Why Elephants Can't Dance Royal Institution Christmas Lectures


Why Elephants Can't Dance

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CHEERING AND APPLAUSE

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Well...

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Hello, everybody. Hello.

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My name is Mark Miodownik,

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I'm a material scientist from King's College London.

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I'm going to talk you about stuff.

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You're all made of stuff.

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I'm made of stuff, this floor is made of stuff. It's wonderful stuff.

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You think you know something about stuff, don't you?

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I'm going to show you some strange stuff that perhaps you don't know so much about.

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The Royal Institution - such a civilised place!

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A cup of tea before I start my lecture, how wonderful.

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I need some sugar. Let's get some sugar stuff.

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Here it is. Put it in my tea...

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Now, look, even the cup is made of stuff.

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The spoon is made of stuff.

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Stir my cup...

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The thing about stuff is that sometimes it does things that you weren't really expecting...

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A spoon that melts in your tea. Not so useful, maybe, but still incredible, don't you think?

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Now...while we're on incredible,

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I've got a liquid here that's incredible.

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And before I show it to you, I want to ask you all a favour.

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Could you all turn off your common sense for this lecture?

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I need you just to turn it off. I know your mums and dads want you to have it on afterwards,

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but I'll be showing you things so strange, so odd,

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that it'll be a hindrance if you keep saying, "Oh, that doesn't make any sense."

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Turn off your common sense. Now, liquids and mobile phones, they don't really mix, do they?

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Anyone who's ever sat on the loo with their phone in the back pockets and heard a splosh knows this.

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So, you shouldn't do this, should you?

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Right?

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PHONE RINGS

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No problem at all if you've got a strange liquid called a fluorocarbon.

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This stuff doesn't hurt mobile phones at all.

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In fact, mobile phones love it. Still working, fine.

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Don't you think we should put this in all the loos?

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Don't you think? That would save us all a lot of bother.

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So, stuff really can just take you completely unawares.

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Here is a coffee cup set, sent to me by my aunt.

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I was using it for ages until I thought, there's something very odd about this.

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I took it into the lab and we did all sorts of tests on it.

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Nothing came up positive, until we used the Geiger counter on it.

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Now, a Geiger counter detects radioactivity.

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BLEEP

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Now, if I'm radioactive, this will click.

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Phew!

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CLICKING

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It's a very strange present from your aunt, don't you think?

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I've been checking all her presents from then on with a Geiger counter, I can tell you.

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So, how do we understand these strange properties of matter?

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And once we understand them, can we use them to make even more marvellous things?

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Well, in order to understand that, I need to take you on a journey,

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which is going to involve understanding about size.

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And... What does that mean? Well, we're sort of used to the three dimensions of space, aren't we?

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X, Y, Z, left, right, down, back, up.

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You sort of think, if I know where I am in those dimensions, surely I know everything?

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But it turns out not to be true.

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It turns out that even for a whale, or an ant, or a teacup,

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you need to know how big you are if you know how things are going to happen in the world.

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Let me take you on a journey. We're going to be dimension travellers in these lectures.

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I'm going to take you to the really big. I'm going to take you to skyscrapers.

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I'm going to show you that the forces that dominate up there is gravity.

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That's going to really make a big difference to huge things.

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Then, we're going to zoom into small things, atoms,

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and we'll see that different physics dominates down there.

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Quantum mechanics, very strange stuff goes on.

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And despite the fact that it's very small, there's a lot of space down there.

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How weird is that? The key point is going to be that at different scales, different physics dominates.

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So, even though I can stand on a tiny salt crystal,

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it's not gravity that keeping me stuck to it,

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it's the surface forces of this crystal plane.

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It's actually very sticky. Oh!

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In this lecture, what we are going to be doing is looking at animals,

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and how size affects animal behaviour.

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In particular, why it's very useful to be small.

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So, we're going to look at ants to see how they're super-strong.

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And to be honest, when you're shrunk down like this, super-scary!

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And then, we're going to look at the big things - elephants.

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Wonderful, huge creatures, amazing things.

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But it turns out they're not actually relatively very strong.

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And we're going to ask the question, can they really dance?

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So that's the journey we're going to take.

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Now, I've got a pet hamster...

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called Hamish. Has anyone here got a pet at all?

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Have any of you got pets? You have? Shout out their names.

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Cats? Dogs? What have you got?

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-SHOUTING

-Dog? Crocodile?!

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OK, all right. Fantastic. Now...

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..I took my pet hamster on holiday with me.

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I hope you all take your pets on holiday with you. We went to Dubai.

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The reason we went to Dubai - it's very hot there, I wanted to get the sun, so did my hamster -

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is because we wanted to see the tallest building in the world.

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This is the Burj Khalifa, and it is huge.

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It's half a mile high and we went to the top, and this is what happens when you look down.

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It is very scary. Half a mile down.

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That's what it seems. I had my hamster and I said to my hamster, woah, that's a long way down.

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Tell you what, I'll race you to the bottom.

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You go this way, right, and I'll take the lift.

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The funny thing is, that he kind of was up for that.

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He was up for jumping.

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Now, that isn't a very tenable position for a hamster, is it?

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Jumping off a building...

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Or is it? Maybe he knows something that I don't.

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Now, if I fell from this height, I'd certainly die, but could Hamish survive?

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Does size matter when it comes to falling off buildings?

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We really should meet Hamish, don't you think, and see what he's got to say.

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Come and meet Hamish the hamster, and also his friend, the dog Sweep.

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Ah, here's Hamish.

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Hello, Hamish.

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And Sweep. What's your name?

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-Charlotta.

-Charlotta, and you're...?

-Alan.

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Alan, and you've got Sweep and Hamish. Ah, how's he doing?

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How sweet, they're both happy.

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Now, who thinks that Hamish could survive a drop off a tall building? Quite a lot of you.

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And who thinks they have no chance, Hamish has no chance of survival? Who thinks that?

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A few of you. OK, so we're undecided in this audience, aren't we? OK.

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And what about Sweep the dog?

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Who thinks Sweep the dog can survive a large fall off a building?

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-No one does.

-I do!

-Oh, you do! Fantastic! OK, love it.

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OK, great. So, how would we decide this?

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How can we decide if this is true?

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Well, let's do an experiment, right?

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You'll have noticed we've got this large box in this lecture theatre.

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This isn't as tall as a tall building, but it's pretty high.

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So, if we do an experiment dropping pets, we're going to surely find out the answer to this, aren't we?

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Now, of course we're not going to drop real pets. Did you think...?

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Come on!

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I really hope that no one at home either thinks about dropping pets.

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It's really cruel, we'd never do that. We'd never do that.

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We've got some crash-test pets here to take the place of these pets,

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and we're going to do the experiment with these crash-test pets.

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Later, we'll bring you two back on to review the results.

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Is that OK, Hamish? Yeah, you can watch.

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You go back and take your seat, and you too, Sweep, and we'll see what happens.

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All right, so, this is pretty exciting.

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This is Andy. Andy has rigged up this thing and it's a box.

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It's going to take these crash-test pets to the top of this lecture theatre.

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Now, what are these crash-test pets?

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They're balloons filled with jelly, which is ballistic jelly.

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It replicates the flesh of a...

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Well, a bit. All right. So, this is crash-test dog.

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He's ready, isn't he?

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And this is crash-test hamster.

