Why Elephants Can't Dance Royal Institution Christmas Lectures

CHEERING AND APPLAUSE

Well...

Hello, everybody. Hello.

My name is Mark Miodownik,

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

I'm going to talk you about stuff.

You're all made of stuff.

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

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

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

The Royal Institution - such a civilised place!

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

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

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

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

The spoon is made of stuff.

Stir my cup...

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

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

Now...while we're on incredible,

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

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

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

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

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

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

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

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

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

Right?

PHONE RINGS

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

This stuff doesn't hurt mobile phones at all.

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

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

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

So, stuff really can just take you completely unawares.

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

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

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

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

Now, a Geiger counter detects radioactivity.

BLEEP

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

Phew!

CLICKING

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

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

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

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

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

which is going to involve understanding about size.

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

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

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

But it turns out not to be true.

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

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

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

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

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

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

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

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

Quantum mechanics, very strange stuff goes on.

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

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

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

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

it's the surface forces of this crystal plane.

It's actually very sticky. Oh!

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

and how size affects animal behaviour.

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

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

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

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

Wonderful, huge creatures, amazing things.

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

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

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

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

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

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

Cats? Dogs? What have you got?

-SHOUTING

-Dog? Crocodile?!

OK, all right. Fantastic. Now...

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

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

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

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

This is the Burj Khalifa, and it is huge.

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

It is very scary. Half a mile down.

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

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

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

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

He was up for jumping.

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

Jumping off a building...

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

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

Does size matter when it comes to falling off buildings?

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

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

Ah, here's Hamish.

Hello, Hamish.

And Sweep. What's your name?

-Charlotta.

-Charlotta, and you're...?

-Alan.

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

How sweet, they're both happy.

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

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

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

And what about Sweep the dog?

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

-No one does.

-I do!

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

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

How can we decide if this is true?

Well, let's do an experiment, right?

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

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

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

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

Come on!

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

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

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

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

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

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

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

All right, so, this is pretty exciting.

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

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

Now, what are these crash-test pets?

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

It replicates the flesh of a...

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

He's ready, isn't he?

And this is crash-test hamster.

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

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

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

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

And they're both made of the same material.

So this is a fair comparison.

Sometimes they don't want to jump,

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

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

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

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

5, 4, 3,

2, 1...

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

Yes!

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

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

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

Good one. He's all right.

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

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

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

Let's get crash-test dog in here.

How's he feeling? All right.

Crash-test dog, up he goes.

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

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

All right. 5, 4, 3,

2, 1...

Oh!

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

Yeah... I think...

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

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

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

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

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

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

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

One is bigger than the other.

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

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

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

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

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

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

Yes, would you like to volunteer?

Yes.

APPLAUSE

Hello. What's your name?

-Annie.

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

Here we go. This looks like some weird game.

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

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

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

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

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

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

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

Let me just prove that to you.

So, this is seven and a half in width,

diameter. And this is 15.

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

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

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

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

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

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

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

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

4/3 Pi r cubed.

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

-Go on then. How many do you think?

-Eight.

-Eight? Are you sure?

-Yes.

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

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

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

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

You think eight.

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

That's two.

All right, that's three.

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

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

A little bit. That's six.

This is seven.

Here we go. Oh...

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

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

Yes!

You! You!

Thank you very much for that.

Do have a seat again.

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

You increase something twice, the width or diameter twice,

and your volume increases by eight times.

Oh, crash-test dog is back!

He's bandaged up. He survived.

The show must go on, mustn't it.

How are you feeling? Oh, not too talkative.

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

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

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

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

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

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

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

100 times.

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

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

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

Do you guys believe me on that one?

Do you think that's at all believable?

100 times heavier?

Well, I've got some scales here.

Let's just have a look at that.

Let's measure it.

Crash-test hamster is about 100 grams.

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

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

just over 10 kilos.

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

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

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

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

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

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

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

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

it's how much you can spread it out.

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

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

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

than crash-test hamster, don't we?

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

with a 3D scanner, these two animals,

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

Surface area of crash-test hamster is 100.

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

That's a bit concern-making now.

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

Too late, I know what you're saying.

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

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

This tells you something really fundamental about making things bigger.

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

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

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

That really means that when you hit the ground,

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

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

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

We knew it survived.

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

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

It got 100 times more force,

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

the pressure on all its extremities

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

So, there it is.

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

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

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

There's something else that helps you too.

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

Things don't always fall at the same speed.

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

I've got a snowflake

and I've got a snowball.

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

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

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

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

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

because they've got the same weight.

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

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

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

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

We know this. Snow falls very gently.

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

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

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

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

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

So, we know the rules now.

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

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

then I could manipulate the rules maybe.

Let's say I jump off the building.

I'm falling through the air,

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

Doesn't that always happen after you jump?!

So, I think, Hamish!

Chuck me the umbrella! Thanks.

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

So, I'm going to slow down,

and I fall much slower.

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

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

So, parachutes work because they change...

You cheat, you change your surface to area ratio.

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

So, that's really cool.

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

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

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

But that's really what's happening.

