The Secret Life of Waves

My name is David Malone.

This is Tynemouth, where I was born.

And the place where my parents came back to when they retired.

What I really remember is standing down there.

Where the guns...?

-No, where the gate is, and watching the waves go by.

-Oh, right.

-I used to take you there.

-Did you?

I used to go down to this particular sea wall when I was a little lad.

The angle of the wall to the curl of the wave meant that

it always trap air inside the wave, compressing the air,

which would then escape and make this wonderful roaring sound

as the wave came down the length of the wall towards you.

I make science documentaries

and I believe a deeper understanding of waves

can explain our endless fascination with them.

When we started out, this film was supposed to be

about the science of ocean waves.

But it can't be about just that, because waves also give us a window

into how the world actually works,

into the nature of reality.

Because waves have a life cycle,

so they're quite unlike the things that we think of as objects,

like pebbles or cliffs.

They have a birth and a death.

They're a process, and that makes them much more like us.

There's a view that science is merely about totting up numbers

to make them come out right,

while how we make sense of the world should be left to the poets.

I don't think that's right.

Waves in particular is one of those subjects

where the science itself is full of meaning.

Why are waves so fascinating to watch?

Why is it that human beings will sit

and be hypnotised by waves for hours?

We don't normally sit and watch chairs and tables.

All my life I've gazed at the sea breaking on the shore

and wondered what makes each wave different

and why they crash so relentlessly.

I was surprised to discover that the scientific study of waves

began only relatively recently,

and it wasn't idle wave-watching.

It was truly a matter of life and death.

Autumn 1942.

During the Second World War, the first major amphibious landings

were planned to attack German forces in North Africa.

The Allies knew that the landing craft carrying troops ashore

could capsize in waves over six feet high.

It was essential, therefore, to predict the height of the waves.

Scientists found they could calculate wave heights accurately

by measuring the duration and strength of the wind.

The ability to predict waves

led to the success of the landings in North Africa...

..and later on, D-day in France.

To understand these wartime discoveries about waves,

'it's easier to start not at sea, but at Flatford Mill in Suffolk,

'made famous in the painting by Constable.'

Well, we've got a virgin canvas here, ready for waves to start.

'Gavin Pretor-Pinney is an author who studies waves.'

The whole idea of the birth of a wave is a rather intriguing notion.

-It's got to start somewhere.

-I hadn't thought about it before.

I suppose what I'm interested in is how does a wave get born?

It does seem a bit like getting something from nothing.

Cos there you've just got water,

and somehow you've got to get a wave out of it.

Well, now the air is quite still.

But in the case of winds out at sea,

there is the wind.

That is the crucial factor.

That's where the energy comes from.

-How?

-Well, I'll show you.

I'll get down and I'll be the wind.

OK.

On this little flat bit here...

-Right.

-It really very easily happens.

It doesn't require a lot, does it?

And these tiny little ripples that I produce by blowing over the surface,

they're known as capillary waves, these tiny embryonic waves.

The critical factor is the surface tension of the water.

When the water is distorted into a slight crest,

the elastic nature of the surface wants to flatten it down.

In terms of it being a wave that propagates over the surface,

this returning, this restoring force, is critical.

Is that what helps to push it away?

It helps to make the wave move because,

where it's lifted up, the restoring force brings it down,

-and then it overshoots...

-Pushing the wave that way.

It continues down below and as the parts of the water go like this,

the actual shape of the wave progresses across the surface.

In the mill pond, as the wind creates a wave,

the surface tension tries to flatten the water.

The result is a regular undulation in the surface.

Naturally, the forces that create waves out at sea

are very much greater.

The sun provides the earth with energy in the form of heat.

This warms the atmosphere and creates the wind.

It is the energy of the wind that in turn creates the waves.

Energy is the invisible force that drives the universe.

Energy can never be destroyed.

It can only change from one form to another.

Even after the wind dies away, the energy lives on in the waves.

These ocean waves are far larger than capillary waves,

and forces other than surface tension take over,

pushing the water down.

-Better get out the way.

-Yeah.

'We can see this if we increase the wind at the mill pond.'

Right, let's turn it round here.

That's good. Shall we start her up?

We shall.

LOUD WHIRRING

WHIRRING STOPS

So that, you could see...

God, I can hardly hear now!

You can see that they soon develop into larger than these

2cm-high capillary waves.

And they're continuing much more.