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Oh, he's moving all over the place! They're a bit nervous, fair enough.

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They're going to have a bit of a jump. They're intrepid pets.

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Let's put crash-test hamster up and let's go for this.

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All right, up he goes. You'll notice that they're both the same shape, right?

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And they're both made of the same material.

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So this is a fair comparison.

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Sometimes they don't want to jump,

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they get nervous. You know what it's like at the top of a tall building.

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So, we've got this trap door. And I press this button and crash-test hamster has no choice but to drop.

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It's a bit of a James Bond trick, actually.

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OK, crash-test hamster. Let's do a countdown for him, shall we?

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5, 4, 3,

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2, 1...

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Woah! Let's hear it for the crash-test hamster.

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Yes!

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OK, so crash-test hamster has survived, as most of you thought.

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And now let's just have a look at him.

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How is he feeling? Yes, you're fine, well done.

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Good one. He's all right.

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Bring it on, he's saying. Taller, higher, bigger!

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Crash-test dog's looking a bit nervous now. His turn next.

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Crash-test dog, how are you feeling? Yes, all right, you're a bit quiet.

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Let's get crash-test dog in here.

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How's he feeling? All right.

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Crash-test dog, up he goes.

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I've got a little communication link with crash-test dog.

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Yes, I know, I know. You'll get a bone, yes, yes.

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All right. 5, 4, 3,

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2, 1...

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Oh!

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I think we might need an ambulance... Oh...

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Yeah... I think...

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We're getting the ambulance. OK, fine. The jelly ambulance is coming.

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So crash-test dog is not looking too well from that fall.

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It turns out that essentially, as you guys thought, most of you,

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it does actually matter how big you are, whether you survive a fall.

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So, what's changed? We've got the same material.

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One of them isn't stronger than the other one.

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It's just jelly, and they're both made of jelly. So, what has changed?

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One is bigger than the other.

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What does bigger mean? Let's think about volume.

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It's a funny word isn't it, volume?

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You kind of think of it as liquids, and things you drink.

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But it actually just means how much space you're occupying.

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It is an odd thing. Let's just explore volume for a bit.

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I'm going to need a volunteer for this, OK?

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Yes, would you like to volunteer?

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Yes.

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APPLAUSE

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Hello. What's your name?

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-Annie.

-Annie, do you want to come round here, Annie?

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Here we go. This looks like some weird game.

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It's sort of is, in a way. I hope you're up for this.

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Now, we've got once sphere here, which is empty.

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It's twice as big as these small spheres, which are full of water, coloured water.

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When I said it's twice as big, you didn't stop me there, did you?

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But you probably wanted to say, tell me more, what do you mean by bigger? Right? Good thinking.

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I'll answer that question. It's an excellent question.

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I'm talking about the width. So, the diameter.

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Let me just prove that to you.

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So, this is seven and a half in width,

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diameter. And this is 15.

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Right, so... Across there, it's double.

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The question to you, and this is difficult, because you're under the cameras,

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I'm going to ask you how many of these we had to pour into that one,

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which is twice the diameter, would we have to pour in in order to fill this up to the top?

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Ie, what's the ratio of the volumes? Now, I'm going to give you two seconds to think about this.

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I'm going to ask the audience to think about this too,

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but not to shout it out, but to do calculation in your heads.

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Because you all know the formula for the volume of a sphere, don't you?

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4/3 Pi r cubed.

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All right, you guys do the calculation, and we'll do the experiment.

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-Go on then. How many do you think?

-Eight.

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-Eight? Are you sure?

-Yes.

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Oh! Do you think she's right? Who thinks that that is way too many?

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Quite a lot of you. And who thinks it's too few?

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And it's a trick that we've only put nine here? Some of you? Nice. Would we do that?

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Maybe we would. Let's go. Have a go.

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You think eight.

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That's one... Although this isn't going up very fast.

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That's two.

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All right, that's three.

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Four. It's looking good for you, isn't it.

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That's five. And you're getting nervous...

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A little bit. That's six.

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This is seven.

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Here we go. Oh...

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Now, the question is, will it be eight, and are you going to be victorious?

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And if you are, are you going to run up the stairs shouting, "Yippee"?

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Yes!

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You! You!

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Thank you very much for that.

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Do have a seat again.

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So, it's quite surprising, don't you think?

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You increase something twice, the width or diameter twice,

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and your volume increases by eight times.

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Oh, crash-test dog is back!

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He's bandaged up. He survived.

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The show must go on, mustn't it.

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How are you feeling? Oh, not too talkative.

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Fair enough. So, how does this all relate to crash-test dog and crash-test hamster? Well...

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they're different sizes, so how different in sizes are they?

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Well... Crash-test hamster is about five and a bit.

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And crash-test dog is about 25 and a bit.

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Crash-test dog is five times bigger than crash-test hamster.

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If you do the maths in your head - are you doing it up there now?

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It turns out that crash-test dog is 100 times bigger volume than crash-test hamster.

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100 times.

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OK, so that would mean, if that's true, that would mean that

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crash-test dog is 100 times heavier than crash-test hamster.

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Force of gravity on it's going to be 100 times heavier.

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Do you guys believe me on that one?

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Do you think that's at all believable?

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100 times heavier?

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Well, I've got some scales here.

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Let's just have a look at that.

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Let's measure it.

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Crash-test hamster is about 100 grams.

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Crash-test dog, even injured, with his bandage,

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so it's a bit unfair cos he's got a bit more weight,

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just over 10 kilos.

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Crash-test dog is slightly more than 100 times bigger than crash-test hamster.

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Sorry, 100 times heavier. Does that answer our question,

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why crash-test dog had such a hard time when he hit the floor?

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Because he was 100 times heavier he had 100 times more force hurtling him down to the floor.

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It's not the whole story, because when you hit the floor,

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you can basically spread your weight and the force of impact over a large area.

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So, the pressure on every part of you would be reduced, OK.

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So, it's not just how much force you hit the floor with,

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it's how much you can spread it out.

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That's about area, isn't it, this kind of thing called area.

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We really want to know whether crash-test dog is 100 times bigger area,

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whether the outside of crash-test dog is 100 times bigger area

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than crash-test hamster, don't we?

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That's what we really want to know. What we did earlier, we scanned in,

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with a 3D scanner, these two animals,

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and we worked out their area. We've got them here.

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Surface area of crash-test hamster is 100.

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Surface area of crash-test dog is 2,800.

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That's a bit concern-making now.

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Now we're starting to get worried for crash-test dog.

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Too late, I know what you're saying.

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The area over which it could spread that force has only gone up

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by essentially 28 times, but the weight has gone up by 100 times.

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This tells you something really fundamental about making things bigger.

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It's that the area to volume ratio changes when you get bigger.

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So, as you get bigger, it turns out that your area doesn't keep up with your volume.

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You get more inside and you get less and less outside proportionally.

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That really means that when you hit the ground,

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you've got less area to spread that force over. We have an action replay.

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I know you've all been waiting for this action replay, of the rather unfortunate accident that happened.

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This is crash-test hamster coming down and spreads its weight over a large area and survives.

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We knew it survived.

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It was OK. Now we go to crash-test dog.

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What happens is, crash-test dog comes down, tries to spread.

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It got 100 times more force,

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but it's only got 28 times more area, and basically

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the pressure on all its extremities

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couldn't cope and it split, but luckily we could rebuild him and he seems to be on the mend.

