11:53Yes, would you like to volunteer?
0:11:54 > 0:11:55Yes.
0:11:55 > 0:11:57APPLAUSE
0:11:57 > 0:11:58Hello. What's your name?
0:11:58 > 0:12:02- Annie.- Annie, do you want to come round here, Annie?
0:12:02 > 0:12:05Here we go. This looks like some weird game.
0:12:05 > 0:12:07It's sort of is, in a way. I hope you're up for this.
0:12:07 > 0:12:11Now, we've got once sphere here, which is empty.
0:12:11 > 0:12:16It's twice as big as these small spheres, which are full of water, coloured water.
0:12:16 > 0:12:19When I said it's twice as big, you didn't stop me there, did you?
0:12:19 > 0:12:24But you probably wanted to say, tell me more, what do you mean by bigger? Right? Good thinking.
0:12:24 > 0:12:26I'll answer that question. It's an excellent question.
0:12:26 > 0:12:29I'm talking about the width. So, the diameter.
0:12:29 > 0:12:31Let me just prove that to you.
0:12:31 > 0:12:35So, this is seven and a half in width,
0:12:35 > 0:12:37diameter. And this is 15.
0:12:37 > 0:12:41Right, so... Across there, it's double.
0:12:41 > 0:12:45The question to you, and this is difficult, because you're under the cameras,
0:12:45 > 0:12:48I'm going to ask you how many of these we had to pour into that one,
0:12:48 > 0:12:53which is twice the diameter, would we have to pour in in order to fill this up to the top?
0:12:53 > 0:12:58Ie, what's the ratio of the volumes? Now, I'm going to give you two seconds to think about this.
0:12:58 > 0:13:01I'm going to ask the audience to think about this too,
0:13:01 > 0:13:03but not to shout it out, but to do calculation in your heads.
0:13:03 > 0:13:07Because you all know the formula for the volume of a sphere, don't you?
0:13:07 > 0:13:094/3 Pi r cubed.
0:13:09 > 0:13:14All right, you guys do the calculation, and we'll do the experiment.
0:13:14 > 0:13:16- Go on then. How many do you think? - Eight.
0:13:16 > 0:13:20- Eight? Are you sure?- Yes.
0:13:20 > 0:13:24Oh! Do you think she's right? Who thinks that that is way too many?
0:13:24 > 0:13:27Quite a lot of you. And who thinks it's too few?
0:13:27 > 0:13:31And it's a trick that we've only put nine here? Some of you? Nice. Would we do that?
0:13:31 > 0:13:33Maybe we would. Let's go. Have a go.
0:13:33 > 0:13:35You think eight.
0:13:40 > 0:13:45That's one... Although this isn't going up very fast.
0:13:45 > 0:13:46That's two.
0:13:46 > 0:13:49All right, that's three.
0:13:49 > 0:13:52Four. It's looking good for you, isn't it.
0:13:52 > 0:13:55That's five. And you're getting nervous...
0:13:55 > 0:13:58A little bit. That's six.
0:13:58 > 0:14:00This is seven.
0:14:00 > 0:14:02Here we go. Oh...
0:14:02 > 0:14:05Now, the question is, will it be eight, and are you going to be victorious?
0:14:05 > 0:14:09And if you are, are you going to run up the stairs shouting, "Yippee"?
0:14:09 > 0:14:11Yes!
0:14:17 > 0:14:19You! You!
0:14:20 > 0:14:22Thank you very much for that.
0:14:22 > 0:14:24Do have a seat again.
0:14:24 > 0:14:26So, it's quite surprising, don't you think?
0:14:26 > 0:14:32You increase something twice, the width or diameter twice,
0:14:32 > 0:14:36and your volume increases by eight times.
0:14:36 > 0:14:38Oh, crash-test dog is back!
0:14:38 > 0:14:42He's bandaged up. He survived.
0:14:42 > 0:14:44The show must go on, mustn't it.
0:14:44 > 0:14:47How are you feeling? Oh, not too talkative.
0:14:47 > 0:14:54Fair enough. So, how does this all relate to crash-test dog and crash-test hamster? Well...
0:14:54 > 0:14:58they're different sizes, so how different in sizes are they?
0:14:58 > 0:15:03Well... Crash-test hamster is about five and a bit.
0:15:06 > 0:15:10And crash-test dog is about 25 and a bit.
0:15:10 > 0:15:14Crash-test dog is five times bigger than crash-test hamster.
0:15:14 > 0:15:18If you do the maths in your head - are you doing it up there now?
0:15:18 > 0:15:24It turns out that crash-test dog is 100 times bigger volume than crash-test hamster.
0:15:24 > 0:15:27100 times.
0:15:27 > 0:15:31OK, so that would mean, if that's true, that would mean that
0:15:31 > 0:15:35crash-test dog is 100 times heavier than crash-test hamster.
0:15:35 > 0:15:38Force of gravity on it's going to be 100 times heavier.
0:15:38 > 0:15:40Do you guys believe me on that one?
0:15:40 > 0:15:42Do you think that's at all believable?
0:15:42 > 0:15:45100 times heavier?
0:15:45 > 0:15:47Well, I've got some scales here.
0:15:47 > 0:15:49Let's just have a look at that.
0:15:49 > 0:15:50Let's measure it.
0:15:50 > 0:15:55Crash-test hamster is about 100 grams.
0:15:55 > 0:15:59Crash-test dog, even injured, with his bandage,
0:15:59 > 0:16:04so it's a bit unfair cos he's got a bit more weight,
0:16:04 > 0:16:06just over 10 kilos.
0:16:06 > 0:16:12Crash-test dog is slightly more than 100 times bigger than crash-test hamster.
0:16:12 > 0:16:15Sorry, 100 times heavier. Does that answer our question,
0:16:15 > 0:16:19why crash-test dog had such a hard time when he hit the floor?
0:16:19 > 0:16:25Because he was 100 times heavier he had 100 times more force hurtling him down to the floor.
0:16:25 > 0:16:29It's not the whole story, because when you hit the floor,
0:16:29 > 0:16:35you can basically spread your weight and the force of impact over a large area.
0:16:35 > 0:16:39So, the pressure on every part of you would be reduced, OK.
0:16:39 > 0:16:43So, it's not just how much force you hit the floor with,
0:16:43 > 0:16:45it's how much you can spread it out.
0:16:45 > 0:16:48That's about area, isn't it, this kind of thing called area.
0:16:48 > 0:16:53We really want to know whether crash-test dog is 100 times bigger area,
0:16:53 > 0:16:57whether the outside of crash-test dog is 100 times bigger area
0:16:57 > 0:16:59than crash-test hamster, don't we?
0:16:59 > 0:17:03That's what we really want to know. What we did earlier, we scanned in,
0:17:03 > 0:17:06with a 3D scanner, these two animals,
0:17:06 > 0:17:10and we worked out their area. We've got them here.
0:17:10 > 0:17:15Surface area of crash-test hamster is 100.
0:17:15 > 0:17:20Surface area of crash-test dog is 2,800.
0:17:22 > 0:17:25That's a bit concern-making now.
0:17:25 > 0:17:28Now we're starting to get worried for crash-test dog.
0:17:28 > 0:17:31Too late, I know what you're saying.