Can you see the bunch of them coming back?

Capillary waves themselves, when they're tiny, they don't go very far,

but once they get larger than a couple of centimetres,

they're known as gravity waves.

Why are they called gravity waves? Why the change of name?

There are two forces that try to return the water to the level.

One is the surface tension that we were talking about

with the capillary waves. The other is the force of gravity.

When the waves are greater than a couple of centimetres,

that becomes the dominant force.

With these larger waves, gravity works just like surface tension.

It pushes the wave down, overshoots, and the wave is propelled forward.

-That's beautiful! Look at that!

-That is beautiful.

A very graceful movement, isn't it?

It is lovely.

The thing I was quite sceptical about...

I mean, I knew it intellectually, but there's something about someone

getting down on their knees and blowing onto the surface

of the water making a few ripples,

and then saying, "And that's how you start a Pacific wave."

It doesn't quite grab you that some 40ft monster that

can throw a boat about starts off life as little teeny ripples.

And yet, as soon as you brought the wind machine out,

you could see that that's exactly what it was.

The thing for me about being on the sea is it reminds me

how different an environment the sea is to the land.

Most of us live in cities

where we're cut off from the nature of power and energy.

For us, you just flick a switch and there's power.

It flows through wires,

lights come on, records play and your dinner heats up.

But we're unaware of what power is.

When energy was generated by rushing water,

or even by steam, we had a visceral knowledge of what power was about.

Water rushed by and cogs turned and hammers went up and down.

Today it's all hidden from us

and we live in such a static, calm, quiet environment.

It's not until you come back out on the sea, you're reminded

of the real nature of the dynamic, the powerful side of reality.

For me, what's so exciting about waves

is that they reveal what is normally hidden from view.

You can actually see energy in action.

They provide insight into the forces that rule the universe.

One of the strangest things about waves

is they're not really made of water.

I know it doesn't sound right, but they're really not.

Think about sound. Think about the words I'm saying.

You wouldn't describe them as MADE of air.

You'd say they're vibrations IN the air.

And it's the same for waves.

I've come to Cambridge University to find out more

'about this counterintuitive idea that waves are not made of water.

'Professor Michael McIntyre, a leading physicist and mathematician,

'wants to prove it to me.

'He's fascinated by the relationship between atmosphere and ocean waves.'

What a fab lab, don't you think?

Oh, it's a beautiful lab, and Stuart does a great job

running a facility like this. It's a great tradition in our

department to do experiments as well as mathematical theories.

And I think you need both to understand how things work.

Stuart, can you make a wave break around here?

Certainly.

The gentle waves out here

-aren't moving the water very much except back and forth.

-The ducks!

That gives you a visualisation of how much the water is moving.

It is moving a bit, but the main motion is an oscillation.

The ducks are going round in circles.

Yes, they're certainly not travelling with the wave.

Not nearly as much.

So most of the water, then, is just going up and down?

Well, it's actually going in little circles or ellipses.

Watch that duck carefully. You see?

Oh, yes. You can feel that when you stand in the beach.

When the wave passes, it pushes you one way

and then drags you back the other. Is that the same thing?

Yes. That's the oscillatory part of it.

'Professor McIntyre's ducks show it's not the water that's moving'

but the energy.

The water and ducks are essentially stationary.

They go around in a big circle, almost back to where they started

from, while the waves of energy move onwards.

There's a surprising parallel to waves

in an executive toy.

The balls in the middle hardly move,

yet the energy passes through them and out the other side.

The balls are the medium that transmits the energy

just as the water does in waves.

Hello, Dr Porter!

'Physicist Richard Porter has studied waves for 20 years.'

Picked a good morning for it, at least!

-This is beautiful!

-'He researches them as a source of power.

'I met him at his open-air wave tank, the sea off North Devon.'

Waves are a form of transport of energy.

That's the way I would describe it.

And the water is what? Just the medium?

The water just acts as the medium.

In this case, it's the water that acts as the medium for

transporting that energy in the form of this wave.

-Like sound going through the air?

-Exactly.

I'm talking to you, and the acoustic wave that you're hearing

is a wave which happens to propagate through air using particles of air.

-And out there...

-And out there, you just happen to have waves -

the energy which is travelling along the surface of the water.

So there is no net transport of water.

Yes. When we're standing on the beach,

you get the impression that those waves are bringing the water in,

but that is not right.

-No, that's not right.