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So, there it is.

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It turns out one of the reasons why it gets easier for you to survive a fall when you're smaller,

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because you've got a lot of area and not very much volume.

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So, your surface area to volume ratio is very high.

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There's something else that helps you too.

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Because we've kind of gone on the assumption that they hit the floor at the same speed, but did they?

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Things don't always fall at the same speed.

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I want to just show you something about that, here, with this demo.

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I've got a snowflake

0:19:190:19:21

and I've got a snowball.

0:19:210:19:24

Well, they're not really snow, but they represent them.

0:19:240:19:29

They're exactly the same weight, but they won't fall...

0:19:290:19:35

Well, let's see. Will they fall at the same speed?

0:19:350:19:38

OK... No, they won't. So, that's interesting because

0:19:380:19:41

basically, they have the same force pushing them down, pulling them down, of gravity,

0:19:410:19:47

because they've got the same weight.

0:19:470:19:49

But this one has more area, so it has more air resistance.

0:19:490:19:52

So, if you think about that with regards to small hamsters,

0:19:520:19:57

not only when they hit the ground do they have more area to spread it over,

0:19:570:20:02

when they come down, they slow down quicker because their surface to volume ratio is really good.

0:20:020:20:07

We know this. Snow falls very gently.

0:20:070:20:11

If you take the same volume of liquid and you make it

0:20:110:20:14

into a drop of rain, it hits quite hard actually.

0:20:140:20:17

It hits the top of my head very hard, I can tell you!

0:20:170:20:20

That's the price you pay for being a bit bald.

0:20:200:20:22

Let's not go into that, thanks for bringing it up.

0:20:220:20:25

So, we know the rules now.

0:20:250:20:29

The rules of falling are that surface to volume ratio is king. You really need to know this.

0:20:290:20:35

If I, instead of hamster, was jumping off the tallest building, if it was me,

0:20:350:20:40

then I could manipulate the rules maybe.

0:20:400:20:43

Let's say I jump off the building.

0:20:430:20:46

I'm falling through the air,

0:20:460:20:50

and then I realise that I haven't got a big enough surface to volume ratio.

0:20:500:20:54

Doesn't that always happen after you jump?!

0:20:540:20:58

So, I think, Hamish!

0:20:580:21:00

Chuck me the umbrella! Thanks.

0:21:000:21:02

Hamish chucks me the umbrella, and now I've increased my area.

0:21:020:21:07

So, I'm going to slow down,

0:21:070:21:10

and I fall much slower.

0:21:100:21:12

I basically am cheating. I am increasing my area artificially.

0:21:120:21:16

This, of course, is the essence of a parachute.

0:21:160:21:20

So, parachutes work because they change...

0:21:200:21:22

You cheat, you change your surface to area ratio.

0:21:220:21:24

You add a lot of area, and don't really change your weight very much, or volume very much.

0:21:240:21:29

So, that's really cool.

0:21:290:21:30

When you're parachuting, what you're doing is becoming a hamster.

0:21:300:21:34

OK? Parachutists don't talk about it like that.

0:21:340:21:38

It's much more of a gung-ho sport.

0:21:380:21:40

But that's really what's happening.

0:21:400:21:43

So, it's not just actually that it helps you jump off buildings,

0:21:430:21:47

this ratio, and survive falls.

0:21:470:21:50

It's really important in your whole life.

0:21:500:21:52

How many of you are fed up with people saying to you, "Oh God, you've grown!"?

0:21:520:21:57

Or, "How tall are you now?" You're like, ugh!

0:21:570:22:00

Why are you obsessed with my height?

0:22:000:22:02

Ugh! That kind of thing. People constantly measuring your height...

0:22:020:22:07

Next time, I've got a good line for you guys.

0:22:070:22:09

Just say, "Don't worry about my height. It's my surface to volume ratio you should worry about."

0:22:090:22:14

When I was a kid, I used to go to the swimming pool with my brothers, who are all bigger than me.

0:22:140:22:19

I used to start shivering about 10 minutes in, freezing cold. I went blue with cold.

0:22:190:22:24

And they were totally fine, swimming around for hours.

0:22:240:22:27

I always used to think, they're so much stronger, tougher than me.

0:22:270:22:31

But actually, they just had a lower surface to volume ratio.

0:22:310:22:35

So, your area is what cools you, as a person, so that you evaporate water off you.

0:22:350:22:41

It's your volume that gives you the warmth, the blood, and all those kind of things.

0:22:410:22:45

If you haven't got very much volume, but a lot of area, you'll cool down fast.

0:22:450:22:49

So you're going to shiver.

0:22:490:22:51

So the bigger you get, the less cold you'll get in swimming pools. This is also true of babies.

0:22:510:22:57

People are always dressing up babies with 10 coats, and you're like, don't mollycoddle them.

0:22:570:23:02

But they've got a terrible surface to volume ratio when it comes to cold.

0:23:020:23:06

You really do need to put coats on them.

0:23:060:23:09

So, that's us manipulating surface to volume ratio.

0:23:090:23:12

But could we find examples

0:23:120:23:15

of nature manipulating it in other ways?

0:23:150:23:18

We found one the other day when I was on holiday.

0:23:180:23:22

I was looking at the ceiling

0:23:220:23:24

in Dubai, and this gecko was walking across the ceiling.

0:23:240:23:29

I was thinking, how can it do that?

0:23:290:23:31

That's really mad.

0:23:310:23:33

And so,

0:23:330:23:35

I kind of went home and I started doing some research about how geckos can stick on the ceiling.

0:23:350:23:41

Hello. We've got a gecko with us, haven't we?

0:23:410:23:44

-Yes.

-Gordon Gecko.

0:23:440:23:45

He's in there, isn't he? And what kind of gecko is he?

0:23:450:23:48

He's a Tokay gecko, the largest type you can get.

0:23:480:23:51

-OK, brilliant. He is able to walk up walls, isn't he?

-He is indeed.

0:23:510:23:56

Pretty amazing, isn't it? We've a guest who can walk up walls, everybody! Can we have a look?

0:23:560:24:01

-Would he have a go?

-Yeah, sure.

-Will he be camera shy?

0:24:010:24:03

I'll give him a go.

0:24:030:24:07

Might be a bit noisy.

0:24:070:24:08

There he goes. He looks a bit annoyed.

0:24:110:24:14

-Is he a bit annoyed?

-He's all right.

0:24:140:24:17

They do have a bit of a temper on them.

0:24:170:24:19

Is it because he hasn't eaten or something?

0:24:190:24:21

-No, he's all right.

-He's been eating, OK.

0:24:210:24:23

-Because I get a bit annoyed. Anyway...

-Ready?

0:24:230:24:27

There he is! Look at that!

0:24:270:24:29

APPLAUSE

0:24:290:24:33

Now, how on earth does he do that?

0:24:400:24:42

That is so brilliant. Well done. That is so amazing.

0:24:420:24:46

Now, you hang on there. Will he be all right?

0:24:460:24:48

-Can we just leave him there?

-Yes.

0:24:480:24:50

Amazing. Isn't it amazing? So let's think about how a gecko can do this.

0:24:500:24:55

I was thinking in my hotel room,

0:24:550:24:57

I was having a word with Hamish the hamster,

0:24:570:25:00

and we came up with four possible explanations.

0:25:000:25:03

I'll run him past you, then we'll do a vote.