0:17:31 > 0:17:34The area over which it could spread that force has only gone up
0:17:34 > 0:17:38by essentially 28 times, but the weight has gone up by 100 times.
0:17:38 > 0:17:43This tells you something really fundamental about making things bigger.
0:17:43 > 0:17:49It's that the area to volume ratio changes when you get bigger.
0:17:49 > 0:17:55So, as you get bigger, it turns out that your area doesn't keep up with your volume.
0:17:55 > 0:17:59You get more inside and you get less and less outside proportionally.
0:17:59 > 0:18:03That really means that when you hit the ground,
0:18:03 > 0:18:07you've got less area to spread that force over. We have an action replay.
0:18:07 > 0:18:14I know you've all been waiting for this action replay, of the rather unfortunate accident that happened.
0:18:14 > 0:18:20This is crash-test hamster coming down and spreads its weight over a large area and survives.
0:18:20 > 0:18:22We knew it survived.
0:18:22 > 0:18:25It was OK. Now we go to crash-test dog.
0:18:25 > 0:18:30What happens is, crash-test dog comes down, tries to spread.
0:18:30 > 0:18:33It got 100 times more force,
0:18:33 > 0:18:36but it's only got 28 times more area, and basically
0:18:36 > 0:18:39the pressure on all its extremities
0:18:39 > 0:18:46couldn't cope and it split, but luckily we could rebuild him and he seems to be on the mend.
0:18:46 > 0:18:48So, there it is.
0:18:48 > 0:18:55It turns out one of the reasons why it gets easier for you to survive a fall when you're smaller,
0:18:55 > 0:18:59because you've got a lot of area and not very much volume.
0:18:59 > 0:19:03So, your surface area to volume ratio is very high.
0:19:03 > 0:19:05There's something else that helps you too.
0:19:05 > 0:19:12Because we've kind of gone on the assumption that they hit the floor at the same speed, but did they?
0:19:12 > 0:19:15Things don't always fall at the same speed.
0:19:15 > 0:19:19I want to just show you something about that, here, with this demo.
0:19:19 > 0:19:21I've got a snowflake
0:19:21 > 0:19:24and I've got a snowball.
0:19:24 > 0:19:29Well, they're not really snow, but they represent them.
0:19:29 > 0:19:35They're exactly the same weight, but they won't fall...
0:19:35 > 0:19:38Well, let's see. Will they fall at the same speed?
0:19:38 > 0:19:41OK... No, they won't. So, that's interesting because
0:19:41 > 0:19:47basically, they have the same force pushing them down, pulling them down, of gravity,
0:19:47 > 0:19:49because they've got the same weight.
0:19:49 > 0:19:52But this one has more area, so it has more air resistance.
0:19:52 > 0:19:57So, if you think about that with regards to small hamsters,
0:19:57 > 0:20:02not only when they hit the ground do they have more area to spread it over,
0:20:02 > 0:20:07when they come down, they slow down quicker because their surface to volume ratio is really good.
0:20:07 > 0:20:11We know this. Snow falls very gently.
0:20:11 > 0:20:14If you take the same volume of liquid and you make it
0:20:14 > 0:20:17into a drop of rain, it hits quite hard actually.
0:20:17 > 0:20:20It hits the top of my head very hard, I can tell you!
0:20:20 > 0:20:22That's the price you pay for being a bit bald.
0:20:22 > 0:20:25Let's not go into that, thanks for bringing it up.
0:20:25 > 0:20:29So, we know the rules now.
0:20:29 > 0:20:35The rules of falling are that surface to volume ratio is king. You really need to know this.
0:20:35 > 0:20:40If I, instead of hamster, was jumping off the tallest building, if it was me,
0:20:40 > 0:20:43then I could manipulate the rules maybe.
0:20:43 > 0:20:46Let's say I jump off the building.
0:20:46 > 0:20:50I'm falling through the air,
0:20:50 > 0:20:54and then I realise that I haven't got a big enough surface to volume ratio.
0:20:54 > 0:20:58Doesn't that always happen after you jump?!
0:20:58 > 0:21:00So, I think, Hamish!
0:21:00 > 0:21:02Chuck me the umbrella! Thanks.
0:21:02 > 0:21:07Hamish chucks me the umbrella, and now I've increased my area.
0:21:07 > 0:21:10So, I'm going to slow down,
0:21:10 > 0:21:12and I fall much slower.
0:21:12 > 0:21:16I basically am cheating. I am increasing my area artificially.
0:21:16 > 0:21:20This, of course, is the essence of a parachute.
0:21:20 > 0:21:22So, parachutes work because they change...
0:21:22 > 0:21:24You cheat, you change your surface to area ratio.
0:21:24 > 0:21:29You add a lot of area, and don't really change your weight very much, or volume very much.
0:21:29 > 0:21:30So, that's really cool.
0:21:30 > 0:21:34When you're parachuting, what you're doing is becoming a hamster.
0:21:34 > 0:21:38OK? Parachutists don't talk about it like that.
0:21:38 > 0:21:40It's much more of a gung-ho sport.
0:21:40 > 0:21:43But that's really what's happening.
0:21:43 > 0:21:47So, it's not just actually that it helps you jump off buildings,
0:21:47 > 0:21:50this ratio, and survive falls.
0:21:50 > 0:21:52It's really important in your whole life.
0:21:52 > 0:21:57How many of you are fed up with people saying to you, "Oh God, you've grown!"?
0:21:57 > 0:22:00Or, "How tall are you now?" You're like, ugh!
0:22:00 > 0:22:02Why are you obsessed with my height?
0:22:02 > 0:22:07Ugh! That kind of thing. People constantly measuring your height...
0:22:07 > 0:22:09Next time, I've got a good line for you guys.
0:22:09 > 0:22:14Just say, "Don't worry about my height. It's my surface to volume ratio you should worry about."
0:22:14 > 0:22:19When I was a kid, I used to go to the swimming pool with my brothers, who are all bigger than me.
0:22:19 > 0:22:24I used to start shivering about 10 minutes in, freezing cold. I went blue with cold.
0:22:24 > 0:22:27And they were totally fine, swimming around for hours.
0:22:27 > 0:22:31I always used to think, they're so much stronger, tougher than me.
0:22:31 > 0:22:35But actually, they just had a lower surface to volume ratio.
0:22:35 > 0:22:41So, your area is what cools you, as a person, so that you evaporate water off you.
0:22:41 > 0:22:45It's your volume that gives you the warmth, the blood, and all those kind of things.
0:22:45 > 0:22:49If you haven't got very much volume, but a lot of area, you'll cool down fast.
0:22:49 > 0:22:51So you're going to shiver.
0:22:51 > 0:22:57So the bigger you get, the less cold you'll get in swimming pools. This is also true of babies.
0:22:57 > 0:23:02People are always dressing up babies with 10 coats, and you're like, don't mollycoddle them.
0:23:02 > 0:23:06But they've got a terrible surface to volume ratio when it comes to cold.
0:23:06 > 0:23:09You really do need to put coats on them.
0:23:09 > 0:23:12So, that's us manipulating surface to volume ratio.
0:23:12 > 0:23:15But could we find examples
0:23:15 > 0:23:18of nature manipulating it in other ways?