-Because they appear to be bringing it in,

even when the tide's going out.

That's right, and if they were bringing in water,

then we'd all be doomed. Everything would flood.

So that's not what happens.

What you see is the water coming in and going back out again,

on a cycle, with the waves coming against the shore.

When I watch the sea, I love to listen to the sound of the waves.

I learned from Dr Porter that very little of the energy is lost

as a wave travels across the ocean,

but when it breaks on the shore, the energy must go somewhere.

Some energy is absorbed by the sand,

some bounces back into the sea, and some turns into sound.

You've got some water, you've got some air,

you drop the liquid in

and you listen to the sound here.

-Can we do that, then?

-Let's have a go.

Let's see what happens.

'Tim Leighton is the bubble man or, more formally,

'Professor of Acoustics at Southampton University.'

OK, here comes the drop.

'We've all heard the drop of a leaky tap.

'But the question is, what exactly is making the noise?'

It hits, forms this crater - lovely crater -

closes, pinches off the bubble...

-That tiny thing there?

-That little thing.

All the ripples on the surface, which are very impressive visually,

don't radiate the sound.

It's that tiny little bubble.

When magnified and slowed down, the bubble constantly moves in and out.

It's the vibrations of the bubble, be it from a drop of water or inside

an ocean wave, that produce the noise.

Hidden away amongst them are pulsations, microscopic,

and the pulsation is pushing the water in and out, in and out,

as it expands and contracts.

Until this moment, I'd never realised there WAS a bubble,

let alone that its pulsing made the noise.

When you were talking about bubbles,

there was the temptation to think it's when they pop.

-I was thinking of balloons.

-No.

-It's not at all?

-I don't think they're kosher bubbles!

-You've got MY kind of bubbles...

-When you're president you're going to ban them!

..are pockets of gas surrounded by water.

Now, the other kind of bubble - a soap bubble for example - has gas

-and then a thin wall of liquid and then gas outside.

-Right.

But it doesn't have that huge mass of liquid around it,

providing the inertia, so it won't act

like a really powerful sound source like this.

The sound a bubble makes depends on its size.

We can hear this if we release two different-sized bubbles.

What you can see here is the bubble on the left is giving out the big bubbles.

That is the regular, "blonk, blonk, blonk".

The smaller bubble, coming out of the needle on the right,

gives you a high "plink".

-If it's a different size, it gives you a different note.

-Pretty much, yes.

It just so happens that these millimetre-size bubbles

give out plinks at the frequencies we can hear,

which is why babbling brooks makes a poetical babble that you can hear.

If the numbers came out differently, the babbling brooks would be silent and we'd have lost all that poetry.

-But as it is...

-So wait a minute,

if the bubbles were just way too small, we wouldn't hear them at all.

Yeah, that's right. That's right. The numbers turn out just right

so that the babbling brook and the waterfall and such like are musical.

-Fantastic.

-Yeah, it's nice, yeah.

-That is quite good, isn't it?

In a wave - obviously I've never even thought of trying to count the bubbles in a wave -

but we were on the beach a couple of weeks ago,

and it was just a wall of Atlantic surf, and it was just white.

It was about, I don't know, eight foot of whiteness,

-that's all bubbles, isn't it?

-Where you see white...

Just a metre of that must have been an uncountable number of your bubbles?

Yeah, and each one is giving a noise,

which is why we think of oceans and waterfalls as being noisy, and it is a very powerful noise.

-But we don't think of them being noisy, they are.

-They are.

The noise of an ocean wave is made by all the bubbles, all heard at once.

Slow the sound of the wave down far enough...

..and we hear the individual notes, each from a bubble vibrating.

Multiply the bubbles up a trillion-fold and they become the song of the ocean.

Each bubble is like a little bell giving out a very pure note

and what you see there is, you've got a wobbly sea surface, and then a couple of thousand bells,

-and it's obvious where the sound's coming from.

-It is now, it is now.

It's not just scientists who want to know what happens to the energy after it's crossed the ocean.

-Morning, gentlemen.

-Hello, there.

-Good to see you again.

-Morning, mate.

'Surfers also need to predict the arrival of waves.'

-Did you know it was going to be flat today?

-Yeah.

How do you predict the waves?

Is it something you have to do with surfing? I presume it is.

The earlier you know the waves are going to be good,

the easier it is to make a decision about where to go surfing.