0:25:030:25:05

So you guys can run with me on this one.

0:25:050:25:08

We thought that it may be

0:25:080:25:10

that geckos have some sort of glue on their paws.

0:25:100:25:14

A bit like a spider squirting out glue,

0:25:140:25:17

and that's how they can walk up walls.

0:25:170:25:20

So that is option number one for you to think about.

0:25:200:25:23

Option number two is that they actually have nails.

0:25:240:25:28

Well, not nails, but something spiky, all right?

0:25:280:25:32

And that's how they get up these walls.

0:25:320:25:34

-Is he all right?

-Yeah, he's fine.

0:25:340:25:37

I'm talking about you, gecko.

0:25:370:25:40

Yes, yes!

0:25:400:25:41

Option number three is that - and this is my favourite -

0:25:430:25:47

that they have little suckers on them,

0:25:470:25:49

like the stuff you put onto bathrooms and things like that.

0:25:490:25:53

Suckers, impressed? Well, all right.

0:25:530:25:56

And option number four, they have some sort of weird hairs on them, weird kind of hairs.

0:25:560:26:01

We ran out of ideas by that point! OK, weird hairs.

0:26:010:26:05

Let's have a vote. Who thinks it is bits of glue, a bit like a spider squirting out glue. Anyone?

0:26:050:26:11

Who votes for that? Oh, no-one.

0:26:110:26:14

Who votes for the nails.

0:26:140:26:17

Come on! It was quite a good idea.

0:26:170:26:19

No?

0:26:190:26:20

Who votes for suckers?

0:26:200:26:24

Suckers!

0:26:240:26:25

Maybe, maybe. I'm not giving anything away.

0:26:250:26:29

And who votes for the hairs?

0:26:290:26:31

So we're sort of equally split in this audience between hairs and suckers.

0:26:310:26:35

Not often you get to say that, is it?

0:26:350:26:37

So, Gordon, do you want to tell us how you do it? No, you don't. All right.

0:26:370:26:42

All right, so... let's see how he does it.

0:26:440:26:48

Let's have a look under the microscope.

0:26:480:26:51

We found a microscopic image of the paws of a gecko and we've got it over here.

0:26:510:26:56

When you actually look under the microscope at these paws of the gecko,

0:26:560:27:01

this is really high magnification,

0:27:010:27:04

you get this thing, it looks a bit like celery, or rhubarb.

0:27:040:27:08

Now if you zoom even further in... Yes, look, hairs!

0:27:080:27:11

Actually hairs on the end of hairs.

0:27:110:27:13

It's hairs on hairs

0:27:130:27:16

is what this gecko's paws are under the microscope.

0:27:160:27:19

This gecko has hairy hands.

0:27:190:27:21

However ludicrous that sounded, it is the truth.

0:27:210:27:25

So that's really mad, isn't it?

0:27:250:27:27

OK, well, look....before we go on,

0:27:280:27:31

I'm just going to let Gordon go, because he looks like

0:27:310:27:35

he's kind of, yeah, he wants to have a bit of a rest, doesn't he?

0:27:350:27:39

Thank you very much.

0:27:470:27:48

Geckos climb up walls using hairy hands.

0:27:500:27:54

That hasn't told us anything, has it? That's HOW it works, but why does that work?

0:27:540:28:00

What's going on there?

0:28:000:28:03

So I want to do a demo now, which is going to try and...

0:28:030:28:07

eke that out. What's really going on here?

0:28:070:28:09

I'm going to need six - can you believe it? - I need six volunteers.

0:28:090:28:13

I need three boys, the strongest boys in the world, and three girls, the strongest girls in the world.

0:28:130:28:18

OK, so, boy there - yes. And, go on,

0:28:180:28:23

the dog denier.

0:28:230:28:25

That girl there, yes, yes, you. Yes!

0:28:270:28:31

OK. Girl power versus boy power.

0:28:310:28:35

Now, what we've got here is two health and safety manuals.

0:28:350:28:39

If I send that... You can hold that rope, and you guys hold that rope.

0:28:420:28:47

Have you got a bit of the rope? You need to go in a line.

0:28:470:28:49

You're going to pull against each other. Are you ready?

0:28:490:28:53

Two health and safety manuals.

0:28:530:28:55

All we've done with them is interleave the pages.

0:28:550:28:58

There's no glue, no bolts. Just inter-leave the pages.

0:28:580:29:03

What I want you to do is rip these apart. All right?

0:29:030:29:07

In doing so, you guys humiliate the boys by pulling them across here.

0:29:070:29:13

You guys, you know, girl power, boy power.

0:29:130:29:17

Right, ready? Are you guys ready?

0:29:170:29:19

Steady... Go!

0:29:190:29:21

Yes! And the girls are really holding on!

0:29:210:29:23

What's happening to this?

0:29:230:29:26

What is happening to this? Come on!

0:29:260:29:28

Yes!

0:29:280:29:29

SHOUTING AND CHEERING

0:29:290:29:31

OK, OK. Wow, that's a dead heat, I think.

0:29:380:29:42

Well done, guys.

0:29:420:29:44

What also won here was these books.

0:29:440:29:48

Yes, I know. Are you all right?

0:29:480:29:52

-They always win.

-Yes, they always win. You have to get used to that.

0:29:520:29:55

Now, look, do you believe me that there's no glue here?

0:29:550:29:59

HE BLOWS

0:30:000:30:04

Have a look at that. Look at that.

0:30:110:30:13

OK?

0:30:150:30:16

That's mad, isn't it?

0:30:190:30:21

No glue, right? Just paper, no glue?

0:30:210:30:24

-No.

-So, that's incredible, isn't it?

0:30:240:30:26

It turns out that even though you guys are really strong,

0:30:260:30:29

you'd need two tanks pulling in opposite directions to pull this apart.

0:30:290:30:33

Amazing, isn't it? Well, thanks a lot.

0:30:330:30:36

You can go back to your seats. Thanks, guys.

0:30:360:30:38

Next time you're in a burning building and you're thinking there's no way out

0:30:450:30:49

and you start going for the sheets and knotting them together, don't do it.

0:30:490:30:53

Get the telephone directories, all right?

0:30:530:30:56

So, look, how does that work and how can that help us understand the gecko?

0:30:590:31:06

Why is it such a strong force?

0:31:060:31:08

Well, it turns out that what's keeping those pieces of paper together

0:31:080:31:13

is tiny molecular forces between the two sheets.

0:31:130:31:16

And the forces are very small, but if you maximise them over lots of area,

0:31:160:31:22

so if you can times a small force by a large area you get a decent force

0:31:220:31:26

and by having every single piece of paper over each other

0:31:260:31:29

we actually managed to get a large area of interface there, didn't we?

0:31:290:31:32

So...could it be that the gecko is using the same idea to climb up walls?

0:31:320:31:39

Well, what does a wall look like when it's magnified up?

0:31:390:31:43

This is not a picture of the Alps, but it might be, right?

0:31:430:31:46

This is what happens if you magnify a wall.

0:31:460:31:49

It made look smooth to you, and you may run your finger across a wall

0:31:490:31:53

or a surface and think that's quite smooth.

0:31:530:31:55

But under the microscope, surfaces are very rough.

0:31:550:32:00

They look like mountains, right?

0:32:000:32:02

So, if you're touching something...

0:32:040:32:06

So, this is a massive me.