0:23:18 > 0:23:22We found one the other day when I was on holiday.
0:23:22 > 0:23:24I was looking at the ceiling
0:23:24 > 0:23:29in Dubai, and this gecko was walking across the ceiling.
0:23:29 > 0:23:31I was thinking, how can it do that?
0:23:31 > 0:23:33That's really mad.
0:23:33 > 0:23:35And so,
0:23:35 > 0:23:41I kind of went home and I started doing some research about how geckos can stick on the ceiling.
0:23:41 > 0:23:44Hello. We've got a gecko with us, haven't we?
0:23:44 > 0:23:45- Yes.- Gordon Gecko.
0:23:45 > 0:23:48He's in there, isn't he? And what kind of gecko is he?
0:23:48 > 0:23:51He's a Tokay gecko, the largest type you can get.
0:23:51 > 0:23:56- OK, brilliant. He is able to walk up walls, isn't he?- He is indeed.
0:23:56 > 0:24:01Pretty amazing, isn't it? We've a guest who can walk up walls, everybody! Can we have a look?
0:24:01 > 0:24:03- Would he have a go?- Yeah, sure. - Will he be camera shy?
0:24:03 > 0:24:07I'll give him a go.
0:24:07 > 0:24:08Might be a bit noisy.
0:24:11 > 0:24:14There he goes. He looks a bit annoyed.
0:24:14 > 0:24:17- Is he a bit annoyed?- He's all right.
0:24:17 > 0:24:19They do have a bit of a temper on them.
0:24:19 > 0:24:21Is it because he hasn't eaten or something?
0:24:21 > 0:24:23- No, he's all right. - He's been eating, OK.
0:24:23 > 0:24:27- Because I get a bit annoyed. Anyway...- Ready?
0:24:27 > 0:24:29There he is! Look at that!
0:24:29 > 0:24:33APPLAUSE
0:24:40 > 0:24:42Now, how on earth does he do that?
0:24:42 > 0:24:46That is so brilliant. Well done. That is so amazing.
0:24:46 > 0:24:48Now, you hang on there. Will he be all right?
0:24:48 > 0:24:50- Can we just leave him there?- Yes.
0:24:50 > 0:24:55Amazing. Isn't it amazing? So let's think about how a gecko can do this.
0:24:55 > 0:24:57I was thinking in my hotel room,
0:24:57 > 0:25:00I was having a word with Hamish the hamster,
0:25:00 > 0:25:03and we came up with four possible explanations.
0:25:03 > 0:25:05I'll run him past you, then we'll do a vote.
0:25:05 > 0:25:08So you guys can run with me on this one.
0:25:08 > 0:25:10We thought that it may be
0:25:10 > 0:25:14that geckos have some sort of glue on their paws.
0:25:14 > 0:25:17A bit like a spider squirting out glue,
0:25:17 > 0:25:20and that's how they can walk up walls.
0:25:20 > 0:25:23So that is option number one for you to think about.
0:25:24 > 0:25:28Option number two is that they actually have nails.
0:25:28 > 0:25:32Well, not nails, but something spiky, all right?
0:25:32 > 0:25:34And that's how they get up these walls.
0:25:34 > 0:25:37- Is he all right?- Yeah, he's fine.
0:25:37 > 0:25:40I'm talking about you, gecko.
0:25:40 > 0:25:41Yes, yes!
0:25:43 > 0:25:47Option number three is that - and this is my favourite -
0:25:47 > 0:25:49that they have little suckers on them,
0:25:49 > 0:25:53like the stuff you put onto bathrooms and things like that.
0:25:53 > 0:25:56Suckers, impressed? Well, all right.
0:25:56 > 0:26:01And option number four, they have some sort of weird hairs on them, weird kind of hairs.
0:26:01 > 0:26:05We ran out of ideas by that point! OK, weird hairs.
0:26:05 > 0:26:11Let's have a vote. Who thinks it is bits of glue, a bit like a spider squirting out glue. Anyone?
0:26:11 > 0:26:14Who votes for that? Oh, no-one.
0:26:14 > 0:26:17Who votes for the nails.
0:26:17 > 0:26:19Come on! It was quite a good idea.
0:26:19 > 0:26:20No?
0:26:20 > 0:26:24Who votes for suckers?
0:26:24 > 0:26:25Suckers!
0:26:25 > 0:26:29Maybe, maybe. I'm not giving anything away.
0:26:29 > 0:26:31And who votes for the hairs?
0:26:31 > 0:26:35So we're sort of equally split in this audience between hairs and suckers.
0:26:35 > 0:26:37Not often you get to say that, is it?
0:26:37 > 0:26:42So, Gordon, do you want to tell us how you do it? No, you don't. All right.
0:26:44 > 0:26:48All right, so... let's see how he does it.
0:26:48 > 0:26:51Let's have a look under the microscope.
0:26:51 > 0:26:56We found a microscopic image of the paws of a gecko and we've got it over here.
0:26:56 > 0:27:01When you actually look under the microscope at these paws of the gecko,
0:27:01 > 0:27:04this is really high magnification,
0:27:04 > 0:27:08you get this thing, it looks a bit like celery, or rhubarb.
0:27:08 > 0:27:11Now if you zoom even further in... Yes, look, hairs!
0:27:11 > 0:27:13Actually hairs on the end of hairs.
0:27:13 > 0:27:16It's hairs on hairs
0:27:16 > 0:27:19is what this gecko's paws are under the microscope.
0:27:19 > 0:27:21This gecko has hairy hands.
0:27:21 > 0:27:25However ludicrous that sounded, it is the truth.
0:27:25 > 0:27:27So that's really mad, isn't it?
0:27:28 > 0:27:31OK, well, look....before we go on,
0:27:31 > 0:27:35I'm just going to let Gordon go, because he looks like
0:27:35 > 0:27:39he's kind of, yeah, he wants to have a bit of a rest, doesn't he?
0:27:47 > 0:27:48Thank you very much.
0:27:50 > 0:27:54Geckos climb up walls using hairy hands.
0:27:54 > 0:28:00That hasn't told us anything, has it? That's HOW it works, but why does that work?
0:28:00 > 0:28:03What's going on there?
0:28:03 > 0:28:07So I want to do a demo now, which is going to try and...
0:28:07 > 0:28:09eke that out. What's really going on here?
0:28:09 > 0:28:13I'm going to need six - can you believe it? - I need six volunteers.
0:28:13 > 0:28:18I need three boys, the strongest boys in the world, and three girls, the strongest girls in the world.
0:28:18 > 0:28:23OK, so, boy there - yes. And, go on,
0:28:23 > 0:28:25the dog denier.
0:28:27 > 0:28:31That girl there, yes, yes, you. Yes!
0:28:31 > 0:28:35OK. Girl power versus boy power.
0:28:35 > 0:28:39Now, what we've got here is two health and safety manuals.
0:28:42 > 0:28:47If I send that... You can hold that rope, and you guys hold that rope.
0:28:47 > 0:28:49Have you got a bit of the rope? You need to go in a line.
0:28:49 > 0:28:53You're going to pull against each other. Are you ready?
0:28:53 > 0:28:55Two health and safety manuals.