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

this ratio, and survive falls.

It's really important in your whole life.

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

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

Why are you obsessed with my height?

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

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

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

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

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

And they were totally fine, swimming around for hours.

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

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

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

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

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

So you're going to shiver.

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

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

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

You really do need to put coats on them.

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

But could we find examples

of nature manipulating it in other ways?

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

I was looking at the ceiling

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

I was thinking, how can it do that?

That's really mad.

And so,

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

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

-Yes.

-Gordon Gecko.

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

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

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

-He is indeed.

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

-Would he have a go?

-Yeah, sure.

-Will he be camera shy?

I'll give him a go.

Might be a bit noisy.

There he goes. He looks a bit annoyed.

-Is he a bit annoyed?

-He's all right.

They do have a bit of a temper on them.

Is it because he hasn't eaten or something?

-No, he's all right.

-He's been eating, OK.

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

-Ready?

There he is! Look at that!

APPLAUSE

Now, how on earth does he do that?

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

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

-Can we just leave him there?

-Yes.

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

I was thinking in my hotel room,

I was having a word with Hamish the hamster,

and we came up with four possible explanations.

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

So you guys can run with me on this one.

We thought that it may be

that geckos have some sort of glue on their paws.

A bit like a spider squirting out glue,

and that's how they can walk up walls.

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

Option number two is that they actually have nails.

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

And that's how they get up these walls.

-Is he all right?

-Yeah, he's fine.

I'm talking about you, gecko.

Yes, yes!

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

that they have little suckers on them,

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

Suckers, impressed? Well, all right.

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

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

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

Who votes for that? Oh, no-one.

Who votes for the nails.

Come on! It was quite a good idea.

No?

Who votes for suckers?

Suckers!

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

And who votes for the hairs?

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

Not often you get to say that, is it?

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

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

Let's have a look under the microscope.

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

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

this is really high magnification,

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

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

Actually hairs on the end of hairs.

It's hairs on hairs

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

This gecko has hairy hands.

However ludicrous that sounded, it is the truth.

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

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

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

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

Thank you very much.

Geckos climb up walls using hairy hands.

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

What's going on there?

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

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

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

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

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

the dog denier.

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

OK. Girl power versus boy power.

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

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

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

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

Two health and safety manuals.

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

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

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

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

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

Right, ready? Are you guys ready?

Steady... Go!

Yes! And the girls are really holding on!

What's happening to this?

What is happening to this? Come on!

Yes!

SHOUTING AND CHEERING

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

Well done, guys.

What also won here was these books.

Yes, I know. Are you all right?

-They always win.

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

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

HE BLOWS

Have a look at that. Look at that.

OK?

That's mad, isn't it?

No glue, right? Just paper, no glue?

-No.

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

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

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

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

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

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

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

Get the telephone directories, all right?

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

Why is it such a strong force?

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

is tiny molecular forces between the two sheets.

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

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

and by having every single piece of paper over each other

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

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

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

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

This is what happens if you magnify a wall.

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

or a surface and think that's quite smooth.

But under the microscope, surfaces are very rough.

They look like mountains, right?

So, if you're touching something...

So, this is a massive me.

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

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

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

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

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

just touch the tips of the mountain

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

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

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

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

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

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

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

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

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

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

They are maximising an area of contact there,

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

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

these surface forces, which are tiny,

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

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

That's pretty impressive!

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

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

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

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

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

which is trying to do exactly that.

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

If we go here and we look in...

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

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

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

stick things onto it.

Oh! It's a prototype, OK?

No, it does work, actually.

There it is. Yes!

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

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

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

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

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

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

You could infinitely reuse this stuff.

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

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

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

and that liquid flows into the mountains,

the rough mountains of this surface,

and then it maximises the area of contact,

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

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

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

I know you guys!

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

you already know there's a problem.

Which is that although the adhesive force goes up,

if your volume isn't matching that force,

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

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

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

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

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

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

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

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

OK, so, fantastic!

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

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

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

This are what my lungs looked like.

I'm going to put it exactly...

There we go. No, there we go!

Now, I'm breathing in,

and these lungs are exactly the right size for me,

so air is coming into these lungs.

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

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

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

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

At that moment you breathe in,

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

So it's taking oxygen from a large volume

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

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

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

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

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

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

That's exactly what you want.

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

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

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

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

because you can't really see it here

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

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

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

OK, we've got it here.

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

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

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

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

that all this area could be inside your body.

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

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

Right, you guys let go. Let it go.

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

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

Essentially, that is what happens when you smoke -

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

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

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

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

So, this whole thing is incredible.

The surface to volume ratio, right?

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

It can help geckos climb up walls.

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

but it does something even more important than that.

It can determine whether you can dance or not.

Whoa!

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

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

-What are you names?

Chris Marquez, Jaclyn Spencer.

Fantastic. You dance so brilliantly.

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

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

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

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

-All right.

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

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

-Yeah.

-You've got to be able to stand.

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

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

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

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

-Yes, OK.

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

-It all goes through here.

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

So, standing up, strength, jumping.

If I can do those things, I can dance.