0:32:060:32:08

This is what my thumb looks like. See, quite nicely groomed!

0:32:080:32:12

And if I'm touching the wall and I'm trying to climb up it,

0:32:120:32:16

if I want to use the same force as with the book demo,

0:32:160:32:19

I need to maximise my area of contact, so I try to do that.

0:32:190:32:23

I'm pressing my finger in here, but you can see that, actually, all I ever do is

0:32:230:32:29

just touch the tips of the mountain

0:32:290:32:32

and it's really very hard for me to do anything else and so, ultimately,

0:32:320:32:37

I get very little contact with the wall in terms of area,

0:32:370:32:41

and so I don't get any kind of help.

0:32:410:32:43

And, you know, this is also true of when you touch anything.

0:32:430:32:48

You touch a surface and you think you're touching it, you're mostly just touching the tips of mountains.

0:32:480:32:53

We very rarely really touch things, but the gecko knows better.

0:32:530:32:57

The gecko has hairy hands, so if you were to zoom in on a gecko's paw,

0:32:570:33:01

we've already seen that, he's got these amazing hairs, so look what the gecko does.

0:33:010:33:07

The gecko gets onto the wall, the wall is rough, but that's no problem

0:33:070:33:12

because the hairs get right down into the valleys, right?

0:33:120:33:17

They are maximising an area of contact there,

0:33:170:33:20

so even though there's no adhesive force in terms of glue

0:33:200:33:23

or any kind of mechanical scratching, it's just the same force,

0:33:230:33:26

these surface forces, which are tiny,

0:33:260:33:29

but you maximise the area of contact and you can climb up walls.

0:33:290:33:33

So well done, gecko, for working that one out.

0:33:330:33:35

That's pretty impressive!

0:33:350:33:36

I know what you're thinking. You're thinking, you material scientists,

0:33:440:33:48

why don't you make some gloves like a gecko's hand, hairy gloves,

0:33:480:33:51

then we can all just walk up walls and be Spiderman, right?

0:33:510:33:54

I know what you're thinking. Well, it's not so far from the truth.

0:33:540:33:58

I've got here the latest sample from a lab in California

0:33:580:34:02

which is trying to do exactly that.

0:34:020:34:04

It's just a prototype at the moment. I'll show you what it looks like under the microscope.

0:34:040:34:09

If we go here and we look in...

0:34:090:34:11

what they've done is engineered a material that has these filaments,

0:34:110:34:16

and when they're pressed against the wall, they bend and they make huge contact with that wall.

0:34:160:34:21

It just feels very smooth and flat, but you can just

0:34:210:34:26

stick things onto it.

0:34:260:34:28

Oh! It's a prototype, OK?

0:34:290:34:32

No, it does work, actually.

0:34:320:34:35

There it is. Yes!

0:34:350:34:36

So, actually the future could be that we have these amazing gloves,

0:34:360:34:40

but there is one problem with that future, and I want to show you that problem with that future

0:34:400:34:45

with this enormous piece of Blu-Tack, because this stuff, you know, right?

0:34:450:34:52

And you're thinking Blu-Tack, yawn. But it's actually

0:34:520:34:55

as sophisticated as the gecko's foot because it works in the same way.

0:34:550:34:59

You take a small piece of Blu-Tack, and this stuff is not sticky, it's not got adhesive in it, has it?

0:34:590:35:04

You could infinitely reuse this stuff.

0:35:040:35:07

It's not like a piece of Sellotape or sticky tape where actually after a while it loses its stick.

0:35:070:35:13

So, how does that work? Well, it's the same as the gecko's foot.

0:35:130:35:16

It's a material that becomes liquid when you put pressure on it

0:35:160:35:21

and that liquid flows into the mountains,

0:35:210:35:24

the rough mountains of this surface,

0:35:240:35:26

and then it maximises the area of contact,

0:35:260:35:29

uses the same adhesive forces, these weak surface forces, and sticks.

0:35:290:35:33

You use this all the time and it's the same as a gecko's foot. So, that's fantastic!

0:35:330:35:39

And then you think, well, OK, I'm just going to go home and I'm going to just cover myself in Blu-Tack.

0:35:390:35:45

I know you guys!

0:35:450:35:47

But don't do it, because from what you've learned tonight

0:35:470:35:50

you already know there's a problem.

0:35:500:35:52

Which is that although the adhesive force goes up,

0:35:520:35:55

if your volume isn't matching that force,

0:35:550:36:00

if your volume's going up quicker, then it's going to override it.

0:36:000:36:03

So if you try and stick this whole piece of Blu-Tack...

0:36:030:36:06

I'm putting pressure on it, doing all the adhesive stuff, but this volume is very large, isn't it?

0:36:060:36:11

So the force downwards is too big for that adhesive force.

0:36:110:36:14

OK, so it's not an accident that geckos are small,

0:36:140:36:19

because they've got low weight and it's all about this ratio, this surface to volume ratio.

0:36:190:36:23

So we need something even better than geckos in order for us to be like Spiderman.

0:36:230:36:28

But it think we can do it, it's just a matter of time.

0:36:280:36:31

OK, so, fantastic!

0:36:310:36:34

Surface to volume ratio - and I know I keep going on about it -

0:36:340:36:38

but it really is absolutely crucial to your life and no more so than this demo is going to show you.

0:36:380:36:43

Under this here I've got a model and it's a model of my lungs, OK?

0:36:450:36:51

This are what my lungs looked like.

0:36:510:36:54

I'm going to put it exactly...

0:36:540:36:55

There we go. No, there we go!

0:36:550:36:59

Now, I'm breathing in,

0:36:590:37:00

and these lungs are exactly the right size for me,

0:37:000:37:03

so air is coming into these lungs.

0:37:030:37:05

Now, would you believe that this is big enough? Probably not.

0:37:050:37:08

When you're breathing in now, you're breathing a large volume of air, so if we all breathe in now

0:37:080:37:13

we're all breathing stuff into this kind of structure.

0:37:130:37:16

Now, at that moment... Breathe out everyone, I don't want you fainting!

0:37:160:37:19

At that moment you breathe in,

0:37:190:37:23

your body has to extract all the oxygen it needs to be alive, right?

0:37:230:37:27

So it's taking oxygen from a large volume

0:37:270:37:29

and it has to get into the blood vessels, which is a large area.

0:37:290:37:33

So, basically, it has to find a way of interfacing that large volume of air into all the blood vessels.

0:37:330:37:38

It does this by making these tiny sacs, these alveolar sacs,

0:37:380:37:42

and it spreads them all out in a kind of filigree way

0:37:420:37:46

and it's just like with the hamster, as you get smaller, these little sacs are like spheres.

0:37:460:37:50

As they get smaller, their area in proportion to their volume gets larger and larger.

0:37:500:37:55

That's exactly what you want.

0:37:550:37:56

You want a large area to interface with the oxygen, right?

0:37:560:38:00

To get the oxygen into your blood and get the carbon dioxide out.

0:38:000:38:03

So, your own body is using the surface to volume ratio to actually just let you live!

0:38:030:38:09

And I want to show you how big this area is that you need to live

0:38:090:38:13

because you can't really see it here

0:38:130:38:15

because you're seeing it as a volume, right?

0:38:150:38:18

But if you spread all these out on to a sheet, how big would that sheet be?

0:38:180:38:22

Well, let me show you how big that sheet would be.