0:28:55 > 0:28:58All we've done with them is interleave the pages.
0:28:58 > 0:29:03There's no glue, no bolts. Just inter-leave the pages.
0:29:03 > 0:29:07What I want you to do is rip these apart. All right?
0:29:07 > 0:29:13In doing so, you guys humiliate the boys by pulling them across here.
0:29:13 > 0:29:17You guys, you know, girl power, boy power.
0:29:17 > 0:29:19Right, ready? Are you guys ready?
0:29:19 > 0:29:21Steady... Go!
0:29:21 > 0:29:23Yes! And the girls are really holding on!
0:29:23 > 0:29:26What's happening to this?
0:29:26 > 0:29:28What is happening to this? Come on!
0:29:28 > 0:29:29Yes!
0:29:29 > 0:29:31SHOUTING AND CHEERING
0:29:38 > 0:29:42OK, OK. Wow, that's a dead heat, I think.
0:29:42 > 0:29:44Well done, guys.
0:29:44 > 0:29:48What also won here was these books.
0:29:48 > 0:29:52Yes, I know. Are you all right?
0:29:52 > 0:29:55- They always win.- Yes, they always win. You have to get used to that.
0:29:55 > 0:29:59Now, look, do you believe me that there's no glue here?
0:30:00 > 0:30:04HE BLOWS
0:30:11 > 0:30:13Have a look at that. Look at that.
0:30:15 > 0:30:16OK?
0:30:19 > 0:30:21That's mad, isn't it?
0:30:21 > 0:30:24No glue, right? Just paper, no glue?
0:30:24 > 0:30:26- No.- So, that's incredible, isn't it?
0:30:26 > 0:30:29It turns out that even though you guys are really strong,
0:30:29 > 0:30:33you'd need two tanks pulling in opposite directions to pull this apart.
0:30:33 > 0:30:36Amazing, isn't it? Well, thanks a lot.
0:30:36 > 0:30:38You can go back to your seats. Thanks, guys.
0:30:45 > 0:30:49Next time you're in a burning building and you're thinking there's no way out
0:30:49 > 0:30:53and you start going for the sheets and knotting them together, don't do it.
0:30:53 > 0:30:56Get the telephone directories, all right?
0:30:59 > 0:31:06So, look, how does that work and how can that help us understand the gecko?
0:31:06 > 0:31:08Why is it such a strong force?
0:31:08 > 0:31:13Well, it turns out that what's keeping those pieces of paper together
0:31:13 > 0:31:16is tiny molecular forces between the two sheets.
0:31:16 > 0:31:22And the forces are very small, but if you maximise them over lots of area,
0:31:22 > 0:31:26so if you can times a small force by a large area you get a decent force
0:31:26 > 0:31:29and by having every single piece of paper over each other
0:31:29 > 0:31:32we actually managed to get a large area of interface there, didn't we?
0:31:32 > 0:31:39So...could it be that the gecko is using the same idea to climb up walls?
0:31:39 > 0:31:43Well, what does a wall look like when it's magnified up?
0:31:43 > 0:31:46This is not a picture of the Alps, but it might be, right?
0:31:46 > 0:31:49This is what happens if you magnify a wall.
0:31:49 > 0:31:53It made look smooth to you, and you may run your finger across a wall
0:31:53 > 0:31:55or a surface and think that's quite smooth.
0:31:55 > 0:32:00But under the microscope, surfaces are very rough.
0:32:00 > 0:32:02They look like mountains, right?
0:32:04 > 0:32:06So, if you're touching something...
0:32:06 > 0:32:08So, this is a massive me.
0:32:08 > 0:32:12This is what my thumb looks like. See, quite nicely groomed!
0:32:12 > 0:32:16And if I'm touching the wall and I'm trying to climb up it,
0:32:16 > 0:32:19if I want to use the same force as with the book demo,
0:32:19 > 0:32:23I need to maximise my area of contact, so I try to do that.
0:32:23 > 0:32:29I'm pressing my finger in here, but you can see that, actually, all I ever do is
0:32:29 > 0:32:32just touch the tips of the mountain
0:32:32 > 0:32:37and it's really very hard for me to do anything else and so, ultimately,
0:32:37 > 0:32:41I get very little contact with the wall in terms of area,
0:32:41 > 0:32:43and so I don't get any kind of help.
0:32:43 > 0:32:48And, you know, this is also true of when you touch anything.
0:32:48 > 0:32:53You touch a surface and you think you're touching it, you're mostly just touching the tips of mountains.
0:32:53 > 0:32:57We very rarely really touch things, but the gecko knows better.
0:32:57 > 0:33:01The gecko has hairy hands, so if you were to zoom in on a gecko's paw,
0:33:01 > 0:33:07we've already seen that, he's got these amazing hairs, so look what the gecko does.
0:33:07 > 0:33:12The gecko gets onto the wall, the wall is rough, but that's no problem
0:33:12 > 0:33:17because the hairs get right down into the valleys, right?
0:33:17 > 0:33:20They are maximising an area of contact there,
0:33:20 > 0:33:23so even though there's no adhesive force in terms of glue
0:33:23 > 0:33:26or any kind of mechanical scratching, it's just the same force,
0:33:26 > 0:33:29these surface forces, which are tiny,
0:33:29 > 0:33:33but you maximise the area of contact and you can climb up walls.
0:33:33 > 0:33:35So well done, gecko, for working that one out.
0:33:35 > 0:33:36That's pretty impressive!
0:33:44 > 0:33:48I know what you're thinking. You're thinking, you material scientists,
0:33:48 > 0:33:51why don't you make some gloves like a gecko's hand, hairy gloves,
0:33:51 > 0:33:54then we can all just walk up walls and be Spiderman, right?
0:33:54 > 0:33:58I know what you're thinking. Well, it's not so far from the truth.
0:33:58 > 0:34:02I've got here the latest sample from a lab in California
0:34:02 > 0:34:04which is trying to do exactly that.
0:34:04 > 0:34:09It's just a prototype at the moment. I'll show you what it looks like under the microscope.
0:34:09 > 0:34:11If we go here and we look in...
0:34:11 > 0:34:16what they've done is engineered a material that has these filaments,
0:34:16 > 0:34:21and when they're pressed against the wall, they bend and they make huge contact with that wall.
0:34:21 > 0:34:26It just feels very smooth and flat, but you can just
0:34:26 > 0:34:28stick things onto it.
0:34:29 > 0:34:32Oh! It's a prototype, OK?
0:34:32 > 0:34:35No, it does work, actually.
0:34:35 > 0:34:36There it is. Yes!
0:34:36 > 0:34:40So, actually the future could be that we have these amazing gloves,
0:34:40 > 0:34:45but there is one problem with that future, and I want to show you that problem with that future
0:34:45 > 0:34:52with this enormous piece of Blu-Tack, because this stuff, you know, right?
0:34:52 > 0:34:55And you're thinking Blu-Tack, yawn. But it's actually
0:34:55 > 0:34:59as sophisticated as the gecko's foot because it works in the same way.
0:34:59 > 0:35:04You take a small piece of Blu-Tack, and this stuff is not sticky, it's not got adhesive in it, has it?
0:35:04 > 0:35:07You could infinitely reuse this stuff.