So you can use, you can check on mobile phones,

I can check out the synoptic weather charts which gives you an idea where the low pressure is going to be.

And ideally when you get here, you want the wind to be blowing off the land,

which will make the waves smoother and give us a cleaner wave to surf.

What we're looking for is one perfect band of energy, really, moving in sets, unaffected by anything else.

What do you mean by a perfect band of energy?

Say there's a storm, north of Scotland and it's nice and tight and it creates one swell,

then that swell travels and over a period of time it becomes formed into nice long lines of waves.

Pulses of energy.

And it's that energy you're looking for. Is that what you're surfing, the energy?

Yeah, we're just looking to ride the energy.

On the perfect days, the water doesn't really move...

-That's fantastic.

-..So the energy is just moving through the water.

And the purest experience is the nearest you get to the pure form of energy.

So the oscillations as they come to the shore, as they continue in,

that roundness, that hollowness.

Surfers know all about the energy of the wave and how its energy has to go somewhere.

I love the way surfers understand this as well as any scientist.

Richard Porter has explored why it is that waves contain so much energy.

If you really want to think about how powerful a wave is,

you just think about sitting on a boat, just a little boat, somewhere out to sea,

and imagine you're sitting there and the boat is moving up and down.

But imagine how much power you'd need to give to that boat

just to lift it up and down. And that energy comes from the wave.

If you had to do that on land, it would take a large group of men to lift that up.

-Well, yeah, machinery to do that.

-Whereas, on the boat, on the sea...

-It just happens, right?

So it is a huge, huge amount of energy in a single wave.

Surface waves are a fantastic way of storing energy

because they take energy, which occupies a three-dimensional space.

Like wind or something.

Wind, it occupies the atmosphere, it's three-dimensional

and it transmits its energy to these surface waves,

these waves that you see on the ocean, which exist upon the surface of the water.

So they've kind of concentrated it.

Yes. So you've taken this three-dimensional space,

full of energy and you've transmitted it into a two-dimensional surface,

and that's a way of focussing the energy.

Which is what you see out there?

Exactly.

Yes. That makes sense to me.

I've always thought of waves as being on the surface of water.

Professor McIntyre showed me that there are other types of wave hidden below.

The energy that creates many of these internal waves doesn't come from wind.

They owe their existence to temperature and salinity differences IN the ocean.

In this tank, the heavy blue liquid lies underneath a lighter clear one.

This sort of thing is more what you see near coasts,

where a river runs out over the ocean and makes an interface.

If you look along...

And I can just see them curve, beginning to go over...

And they're going the other way, so you can have different waves going in different directions.

-And they're not affecting each other.

-Not very much. And this comes out of the mathematics.

But is this what you get in the ocean?

You get waves doing something down below and in addition to the surface waves?

Yes, you get them at all levels. You get them on any interface.

There's an air-water interface, there's a water-water interface.

So you get that kind of wave on the surface, that's what we're used to,

and then 20 feet or 50 feet or whatever it is,

you've got this going on, which we don't normally see?

Yes.

Professor McIntyre's work shows that surface waves are just the start.

Beneath them are larger internal waves which run in different directions to those on the surface.

There are some very important waves in the ocean which break sideways, known as Rossby waves.

The thing can move sideways and there's a fundamental sideways wave motion, called Rossby waves.

I walked in here this morning just having one kind of wave!

-I've got about five now.

-But if you want to understand the ocean,

-you have to have at least five. I can mention more if you like.

-Please don't.

Let's take Rossby waves, cos they're fundamentally important.

To understand how jets form you have to understand Rossby waves

and how they break and they do it all sideways.

-Is that what it is?

-If you think of the gulf stream,

it's essentially a jet with Rossby waves on it and they're breaking all the time.

That means they're throwing off eddies, sideways,

and that's a kind of wave breaking, from a Rossby wave perspective.

And that wave breaking is fundamentally how the jets sharpen and maintain themselves.

How they stay narrow.

Rossby waves allow the Gulf Stream to flow like a river

within the Atlantic ocean, for thousands of miles.

Without these sideways eddies, the main current would break up,

the warming effect of the Gulf Stream would disappear and Europe would freeze over.

We have seen how energy travels through water in the ocean

but other waves of energy are found throughout the universe.

The world is actually filled with waves, it's just that we can't see them, generally.

Right here, there are quantum waves, light waves, sound waves.

There are sound waves distorting the air between me and you right now, but we can't see them.