0:38:220:38:25

OK, we've got it here.

0:38:250:38:27

Right, I'm going to take this up, am I? Yes.

0:38:270:38:31

I'm going to, basically, spread this sheet out.

0:38:310:38:34

This piece of silk is the same area as my lungs.

0:38:340:38:36

Would you believe it? It's just inconceivable, isn't it,

0:38:360:38:40

that all this area could be inside your body.

0:38:400:38:42

I want you to pass this around. Is that possible?

0:38:420:38:45

Yes! It's quite nice being in my lungs, isn't it? Keep going, guys. Keep going.

0:38:450:38:49

Right, you guys let go. Let it go.

0:38:490:38:53

My lungs, ladies and gentlemen. There's a small hole.

0:38:530:38:57

Can any of you spot the small hole? That's where I used to smoke.

0:38:570:39:00

Essentially, that is what happens when you smoke -

0:39:000:39:03

your lung area gets smaller and smaller, so you get out of breath.

0:39:030:39:06

So, if you get out of breath and you have lung disease,

0:39:060:39:09

you get a smaller area in which to absorb oxygen, and that's the problem.

0:39:090:39:13

Maximising your area of your lungs is incredibly important to you.

0:39:130:39:18

So, this whole thing is incredible.

0:39:180:39:20

The surface to volume ratio, right?

0:39:200:39:22

The area to volume ratio is so important to you. It can help you survive jumping off a building.

0:39:220:39:29

It can help geckos climb up walls.

0:39:290:39:32

It can do all sorts of things. It's integral to how you breathe and live,

0:39:320:39:36

but it does something even more important than that.

0:39:360:39:39

It can determine whether you can dance or not.

0:39:390:39:42

Whoa!

0:40:170:40:19

The dancers from Strictly Come Dancing! You're from Strictly Come Dancing, aren't you?

0:40:270:40:31

-We're the choreographers of the show, yes.

-What are you names?

0:40:310:40:34

Chris Marquez, Jaclyn Spencer.

0:40:340:40:36

Fantastic. You dance so brilliantly.

0:40:360:40:39

I'm so envious. And, in fact, I made some notes and...

0:40:390:40:44

I just wanted to run these past you because I've come up with three rules having watched you

0:40:440:40:49

about what you need to be able to do to dance.

0:40:490:40:52

-You can critique them and see if I'm on the right track.

-All right.

0:40:520:40:56

Is that OK? So, one of the rules of being able to dance is just to be able to stand.

0:40:560:41:00

You're standing now and if you couldn't, it would be difficult. So it seems a prerequisite.

0:41:000:41:04

-Yeah.

-You've got to be able to stand.

0:41:040:41:05

Then I noticed that you were jumping from foot to foot and there was kind of jigging around

0:41:050:41:11

and that seems to need a lot of strength in your legs.

0:41:110:41:13

Yeah, you need to be able to move your weight.

0:41:130:41:15

-Weight transfer in general is very important, obviously, to dancing, yes.

-Yes, OK.

0:41:150:41:20

And you had to be strong enough to pick up your partner, so that's also weight on the legs.

0:41:200:41:25

-It all goes through here.

-Again, the legs, but often you find that the whole tone in the body.

0:41:250:41:28

So, standing up, strength, jumping.

0:41:280:41:30

If I can do those things, I can dance.

0:41:300:41:33

Well, yes, with a bit of rhythm and...

0:41:330:41:36

I'm going to work on those rules for a bit now

0:41:360:41:39

-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.

0:41:390:41:46

-Ten.

-Ten.

-Ten.

-Bring it on!

0:41:460:41:48

OK, so...

0:41:540:41:57

Now, look, standing!

0:41:570:42:00

That doesn't seem too hard, does it?

0:42:000:42:02

But is it? Is it as simple as that?

0:42:020:42:05

I'm back to spherical animals because, basically, if you ask

0:42:050:42:09

a physicist to do anything they'll end up starting with a sphere.

0:42:090:42:12

So, my model for an animal is a sphere, but this time legs.

0:42:120:42:16

That's a step forward, literally!

0:42:160:42:17

So, now, I've got a spherical animal and all of its weight

0:42:170:42:22

has got to go through its legs, OK?

0:42:220:42:24

So that means that these legs are like the pillars of a building, right?

0:42:240:42:29

All of the force is coming through them.

0:42:290:42:31

So, the area, that cross sectional area of those legs, is what's taking all the weight through there.

0:42:310:42:37

So if that's small, then there might not be enough...

0:42:370:42:40

They've got to be strong enough to support the whole weight.

0:42:400:42:43

If I take this animal, all its weight is going through its legs and it's standing on its own feet.

0:42:430:42:48

It's got four legs, fantastic.

0:42:480:42:50

What happens when I size it up -

0:42:500:42:52

I scale it up and increase its width by two.

0:42:520:42:55

So, this is an animal exactly twice as big in proportions,

0:42:550:42:59

so that means, as we know, that its volume has increased by eight times.

0:42:590:43:03

So, that means its weight has increased by eight times.

0:43:030:43:07

That would be fine if the area of its legs

0:43:070:43:10

had increased by eight times -

0:43:100:43:12

then it would be exactly the same, but has the area of its legs increased?

0:43:120:43:16

-What do you think?

-No.

0:43:160:43:18

No, it hasn't, because this area, this cross-sectional area, has only got four times bigger

0:43:180:43:24

because of this whole problem of when you size things up the surface to area ratio changes.

0:43:240:43:28

So, every one of the legs of this animal, has twice as much force

0:43:280:43:33

running through it and that means that...

0:43:330:43:37

it can't actually stand up.

0:43:370:43:39

So, the thing is, you can't just keep getting bigger

0:43:390:43:44

as an animal and not change your design because sooner or later

0:43:440:43:47

you will collapse under your own weight.

0:43:470:43:49

Now, you don't think that this happens,

0:43:490:43:52

but actually this is what happens with elephants.

0:43:520:43:56

This is an elephant's leg of a juvenile from India.

0:43:560:44:00

It's about six or seven years old and you can already see,

0:44:000:44:05

and we know this, don't we, that the ratios of the bones

0:44:050:44:08

and the thickness of the bones have changed because this is the way out of the problem.

0:44:080:44:13

If you change the ratios, if you make thicker legs,

0:44:130:44:16

then you can support bigger weights and that's what elephants do.

0:44:160:44:19

They make their bones bigger, they make their legs bigger

0:44:190:44:24

because they actually are in trouble if they don't do that.

0:44:240:44:27

Galileo recognised this very early on and people have noticed this ever since and, in fact, if you look at

0:44:270:44:33

elephants you can immediately see it - proportionally they have much thicker legs and they need it,

0:44:330:44:40

otherwise they start to get into trouble with their ability to hold up their legs.

0:44:400:44:44

And if you look at even bigger things like dinosaurs, they have really fat legs.

0:44:440:44:49

And it's not a style choice, OK?

0:44:490:44:52

What's the problem with having bigger, thicker legs?

0:44:520:44:55

Surely that should make them stronger?

0:44:550:44:57

We thought if we're going to talk about this,

0:44:570:45:00

let's get the strongest person we know and ask them.

0:45:000:45:02

And here he is. This is the strongest person I know, and he is strong! Hello.

0:45:020:45:09

CHEERING AND APPLAUSE

0:45:090:45:12

-So, what's your name?