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

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

-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.

-Ten.

-Ten.

-Ten.

-Bring it on!

OK, so...

Now, look, standing!

That doesn't seem too hard, does it?

But is it? Is it as simple as that?

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

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

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

That's a step forward, literally!

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

has got to go through its legs, OK?

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

All of the force is coming through them.

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

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

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

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

It's got four legs, fantastic.

What happens when I size it up -

I scale it up and increase its width by two.

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

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

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

That would be fine if the area of its legs

had increased by eight times -

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

-What do you think?

-No.

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

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

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

running through it and that means that...

it can't actually stand up.

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

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

you will collapse under your own weight.

Now, you don't think that this happens,

but actually this is what happens with elephants.

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

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

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

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

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

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

They make their bones bigger, they make their legs bigger

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

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

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

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

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

And it's not a style choice, OK?

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

Surely that should make them stronger?

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

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

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

CHEERING AND APPLAUSE

-So, what's your name?

-My name is Terry Hollands.

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

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

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

CHEERING AND APPLAUSE

So, you say that...

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

-Yeah, sure.

I lifted these weights earlier...

LAUGHTER

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

Yeah.

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

-Yeah, sure.

DRUM ROLL

Whoa!

CHEERING AND APPLAUSE

Did you see the bar bending?

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

-Yeah.

That's absolutely amazing.

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

Do you mind asking how heavy you are?

Sure, I'm 180 kilos.

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

-That's 380 kilos.

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

-Yeah.

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

-Yeah, pretty much a small car.

-Could you lift a small car?

-Yeah, yeah.

Wow!

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

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

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

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

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

-The heavier guys would be just over two.

-Absolutely fascinating.

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

-Great.

Thank you very much.

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

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

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

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

-What's your name, sorry?

-My name is Karen Wall.

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

-Welcome.

And I do actually study how ants manage to

carry large loads.

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

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

-So these are basically the leaf cutting ants.

-Look at this one!

-Look at that!

-Yeah, it's amazing.

He's showing off, isn't he?

-He is showing off, yeah.

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

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

my sofa up some stairs...

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

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

All right.

Brilliant, OK. Nice one.

He doesn't look too annoyed.

He's still got his sofa.

So now we have 20.5 milligrams.

OK, 20.5 milligrams together.

Now, can get just the ant on its own?

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

-OK, all right.

I'll try to get him off.

-They don't like leaving these fragments.

-If you put the fragment where he wants it,

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

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

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

It's just the ant now.

So we had 20.7 beforehand

and now we have...

4.9.

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

-Yeah.

-Four or five times?

So the equivalent of even more weights than that.

And they can even do more.

They can go up to about 10 times.

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

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

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

Thank you for bringing them to see us.

APPLAUSE

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

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

because they haven't got much volume,

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

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

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

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

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

at doing something else, and that's jumping.

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

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

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

APPLAUSE

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

-Wow!

APPLAUSE AND CHEERING

So, are we actually going to see some fleas?

Yeah, I've brought some performers with me.

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

These are untethered and untrained fleas.

But they won't get out of this?

No, hopefully not. Fingers crossed.

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

This is like Colditz for fleas.

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

And there it goes.

Where did it go?

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

-That's incredible!

-About 30 centimetres.

-Wow!

Look, we recorded something earlier about flea-jumping.

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

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

He comes behind here somewhere.

It's absolutely amazing, isn't it?

So, how far can they jump?

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

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

-Absolutely. You could clear Big Ben.

-Clear it!

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

-Absolutely.

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

-Yeah.

-How do you feed them?

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

AUDIENCE GROANS

-They suck your blood?

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

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

That is love, that is love!

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

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

-Are they up for it?

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

Fifi is a juggling flea.

-Oh!

-Oops.

I'll have to pick her up.

Oh, there she goes!

No, that's amazing!

That's amazing.

AUDIENCE GASPS

Fifi the flea! Wow!

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

-Thank you.

-Thank you very much.

-Thank you.

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

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

And you had to be able to jump.

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

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

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

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

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

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

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

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

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

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

HE LAUGHS

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

OK, I'm...

-Right!

-APPLAUSE

-Thank you.

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

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

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

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

Let's just try it, shall we?

DISCO MUSIC PLAYS

-OK.

-OK.

OK, hand on my shoulder.

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

-Yes.

Forward on the left, back on the right!

Thank you. OK, yes.

Oh, this one forward!

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

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

-Never mind, thank you!

See you in a bit.

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

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

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

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

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

Yes. Hello, Hamish, how are you doing?

Now, the thing is that all mammals

have the same kind of hearts designed the same way,

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

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

Do you know how many heartbeats that is?

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

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

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

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

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

Are you all right, Hamish?

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

Really, really fast.

And now if I listen to Sweep's heartbeat.

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

Not as fast, but...

And my heartbeat is slower still.

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

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

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

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

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

So hamsters live for two years.

Dogs live for between 10 and 14 years,

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

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

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

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

-LAUGHTER

So, I hope you've enjoyed this.

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

Subtitles by Red Bee Media Ltd