They happen on a time scale that we can't appreciate or physically at a scale we can't appreciate.

The one place where you really see this other reality is in the water.

That's where you can see the waves doing what they do, making the world work.

And once you realise that, you realise that the familiar world,

the static world of rocks and cliffs, is just one side of reality,

there is this other reality where everything is actually in motion, in process.

It is this that makes water waves so fascinating for me.

They're not made of water, so a wave isn't really a tangible object.

Waves are process.

Michael McIntyre recognises that process is the important side of reality,

yet it's often hidden from us.

If we want to understand anything in depth,

we usually find we need to think of it both as objects

and as dynamic processes and see how it all fits together.

I always tell my students, "What is understanding?" Understanding means being able to see something

from more than one viewpoint, make it all consistent, do it in equations, in words, in pictures.

make it all hang together consistently.

Very often we say, "OK, that's an object but if you zoom in you'll see a process."

Do you like that Heraclites quote,

that everything flows and nothing persists, or nothing endures?

Well, I'd agree with him, certainly.

Our whole understanding of the cosmos says that that's the case.

And waves are the archetype for that.

That's why we thought we would make this film on waves, as the science of change.

Because, you can understand that quote and the idea of process,

intellectually, but it's very difficult to see it most places, isn't it?

I mean you can't stare at a table and see it as a process. It's an object.

-But waves, it's right there, isn't it?

-Yeah, ordinary waves on the surface of the sea,

they're highly visible, so they give us all sorts of new ideas.

Understanding waves reveals the processes that govern the universe and therefore govern our lives too.

Almost by definition, waves are about the transformation of energy and so are people.

We harness energy to keep us alive, from cradle to grave.

Without this constant throughput of energy, we'd just be a pile of atoms.

Our lives are in continuous change.

As you get older, especially once you've had children,

you start to think that life maybe really is a process.

It stops being just you as a static thing in your life

and suddenly there's a process of your parents getting older and your children coming along,

and life seems somehow to be moving,

like a wave, it's shifting along and you're going with it.

And for me, it was quite a fundamental change.

To have children, to grow older, it's all part of our life-cycle, a dynamic process of change.

Seeing our lives as process is part of a philosophical debate that's long intrigued me.

The debate is over whether it is more fundamental, more true,

to view the world as objects or as processes.

I think most of the time, we see the world as a collection of objects.

This is because so many processes are invisible.

Take the creation and erosion of a coastline.

It happens over thousands of years, a period of time inaccessible to humans.

To us, on the beach, the coastline appears static and inviolable.

Except for waves, virtually everything around us is like this,

and that's perhaps why humans are hard-wired to perceive the world as full of objects.

But Richard Porter, who constantly studies waves, has a different perspective.

Making mountains is a slow process,

but, clearly, it's a very powerful process.

And this is a fast process on that timescale,

-but it's a timescale that we can actually observe.

-It's a human one.

And waves are a way of doing that, to remind people, actually, the world isn't a static place,

that it is full of this energy, which is doing things.

Yes. I think that waves in some ways

are almost uniquely placed in that they are essentially things

that are created and destroyed in equal measure.

They're always being created. They're always being destroyed.

And you think of all of the other types of natural forces that you see at work,

and you don't quite see that level of dynamism that you have.

You tend to see one end of the process or the other.

With wind, you see wind generated and then it disappears off somewhere

and you don't really get to know where it goes.

But you've got this continual sort of, these waves coming in, continuously.

It is this permanent exchange of energy.

Professor Markus Kirkilionis uses maths to model the natural world.

He pushes the concept of waves further than anyone else.

-Hello, Professor Kirkilionis.

-Nice to meet you.

-Nice to meet you too.

We've talked a lot to physicists and I can see why they're interested in waves,

why are they important for maths? Do you see waves when you look around,

when you look in the world, do you see other waves?

Oh, I see waves everywhere, to be honest, yes!

Just look at this marvellous city.

It has spread for centuries.

If you would now give me a map of London,

let's say 500 years ago and we would gradually, every 50 years, look at it,

you would actually see a wave-like structure evolving.

If you compare such a city,

with all its processes that are going on all the time,

you have a lot of similarity to all this,

to the waves in the ocean at a very windy day, where a lot of things are going on.

What is interesting for us in a wave is usually it's dynamic behaviour, that it does something,

it transmits something, like information or energy and...

And also its very, being is slightly more tenuous. That's the thing that's interesting to me.