-My name is Terry Hollands.

0:45:150:45:18

And what are your strength credentials, just so we can all...

0:45:180:45:21

I've been England's strongest man, UK's strongest man,

0:45:210:45:24

Britain's strongest man and a five time finalist at World's strongest man.

0:45:240:45:28

CHEERING AND APPLAUSE

0:45:280:45:30

So, you say that...

0:45:370:45:40

-but could you just give us a demonstration of exactly how strong you are?

-Yeah, sure.

0:45:400:45:45

I lifted these weights earlier...

0:45:450:45:48

LAUGHTER

0:45:480:45:49

I just thought, well, as a test, I might see if you can lift them, too.

0:45:490:45:52

Yeah.

0:45:520:45:54

-Do you think you could have a go at that?

-Yeah, sure.

0:45:540:45:57

DRUM ROLL

0:46:040:46:06

Whoa!

0:46:100:46:12

CHEERING AND APPLAUSE

0:46:120:46:14

Did you see the bar bending?

0:46:250:46:28

-That bar, which is about an inch thick steel, bent.

-Yeah.

0:46:280:46:31

That's absolutely amazing.

0:46:310:46:33

I'm so impressed. I want to just get a feel for how much that is compared to your weight.

0:46:330:46:39

Do you mind asking how heavy you are?

0:46:390:46:42

Sure, I'm 180 kilos.

0:46:420:46:43

You're 180 kilos and what did you just lift here?

0:46:430:46:47

-That's 380 kilos.

-380 kilos, so that means that you lifted a bit more than twice your own weight.

-Yeah.

0:46:470:46:54

-That's like a small car, isn't it?

-Yeah, pretty much a small car.

0:46:540:46:58

-Could you lift a small car?

-Yeah, yeah.

0:46:580:47:00

Wow!

0:47:020:47:03

So, basically, you have been able to lift twice your own weight,

0:47:120:47:16

is there anyone who can lift, let's say, five times their own weight?

0:47:160:47:21

Maybe not five times but some of the lighter guys...

0:47:210:47:24

Generally, the bigger you are, the less number of times you can lift your own body weight, basically.

0:47:240:47:30

The lighter guys would be lifting three, maybe three and a half times their weight.

0:47:300:47:34

-The heavier guys would be just over two.

-Absolutely fascinating.

0:47:340:47:37

-I'm so happy that you could come on the show and thank you very much for showing us all.

-Great.

0:47:370:47:43

Thank you very much.

0:47:430:47:45

Wow! OK, so, that was very interesting there, right?

0:47:450:47:48

If you want to be able to be strong per weight, right, if you want to be

0:47:480:47:53

able to lift many times your own weight, well, it turns out you need to be small and we've got

0:47:530:47:59

the world champions at this and they turn out to be very small and I'd like to introduce you.

0:47:590:48:05

-What's your name, sorry?

-My name is Karen Wall.

0:48:050:48:08

-I'm a PhD student at Cambridge University at the moment.

-Welcome.

0:48:080:48:12

And I do actually study how ants manage to

0:48:120:48:16

carry large loads.

0:48:160:48:19

Right, so it's ants who are the world champions at lifting many times their own weight.

0:48:190:48:24

Now, just talk us through this. So what kind of ants are these?

0:48:240:48:27

-So these are basically the leaf cutting ants.

-Look at this one!

0:48:270:48:31

-Look at that!

-Yeah, it's amazing.

0:48:310:48:33

He's showing off, isn't he?

0:48:330:48:34

-He is showing off, yeah.

-He knows the cameras are on, doesn't he?

0:48:340:48:39

Are they going to mind if we pick them up? Are they going to get annoyed? If I was carrying

0:48:390:48:43

my sofa up some stairs...

0:48:430:48:45

He might drop it but he might be all right with it. Let's see.

0:48:450:48:48

If some giant picked me up just to weigh me...

0:48:480:48:51

All right.

0:48:510:48:53

Brilliant, OK. Nice one.

0:48:530:48:55

He doesn't look too annoyed.

0:48:550:48:57

He's still got his sofa.

0:48:570:48:59

So now we have 20.5 milligrams.

0:48:590:49:05

OK, 20.5 milligrams together.

0:49:050:49:07

Now, can get just the ant on its own?

0:49:070:49:10

-Let's try. He might get a bit angry, though.

-OK, all right.

0:49:100:49:13

I'll try to get him off.

0:49:130:49:15

-They don't like leaving these fragments.

-If you put the fragment where he wants it,

0:49:190:49:22

does he get pleased? Is he going to go, "Oh, thanks"?

0:49:220:49:25

I don't think so. He's still getting angry.

0:49:250:49:26

Fair enough. So, put him back on the scale.

0:49:260:49:28

It's just the ant now.

0:49:280:49:30

So we had 20.7 beforehand

0:49:300:49:33

and now we have...

0:49:330:49:35

4.9.

0:49:360:49:38

So, he was carrying about four or five times his own weight.

0:49:380:49:41

-Yeah.

-Four or five times?

0:49:410:49:43

So the equivalent of even more weights than that.

0:49:430:49:45

And they can even do more.

0:49:450:49:46

They can go up to about 10 times.

0:49:460:49:50

He has been able to carry it, whereas the weightlifter, he couldn't move any more.

0:49:500:49:55

Don't diss the weightlifter, he's still here!

0:49:550:49:58

Thank you very much. I mean, that's absolutely wonderful.

0:50:000:50:03

Thank you for bringing them to see us.

0:50:030:50:06

APPLAUSE

0:50:060:50:07

The reason why ants are so super strong, or seem so super strong

0:50:100:50:13

is because they're so small that they need almost no muscles in their legs to hold them up,

0:50:130:50:19

because they haven't got much volume,

0:50:190:50:21

they haven't got much weight, so almost all of their muscle

0:50:210:50:23

is available for carrying things, and that's just true of everything.

0:50:230:50:27

The smaller you get, the more muscle you have for carrying.

0:50:270:50:30

So, the smaller you get, the stronger you get per weight.

0:50:300:50:35

But there's another animal that's even better than ants

0:50:350:50:40

at doing something else, and that's jumping.

0:50:400:50:43

We realised that before, didn't we? That we have to jump to also be a great dancer, and so it turns out

0:50:430:50:48

that this is also something you can do much better if you're small.

0:50:480:50:52

Now I want to introduce you to a very special guest.

0:50:520:50:55

APPLAUSE

0:50:550:50:57

-My name's Tim and I've got the only genuine flea circus in the UK.

-Wow!

0:50:580:51:04

APPLAUSE AND CHEERING

0:51:050:51:08

So, are we actually going to see some fleas?

0:51:080:51:11

Yeah, I've brought some performers with me.

0:51:110:51:13

We're going to have a demonstration of flea jumping.

0:51:130:51:16

These are untethered and untrained fleas.

0:51:160:51:19

But they won't get out of this?

0:51:210:51:23

No, hopefully not. Fingers crossed.

0:51:230:51:25

Don't worry, guys. We checked this earlier and there's no way they can get out of here.

0:51:250:51:30

This is like Colditz for fleas.

0:51:300:51:32

So we're going to stick one of the fleas on top of the diving board, which is just here.

0:51:320:51:39

And there it goes.

0:51:420:51:44

Where did it go?

0:51:440:51:46

Oh, there it is! How far did it jump?