0:35:07 > 0:35:13It's not like a piece of Sellotape or sticky tape where actually after a while it loses its stick.
0:35:13 > 0:35:16So, how does that work? Well, it's the same as the gecko's foot.
0:35:16 > 0:35:21It's a material that becomes liquid when you put pressure on it
0:35:21 > 0:35:24and that liquid flows into the mountains,
0:35:24 > 0:35:26the rough mountains of this surface,
0:35:26 > 0:35:29and then it maximises the area of contact,
0:35:29 > 0:35:33uses the same adhesive forces, these weak surface forces, and sticks.
0:35:33 > 0:35:39You use this all the time and it's the same as a gecko's foot. So, that's fantastic!
0:35:39 > 0:35:45And then you think, well, OK, I'm just going to go home and I'm going to just cover myself in Blu-Tack.
0:35:45 > 0:35:47I know you guys!
0:35:47 > 0:35:50But don't do it, because from what you've learned tonight
0:35:50 > 0:35:52you already know there's a problem.
0:35:52 > 0:35:55Which is that although the adhesive force goes up,
0:35:55 > 0:36:00if your volume isn't matching that force,
0:36:00 > 0:36:03if your volume's going up quicker, then it's going to override it.
0:36:03 > 0:36:06So if you try and stick this whole piece of Blu-Tack...
0:36:06 > 0:36:11I'm putting pressure on it, doing all the adhesive stuff, but this volume is very large, isn't it?
0:36:11 > 0:36:14So the force downwards is too big for that adhesive force.
0:36:14 > 0:36:19OK, so it's not an accident that geckos are small,
0:36:19 > 0:36:23because they've got low weight and it's all about this ratio, this surface to volume ratio.
0:36:23 > 0:36:28So we need something even better than geckos in order for us to be like Spiderman.
0:36:28 > 0:36:31But it think we can do it, it's just a matter of time.
0:36:31 > 0:36:34OK, so, fantastic!
0:36:34 > 0:36:38Surface to volume ratio - and I know I keep going on about it -
0:36:38 > 0:36:43but it really is absolutely crucial to your life and no more so than this demo is going to show you.
0:36:45 > 0:36:51Under this here I've got a model and it's a model of my lungs, OK?
0:36:51 > 0:36:54This are what my lungs looked like.
0:36:54 > 0:36:55I'm going to put it exactly...
0:36:55 > 0:36:59There we go. No, there we go!
0:36:59 > 0:37:00Now, I'm breathing in,
0:37:00 > 0:37:03and these lungs are exactly the right size for me,
0:37:03 > 0:37:05so air is coming into these lungs.
0:37:05 > 0:37:08Now, would you believe that this is big enough? Probably not.
0:37:08 > 0:37:13When you're breathing in now, you're breathing a large volume of air, so if we all breathe in now
0:37:13 > 0:37:16we're all breathing stuff into this kind of structure.
0:37:16 > 0:37:19Now, at that moment... Breathe out everyone, I don't want you fainting!
0:37:19 > 0:37:23At that moment you breathe in,
0:37:23 > 0:37:27your body has to extract all the oxygen it needs to be alive, right?
0:37:27 > 0:37:29So it's taking oxygen from a large volume
0:37:29 > 0:37:33and it has to get into the blood vessels, which is a large area.
0:37:33 > 0:37:38So, basically, it has to find a way of interfacing that large volume of air into all the blood vessels.
0:37:38 > 0:37:42It does this by making these tiny sacs, these alveolar sacs,
0:37:42 > 0:37:46and it spreads them all out in a kind of filigree way
0:37:46 > 0:37:50and it's just like with the hamster, as you get smaller, these little sacs are like spheres.
0:37:50 > 0:37:55As they get smaller, their area in proportion to their volume gets larger and larger.
0:37:55 > 0:37:56That's exactly what you want.
0:37:56 > 0:38:00You want a large area to interface with the oxygen, right?
0:38:00 > 0:38:03To get the oxygen into your blood and get the carbon dioxide out.
0:38:03 > 0:38:09So, your own body is using the surface to volume ratio to actually just let you live!
0:38:09 > 0:38:13And I want to show you how big this area is that you need to live
0:38:13 > 0:38:15because you can't really see it here
0:38:15 > 0:38:18because you're seeing it as a volume, right?
0:38:18 > 0:38:22But if you spread all these out on to a sheet, how big would that sheet be?
0:38:22 > 0:38:25Well, let me show you how big that sheet would be.
0:38:25 > 0:38:27OK, we've got it here.
0:38:27 > 0:38:31Right, I'm going to take this up, am I? Yes.
0:38:31 > 0:38:34I'm going to, basically, spread this sheet out.
0:38:34 > 0:38:36This piece of silk is the same area as my lungs.
0:38:36 > 0:38:40Would you believe it? It's just inconceivable, isn't it,
0:38:40 > 0:38:42that all this area could be inside your body.
0:38:42 > 0:38:45I want you to pass this around. Is that possible?
0:38:45 > 0:38:49Yes! It's quite nice being in my lungs, isn't it? Keep going, guys. Keep going.
0:38:49 > 0:38:53Right, you guys let go. Let it go.
0:38:53 > 0:38:57My lungs, ladies and gentlemen. There's a small hole.
0:38:57 > 0:39:00Can any of you spot the small hole? That's where I used to smoke.
0:39:00 > 0:39:03Essentially, that is what happens when you smoke -
0:39:03 > 0:39:06your lung area gets smaller and smaller, so you get out of breath.
0:39:06 > 0:39:09So, if you get out of breath and you have lung disease,
0:39:09 > 0:39:13you get a smaller area in which to absorb oxygen, and that's the problem.
0:39:13 > 0:39:18Maximising your area of your lungs is incredibly important to you.
0:39:18 > 0:39:20So, this whole thing is incredible.
0:39:20 > 0:39:22The surface to volume ratio, right?
0:39:22 > 0:39:29The area to volume ratio is so important to you. It can help you survive jumping off a building.
0:39:29 > 0:39:32It can help geckos climb up walls.
0:39:32 > 0:39:36It can do all sorts of things. It's integral to how you breathe and live,
0:39:36 > 0:39:39but it does something even more important than that.
0:39:39 > 0:39:42It can determine whether you can dance or not.
0:40:17 > 0:40:19Whoa!
0:40:27 > 0:40:31The dancers from Strictly Come Dancing! You're from Strictly Come Dancing, aren't you?
0:40:31 > 0:40:34- We're the choreographers of the show, yes.- What are you names?
0:40:34 > 0:40:36Chris Marquez, Jaclyn Spencer.
0:40:36 > 0:40:39Fantastic. You dance so brilliantly.
0:40:39 > 0:40:44I'm so envious. And, in fact, I made some notes and...
0:40:44 > 0:40:49I just wanted to run these past you because I've come up with three rules having watched you
0:40:49 > 0:40:52about what you need to be able to do to dance.
0:40:52 > 0:40:56- You can critique them and see if I'm on the right track.- All right.
0:40:56 > 0:41:00Is that OK? So, one of the rules of being able to dance is just to be able to stand.
0:41:00 > 0:41:04You're standing now and if you couldn't, it would be difficult. So it seems a prerequisite.