0:51:470:51:49

-That's incredible!

-About 30 centimetres.

-Wow!

0:51:490:51:51

Look, we recorded something earlier about flea-jumping.

0:51:510:51:55

I just want to show that on this because it's amazing to see them jumping. Here we go.

0:51:550:52:00

Look at them, he's ready to jump, he's ready to jump and off he goes.

0:52:000:52:05

He comes behind here somewhere.

0:52:050:52:07

It's absolutely amazing, isn't it?

0:52:070:52:10

So, how far can they jump?

0:52:100:52:12

These fleas, about 30 centimetres, so several hundred times their own body length.

0:52:120:52:15

Like me jumping to the top of Big Ben, right?

0:52:150:52:18

-Absolutely. You could clear Big Ben.

-Clear it!

0:52:180:52:21

-So we wouldn't need stairs, lifts, if we were fleas.

-Absolutely.

0:52:210:52:24

-They're so good, they spend their time mucking about in the circus, do they?

0:52:240:52:29

-Yeah.

-How do you feed them?

0:52:290:52:32

Well, like the old flea circus owner said, "I live off them and they live off me."

0:52:320:52:37

AUDIENCE GROANS

0:52:370:52:38

-They suck your blood?

-I roll up my sleeves and take one for the team.

-No! That's amazing, isn't it?

0:52:380:52:44

That is love, that is love!

0:52:440:52:47

So I'm really glad that you look after these fleas.

0:52:470:52:51

So, on circus-performing front, what can we see?

0:52:510:52:54

-Are they up for it?

-The performer I brought today is Fifi. Fifi the flea.

0:52:540:52:59

Fifi is a juggling flea.

0:52:590:53:01

-Oh!

-Oops.

0:53:010:53:02

I'll have to pick her up.

0:53:020:53:04

Oh, there she goes!

0:53:060:53:08

No, that's amazing!

0:53:100:53:12

That's amazing.

0:53:120:53:13

AUDIENCE GASPS

0:53:140:53:16

Fifi the flea! Wow!

0:53:200:53:24

-It was a great pleasure meeting you and meeting your fleas and seeing how far they can jump.

-Thank you.

0:53:270:53:33

-Thank you very much.

-Thank you.

0:53:330:53:35

So, we talked about what you had to do to be able to dance.

0:53:400:53:44

You have to be able to stand, have strong legs and have explosive power.

0:53:440:53:49

And you had to be able to jump.

0:53:490:53:52

As you've seen, it, basically, is easier to do all of those things the smaller you get.

0:53:520:53:57

The smaller you get, the stronger you get, the higher you can jump and climb.

0:53:570:54:02

It's so incredibly great being small, but the other way round is also true and depressing, isn't it?

0:54:020:54:09

It means the bigger you get, the harder all those things get

0:54:090:54:14

and the harder it's going to be to dance.

0:54:140:54:17

What we thought we'd do is that we'd turn me into an elephant

0:54:170:54:21

to show you exactly how hard it is for a big thing like an elephant to dance.

0:54:210:54:26

Yeah, let me give you my jacket. So made some trousers -

0:54:260:54:30

what the seamstress has done is they've sewed sand into these things,

0:54:300:54:35

so they're not just heavy at the bottom, they're heavy all the way down and they kind of...

0:54:350:54:41

HE LAUGHS

0:54:410:54:44

It's so heavy that I can't actually get up! But let me just try.

0:54:440:54:50

OK, I'm...

0:54:530:54:54

-Right!

-APPLAUSE

-Thank you.

0:54:540:54:58

Erm...it's actually funny, just standing up in these is exhausting.

0:54:580:55:04

They're so heavy, there's so much weight I'm having to carry and it's quite hard to move your legs,

0:55:040:55:10

erm...but I'm still going to give it a go at dancing

0:55:100:55:16

because maybe even despite all these problems of being big, elephants, maybe they can dance.

0:55:160:55:21

Let's just try it, shall we?

0:55:210:55:23

DISCO MUSIC PLAYS

0:55:230:55:25

-OK.

-OK.

0:55:250:55:26

OK, hand on my shoulder.

0:55:260:55:29

-We're going to mambo. Forward the left. Back on the right.

-Yes.

0:55:290:55:33

Forward on the left, back on the right!

0:55:330:55:36

Thank you. OK, yes.

0:55:360:55:38

Oh, this one forward!

0:55:400:55:41

I think it's... I'm exhausted!

0:55:450:55:48

-Thanks very much for trying, guys, but I think it's hopeless.

-Never mind, thank you!

0:55:540:55:59

See you in a bit.

0:55:590:56:01

All the way through this lecture, it looks like it's really great being small,

0:56:010:56:07

and so maybe you're getting a bit depressed because you're thinking, "Well, I'm too big."

0:56:070:56:12

So I want to end by telling you some good things about being big

0:56:120:56:16

and I want to do that by bringing on Hamish the hamster and Sweep the dog because...

0:56:160:56:24

Here they are. Hamish, did you enjoy the show?

0:56:240:56:27

Yes. Hello, Hamish, how are you doing?

0:56:270:56:31

Now, the thing is that all mammals

0:56:310:56:34

have the same kind of hearts designed the same way,

0:56:340:56:37

so Hamish has got the same kind of heart as me, so has Sweep the dog and even elephants.

0:56:370:56:43

Those hearts will only beat for a certain number of heartbeats until they give up.

0:56:430:56:48

Do you know how many heartbeats that is?

0:56:480:56:51

One billion. That's what you've got. One billion heartbeats.

0:56:510:56:55

That's what Hamish has got, that's what Sweet has got, right?

0:56:550:57:00

So, now. Heartbeats. Let's listen to some heartbeats

0:57:000:57:05

because they're not all the same, are they?

0:57:050:57:08

It actually varies with size. If I listen to Hamish's heartbeat...

0:57:080:57:11

Are you all right, Hamish?

0:57:110:57:13

Let me just do that. Well, it's so fast. It's de-de-de-de-de!

0:57:130:57:18

Really, really fast.

0:57:180:57:20

And now if I listen to Sweep's heartbeat.

0:57:220:57:25

Yeah, it's fast too. Ba-da-ba-da-ba-doo.

0:57:270:57:30

Not as fast, but...

0:57:300:57:33

And my heartbeat is slower still.

0:57:340:57:36

Ba-dum... Yes, calm. No, not really.

0:57:360:57:39

So, that's the funny thing is that the bigger you are, the slower your heart beats

0:57:390:57:44

and the smaller you are, the faster your heart beat.

0:57:440:57:48

But if we all have the same number of heartbeats, which we do,

0:57:480:57:51

that means that smaller things live less long, because they use their heart beats quicker.

0:57:510:57:55

So hamsters live for two years.

0:57:550:57:58

Dogs live for between 10 and 14 years,

0:57:580:58:01

and we, rather triumphantly, live 70, 80, 90 years, which is a great thing to think about.

0:58:010:58:06

So, in a way it all evens up, doesn't it?

0:58:060:58:09

If you're small, you get to jump, be hugely strong, climb up walls, jump off buildings.

0:58:090:58:15

-If you're large, you get to look at all that and live a long life.

-LAUGHTER

0:58:150:58:21

So, I hope you've enjoyed this.

0:58:210:58:22

I hope you realise that size does matter. It matters for you and thank you and good night.

0:58:220:58:28

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0:58:530:58:54

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