0:41:04 > 0:41:05- Yeah.- You've got to be able to stand.
0:41:05 > 0:41:11Then I noticed that you were jumping from foot to foot and there was kind of jigging around
0:41:11 > 0:41:13and that seems to need a lot of strength in your legs.
0:41:13 > 0:41:15Yeah, you need to be able to move your weight.
0:41:15 > 0:41:20- Weight transfer in general is very important, obviously, to dancing, yes.- Yes, OK.
0:41:20 > 0:41:25And you had to be strong enough to pick up your partner, so that's also weight on the legs.
0:41:25 > 0:41:28- It all goes through here.- Again, the legs, but often you find that the whole tone in the body.
0:41:28 > 0:41:30So, standing up, strength, jumping.
0:41:30 > 0:41:33If I can do those things, I can dance.
0:41:33 > 0:41:36Well, yes, with a bit of rhythm and...
0:41:36 > 0:41:39I'm going to work on those rules for a bit now
0:41:39 > 0:41:46- and then I'm going to come back to you at the end, but before you go, I just want to get the scores.- Ten.
0:41:46 > 0:41:48- Ten.- Ten.- Ten.- Bring it on!
0:41:54 > 0:41:57OK, so...
0:41:57 > 0:42:00Now, look, standing!
0:42:00 > 0:42:02That doesn't seem too hard, does it?
0:42:02 > 0:42:05But is it? Is it as simple as that?
0:42:05 > 0:42:09I'm back to spherical animals because, basically, if you ask
0:42:09 > 0:42:12a physicist to do anything they'll end up starting with a sphere.
0:42:12 > 0:42:16So, my model for an animal is a sphere, but this time legs.
0:42:16 > 0:42:17That's a step forward, literally!
0:42:17 > 0:42:22So, now, I've got a spherical animal and all of its weight
0:42:22 > 0:42:24has got to go through its legs, OK?
0:42:24 > 0:42:29So that means that these legs are like the pillars of a building, right?
0:42:29 > 0:42:31All of the force is coming through them.
0:42:31 > 0:42:37So, the area, that cross sectional area of those legs, is what's taking all the weight through there.
0:42:37 > 0:42:40So if that's small, then there might not be enough...
0:42:40 > 0:42:43They've got to be strong enough to support the whole weight.
0:42:43 > 0:42:48If I take this animal, all its weight is going through its legs and it's standing on its own feet.
0:42:48 > 0:42:50It's got four legs, fantastic.
0:42:50 > 0:42:52What happens when I size it up -
0:42:52 > 0:42:55I scale it up and increase its width by two.
0:42:55 > 0:42:59So, this is an animal exactly twice as big in proportions,
0:42:59 > 0:43:03so that means, as we know, that its volume has increased by eight times.
0:43:03 > 0:43:07So, that means its weight has increased by eight times.
0:43:07 > 0:43:10That would be fine if the area of its legs
0:43:10 > 0:43:12had increased by eight times -
0:43:12 > 0:43:16then it would be exactly the same, but has the area of its legs increased?
0:43:16 > 0:43:18- What do you think?- No.
0:43:18 > 0:43:24No, it hasn't, because this area, this cross-sectional area, has only got four times bigger
0:43:24 > 0:43:28because of this whole problem of when you size things up the surface to area ratio changes.
0:43:28 > 0:43:33So, every one of the legs of this animal, has twice as much force
0:43:33 > 0:43:37running through it and that means that...
0:43:37 > 0:43:39it can't actually stand up.
0:43:39 > 0:43:44So, the thing is, you can't just keep getting bigger
0:43:44 > 0:43:47as an animal and not change your design because sooner or later
0:43:47 > 0:43:49you will collapse under your own weight.
0:43:49 > 0:43:52Now, you don't think that this happens,
0:43:52 > 0:43:56but actually this is what happens with elephants.
0:43:56 > 0:44:00This is an elephant's leg of a juvenile from India.
0:44:00 > 0:44:05It's about six or seven years old and you can already see,
0:44:05 > 0:44:08and we know this, don't we, that the ratios of the bones
0:44:08 > 0:44:13and the thickness of the bones have changed because this is the way out of the problem.
0:44:13 > 0:44:16If you change the ratios, if you make thicker legs,
0:44:16 > 0:44:19then you can support bigger weights and that's what elephants do.
0:44:19 > 0:44:24They make their bones bigger, they make their legs bigger
0:44:24 > 0:44:27because they actually are in trouble if they don't do that.
0:44:27 > 0:44:33Galileo recognised this very early on and people have noticed this ever since and, in fact, if you look at
0:44:33 > 0:44:40elephants you can immediately see it - proportionally they have much thicker legs and they need it,
0:44:40 > 0:44:44otherwise they start to get into trouble with their ability to hold up their legs.
0:44:44 > 0:44:49And if you look at even bigger things like dinosaurs, they have really fat legs.
0:44:49 > 0:44:52And it's not a style choice, OK?
0:44:52 > 0:44:55What's the problem with having bigger, thicker legs?
0:44:55 > 0:44:57Surely that should make them stronger?
0:44:57 > 0:45:00We thought if we're going to talk about this,
0:45:00 > 0:45:02let's get the strongest person we know and ask them.
0:45:02 > 0:45:09And here he is. This is the strongest person I know, and he is strong! Hello.
0:45:09 > 0:45:12CHEERING AND APPLAUSE
0:45:15 > 0:45:18- So, what's your name? - My name is Terry Hollands.
0:45:18 > 0:45:21And what are your strength credentials, just so we can all...
0:45:21 > 0:45:24I've been England's strongest man, UK's strongest man,
0:45:24 > 0:45:28Britain's strongest man and a five time finalist at World's strongest man.
0:45:28 > 0:45:30CHEERING AND APPLAUSE
0:45:37 > 0:45:40So, you say that...
0:45:40 > 0:45:45- but could you just give us a demonstration of exactly how strong you are?- Yeah, sure.
0:45:45 > 0:45:48I lifted these weights earlier...
0:45:48 > 0:45:49LAUGHTER
0:45:49 > 0:45:52I just thought, well, as a test, I might see if you can lift them, too.
0:45:52 > 0:45:54Yeah.
0:45:54 > 0:45:57- Do you think you could have a go at that?- Yeah, sure.
0:46:04 > 0:46:06DRUM ROLL
0:46:10 > 0:46:12Whoa!
0:46:12 > 0:46:14CHEERING AND APPLAUSE
0:46:25 > 0:46:28Did you see the bar bending?
0:46:28 > 0:46:31- That bar, which is about an inch thick steel, bent.- Yeah.
0:46:31 > 0:46:33That's absolutely amazing.
0:46:33 > 0:46:39I'm so impressed. I want to just get a feel for how much that is compared to your weight.
0:46:39 > 0:46:42Do you mind asking how heavy you are?
0:46:42 > 0:46:43Sure, I'm 180 kilos.
0:46:43 > 0:46:47You're 180 kilos and what did you just lift here?
0:46:47 > 0:46:54- That's 380 kilos.- 380 kilos, so that means that you lifted a bit more than twice your own weight.- Yeah.
0:46:54 > 0:46:58- That's like a small car, isn't it? - Yeah, pretty much a small car.
0:46:58 > 0:47:00- Could you lift a small car? - Yeah, yeah.
0:47:02 > 0:47:03Wow!
0:47:12 > 0:47:16So, basically, you have been able to lift twice your own weight,
0:47:16 > 0:47:21is there anyone who can lift, let's say, five times their own weight?
0:47:21 > 0:47:24Maybe not five times but some of the lighter guys...
0:47:24 > 0:47:30Generally, the bigger you are, the less number of times you can lift your own body weight, basically.
0:47:30 > 0:47:34The lighter guys would be lifting three, maybe three and a half times their weight.
0:47:34 > 0:47:37- The heavier guys would be just over two.- Absolutely fascinating.
0:47:37 > 0:47:43- I'm so happy that you could come on the show and thank you very much for showing us all.- Great.
0:47:43 > 0:47:45Thank you very much.
0:47:45 > 0:47:48Wow! OK, so, that was very interesting there, right?
0:47:48 > 0:47:53If you want to be able to be strong per weight, right, if you want to be
0:47:53 > 0:47:59able to lift many times your own weight, well, it turns out you need to be small and we've got
0:47:59 > 0:48:05the world champions at this and they turn out to be very small and I'd like to introduce you.
0:48:05 > 0:48:08- What's your name, sorry? - My name is Karen Wall.
0:48:08 > 0:48:12- I'm a PhD student at Cambridge University at the moment.- Welcome.
0:48:12 > 0:48:16And I do actually study how ants manage to
0:48:16 > 0:48:19carry large loads.
0:48:19 > 0:48:24Right, so it's ants who are the world champions at lifting many times their own weight.
0:48:24 > 0:48:27Now, just talk us through this. So what kind of ants are these?
0:48:27 > 0:48:31- So these are basically the leaf cutting ants.- Look at this one!
0:48:31 > 0:48:33- Look at that!- Yeah, it's amazing.
0:48:33 > 0:48:34He's showing off, isn't he?
0:48:34 > 0:48:39- He is showing off, yeah.- He knows the cameras are on, doesn't he?
0:48:39 > 0:48:43Are they going to mind if we pick them up? Are they going to get annoyed? If I was carrying
0:48:43 > 0:48:45my sofa up some stairs...
0:48:45 > 0:48:48He might drop it but he might be all right with it. Let's see.
0:48:48 > 0:48:51If some giant picked me up just to weigh me...
0:48:51 > 0:48:53All right.
0:48:53 > 0:48:55Brilliant, OK. Nice one.
0:48:55 > 0:48:57He doesn't look too annoyed.
0:48:57 > 0:48:59He's still got his sofa.
0:48:59 > 0:49:05So now we have 20.5 milligrams.
0:49:05 > 0:49:07OK, 20.5 milligrams together.
0:49:07 > 0:49:10Now, can get just the ant on its own?
0:49:10 > 0:49:13- Let's try. He might get a bit angry, though.- OK, all right.
0:49:13 > 0:49:15I'll try to get him off.
0:49:19 > 0:49:22- They don't like leaving these fragments.- If you put the fragment where he wants it,
0:49:22 > 0:49:25does he get pleased? Is he going to go, "Oh, thanks"?
0:49:25 > 0:49:26I don't think so. He's still getting angry.
0:49:26 > 0:49:28Fair enough. So, put him back on the scale.
0:49:28 > 0:49:30It's just the ant now.
0:49:30 > 0:49:33So we had 20.7 beforehand
0:49:33 > 0:49:35and now we have...
0:49:36 > 0:49:384.9.
0:49:38 > 0:49:41So, he was carrying about four or five times his own weight.
0:49:41 > 0:49:43- Yeah.- Four or five times?
0:49:43 > 0:49:45So the equivalent of even more weights than that.
0:49:45 > 0:49:46And they can even do more.
0:49:46 > 0:49:50They can go up to about 10 times.
0:49:50 > 0:49:55He has been able to carry it, whereas the weightlifter, he couldn't move any more.
0:49:55 > 0:49:58Don't diss the weightlifter, he's still here!
0:50:00 > 0:50:03Thank you very much. I mean, that's absolutely wonderful.
0:50:03 > 0:50:06Thank you for bringing them to see us.
0:50:06 > 0:50:07APPLAUSE
0:50:10 > 0:50:13The reason why ants are so super strong, or seem so super strong
0:50:13 > 0:50:19is because they're so small that they need almost no muscles in their legs to hold them up,
0:50:19 > 0:50:21because they haven't got much volume,
0:50:21 > 0:50:23they haven't got much weight, so almost all of their muscle
0:50:23 > 0:50:27is available for carrying things, and that's just true of everything.
0:50:27 > 0:50:30The smaller you get, the more muscle you have for carrying.
0:50:30 > 0:50:35So, the smaller you get, the stronger you get per weight.
0:50:35 > 0:50:40But there's another animal that's even better than ants
0:50:40 > 0:50:43at doing something else, and that's jumping.
0:50:43 > 0:50:48We realised that before, didn't we? That we have to jump to also be a great dancer, and so it turns out
0:50:48 > 0:50:52that this is also something you can do much better if you're small.
0:50:52 > 0:50:55Now I want to introduce you to a very special guest.
0:50:55 > 0:50:57APPLAUSE
0:50:58 > 0:51:04- My name's Tim and I've got the only genuine flea circus in the UK.- Wow!
0:51:05 > 0:51:08APPLAUSE AND CHEERING
0:51:08 > 0:51:11So, are we actually going to see some fleas?
0:51:11 > 0:51:13Yeah, I've brought some performers with me.
0:51:13 > 0:51:16We're going to have a demonstration of flea jumping.
0:51:16 > 0:51:19These are untethered and untrained fleas.
0:51:21 > 0:51:23But they won't get out of this?
0:51:23 > 0:51:25No, hopefully not. Fingers crossed.
0:51:25 > 0:51:30Don't worry, guys. We checked this earlier and there's no way they can get out of here.
0:51:30 > 0:51:32This is like Colditz for fleas.
0:51:32 > 0:51:39So we're going to stick one of the fleas on top of the diving board, which is just here.
0:51:42 > 0:51:44And there it goes.
0:51:44 > 0:51:46Where did it go?
0:51:47 > 0:51:49Oh, there it is! How far did it jump?
0:51:49 > 0:51:51- That's incredible! - About 30 centimetres.- Wow!
0:51:51 > 0:51:55Look, we recorded something earlier about flea-jumping.
0:51:55 > 0:52:00I just want to show that on this because it's amazing to see them jumping. Here we go.
0:52:00 > 0:52:05Look at them, he's ready to jump, he's ready to jump and off he goes.
0:52:05 > 0:52:07He comes behind here somewhere.
0:52:07 > 0:52:10It's absolutely amazing, isn't it?
0:52:10 > 0:52:12So, how far can they jump?
0:52:12 > 0:52:15These fleas, about 30 centimetres, so several hundred times their own body length.
0:52:15 > 0:52:18Like me jumping to the top of Big Ben, right?
0:52:18 > 0:52:21- Absolutely. You could clear Big Ben. - Clear it!
0:52:21 > 0:52:24- So we wouldn't need stairs, lifts, if we were fleas.- Absolutely.
0:52:24 > 0:52:29- They're so good, they spend their time mucking about in the circus, do they?
0:52:29 > 0:52:32- Yeah.- How do you feed them?
0:52:32 > 0:52:37Well, like the old flea circus owner said, "I live off them and they live off me."
0:52:37 > 0:52:38AUDIENCE GROANS
0:52:38 > 0:52:44- They suck your blood?- I roll up my sleeves and take one for the team. - No! That's amazing, isn't it?
0:52:44 > 0:52:47That is love, that is love!
0:52:47 > 0:52:51So I'm really glad that you look after these fleas.
0:52:51 > 0:52:54So, on circus-performing front, what can we see?
0:52:54 > 0:52:59- Are they up for it?- The performer I brought today is Fifi. Fifi the flea.
0:52:59 > 0:53:01Fifi is a juggling flea.
0:53:01 > 0:53:02- Oh!- Oops.
0:53:02 > 0:53:04I'll have to pick her up.
0:53:06 > 0:53:08Oh, there she goes!
0:53:10 > 0:53:12No, that's amazing!
0:53:12 > 0:53:13That's amazing.
0:53:14 > 0:53:16AUDIENCE GASPS
0:53:20 > 0:53:24Fifi the flea! Wow!
0:53:27 > 0:53:33- It was a great pleasure meeting you and meeting your fleas and seeing how far they can jump.- Thank you.
0:53:33 > 0:53:35- Thank you very much.- Thank you.
0:53:40 > 0:53:44So, we talked about what you had to do to be able to dance.
0:53:44 > 0:53:49You have to be able to stand, have strong legs and have explosive power.
0:53:49 > 0:53:52And you had to be able to jump.
0:53:52 > 0:53:57As you've seen, it, basically, is easier to do all of those things the smaller you get.
0:53:57 > 0:54:02The smaller you get, the stronger you get, the higher you can jump and climb.
0:54:02 > 0:54:09It's so incredibly great being small, but the other way round is also true and depressing, isn't it?
0:54:09 > 0:54:14It means the bigger you get, the harder all those things get
0:54:14 > 0:54:17and the harder it's going to be to dance.
0:54:17 > 0:54:21What we thought we'd do is that we'd turn me into an elephant
0:54:21 > 0:54:26to show you exactly how hard it is for a big thing like an elephant to dance.
0:54:26 > 0:54:30Yeah, let me give you my jacket. So made some trousers -
0:54:30 > 0:54:35what the seamstress has done is they've sewed sand into these things,
0:54:35 > 0:54:41so they're not just heavy at the bottom, they're heavy all the way down and they kind of...
0:54:41 > 0:54:44HE LAUGHS
0:54:44 > 0:54:50It's so heavy that I can't actually get up! But let me just try.
0:54:53 > 0:54:54OK, I'm...
0:54:54 > 0:54:58- Right! - APPLAUSE - Thank you.
0:54:58 > 0:55:04Erm...it's actually funny, just standing up in these is exhausting.
0:55:04 > 0:55:10They're so heavy, there's so much weight I'm having to carry and it's quite hard to move your legs,
0:55:10 > 0:55:16erm...but I'm still going to give it a go at dancing
0:55:16 > 0:55:21because maybe even despite all these problems of being big, elephants, maybe they can dance.
0:55:21 > 0:55:23Let's just try it, shall we?
0:55:23 > 0:55:25DISCO MUSIC PLAYS
0:55:25 > 0:55:26- OK.- OK.
0:55:26 > 0:55:29OK, hand on my shoulder.
0:55:29 > 0:55:33- We're going to mambo. Forward the left. Back on the right.- Yes.
0:55:33 > 0:55:36Forward on the left, back on the right!
0:55:36 > 0:55:38Thank you. OK, yes.
0:55:40 > 0:55:41Oh, this one forward!
0:55:45 > 0:55:48I think it's... I'm exhausted!
0:55:54 > 0:55:59- Thanks very much for trying, guys, but I think it's hopeless. - Never mind, thank you!
0:55:59 > 0:56:01See you in a bit.
0:56:01 > 0:56:07All the way through this lecture, it looks like it's really great being small,
0:56:07 > 0:56:12and so maybe you're getting a bit depressed because you're thinking, "Well, I'm too big."
0:56:12 > 0:56:16So I want to end by telling you some good things about being big
0:56:16 > 0:56:24and I want to do that by bringing on Hamish the hamster and Sweep the dog because...
0:56:24 > 0:56:27Here they are. Hamish, did you enjoy the show?
0:56:27 > 0:56:31Yes. Hello, Hamish, how are you doing?
0:56:31 > 0:56:34Now, the thing is that all mammals
0:56:34 > 0:56:37have the same kind of hearts designed the same way,
0:56:37 > 0:56:43so Hamish has got the same kind of heart as me, so has Sweep the dog and even elephants.
0:56:43 > 0:56:48Those hearts will only beat for a certain number of heartbeats until they give up.
0:56:48 > 0:56:51Do you know how many heartbeats that is?
0:56:51 > 0:56:55One billion. That's what you've got. One billion heartbeats.
0:56:55 > 0:57:00That's what Hamish has got, that's what Sweet has got, right?
0:57:00 > 0:57:05So, now. Heartbeats. Let's listen to some heartbeats
0:57:05 > 0:57:08because they're not all the same, are they?
0:57:08 > 0:57:11It actually varies with size. If I listen to Hamish's heartbeat...
0:57:11 > 0:57:13Are you all right, Hamish?
0:57:13 > 0:57:18Let me just do that. Well, it's so fast. It's de-de-de-de-de!
0:57:18 > 0:57:20Really, really fast.
0:57:22 > 0:57:25And now if I listen to Sweep's heartbeat.
0:57:27 > 0:57:30Yeah, it's fast too. Ba-da-ba-da-ba-doo.
0:57:30 > 0:57:33Not as fast, but...
0:57:34 > 0:57:36And my heartbeat is slower still.
0:57:36 > 0:57:39Ba-dum... Yes, calm. No, not really.
0:57:39 > 0:57:44So, that's the funny thing is that the bigger you are, the slower your heart beats
0:57:44 > 0:57:48and the smaller you are, the faster your heart beat.
0:57:48 > 0:57:51But if we all have the same number of heartbeats, which we do,
0:57:51 > 0:57:55that means that smaller things live less long, because they use their heart beats quicker.
0:57:55 > 0:57:58So hamsters live for two years.
0:57:58 > 0:58:01Dogs live for between 10 and 14 years,
0:58:01 > 0:58:06and we, rather triumphantly, live 70, 80, 90 years, which is a great thing to think about.
0:58:06 > 0:58:09So, in a way it all evens up, doesn't it?
0:58:09 > 0:58:15If you're small, you get to jump, be hugely strong, climb up walls, jump off buildings.
0:58:15 > 0:58:21- If you're large, you get to look at all that and live a long life. - LAUGHTER
0:58:21 > 0:58:22So, I hope you've enjoyed this.
0:58:22 > 0:58:28I hope you realise that size does matter. It matters for you and thank you and good night.
0:58:53 > 0:58:54Subtitles by Red Bee Media Ltd