You look out at buildings and there's this notion that we don't need to worry about them,

they're just going to be there forever.

The energy within a process is always changing.

The energy within an object is locked in place.

But perhaps this constancy of an object is just an illusion.

Whether we can call something a static thing or a dynamic thing,

that really depends on the timescale you are observing it

and that's a general principle that is, of course, also valid in mathematics.

But is it still worth having the distinction between objects and processes?

I mean, take St Paul's. Now is that an object for you?

Well, I think for us humans, it is naturally an object first,

because our lifetime, compared to St Paul's, is much shorter,

so we will not see any change in this object.

Also, the physical forces inside the building, you know, all the atoms,

together, they form something solid which will not change in time,

at least not over the time we both can observe it.

And that is a principle that applies to a lot of mathematical objects as well.

It does work at a mathematical level?

Yes, so typically in the mathematical equations,

you can distinguish between solutions that are constant in time -

we call them equilibrium solutions or steady states -

and other solutions to the same equation that are non-constant - we call them transients, very often.

-And the wave would be typically a transient...

-Ah yeah, yeah.

And you can study these objects, for example, in terms of their stability.

So there is this distinction between stability and instability in the world.

Which means the division between object and process,

between a cathedral and a wave,

is actually based on a bedrock of mathematics.

It was mathematics that was central to the work on wave heights

during World War II.

A young oceanographer by the name of Walter Munk

found a way to predict the waves for the invasion of North Africa.

Munk realised that the height of the waves

was directly correlated to the wind energy injected into the waves.

So what were the things that he was looking for?

So he worked out there were three crucial factors

in determining the size of the waves.

One is the strength of the wind

blowing over the surface of the water.

So the strength of the storm winds.

-The second is the duration that that wind is blowing for.

-Right.

And the third is what's known as the fetch,

which is the area of sea that the wind is blowing over.

So the longer the fetch is,

the greater the distance that this wind is blowing across.

And these three factors all determine

how much energy the wind gives to the surface of the water.

Imagine the kind of responsibility -

he was 26, 27, and he had the responsibility of determining...

Of picking dates for these amphibious landings in North Africa.

You know, that's a lot of weight on your shoulders.

'After the war, Walter Munk carried on with his research.

'He was the first to suspect

'that the energy contained in a wave is remarkably persistent.'

One of the things he became very interested in

was the progress of ocean waves, having been generated in a storm

and before arriving at some shore.

-Ah, so he's filling in the middle bit.

-The middle bit, yeah.

-How far they would travel on their own steam, as it were.

-Right.

So from storms that generated the waves off the coast of Antarctica...

-He was trying to follow them?

-He followed them, yes.

There are six stations off the coast of Antarctic,

they went up past New Zealand and then past Samoa, Hawaii.

Each of these measuring stations were a few thousands of miles from the last one.

In the North Pacific - the last of their measuring stations -

since there was no island there they used this boat known as FLIP.

-No, you're kidding me!

-And it does actually flip!

It was like a Thunderbirds-type thing.

Only the Americans would come up with a boat like that.

Does it really tip up?

One end of the boat goes into the water and the other end sticks out.

That must be slightly alarming.

The reason for this is that they want to

try and get the boat as steady as possible

when there's no land to tether it to.

And the way to do that is to kind of anchor the boat in the water.

-Deeper down.

-Deep down, below the motion of the waves.

So it's like sticking a big pendulum...

the weight's at the bottom so is going to be fairly steady.

-Yeah.

-That's clever.

-The depth...

I don't think I'd have liked to be on that boat though.

I mean, you'd be in the middle of the sea and it'd starts tipping up.

-You've got to make sure you tell everybody when you're going to tip it. Very important.

-My God!

And did it work?

Yes, they were certainly able to measure them there

and that was quite late on in the progress of the waves.

-And where would they end up?

-They eventually ended up on the coast of Alaska, having...

-The coast of Alaska, all the way from Antarctica?

-Yeah.

It was a 7,000 mile journey. Astonishing, really.

How does he know that they're the same waves?

Well, that was really the tricky part of the study.

It was all to do with knowing what they were looking for

so the work that had been done during the war

for measuring how waves develop and change with distance from the storm

was crucial in this.

Because that told them what size the waves ought to be

by the time they reached this area.

And remember, once those waves reached the shore of Alaska

at the far end of this journey,

which took them, incidentally, about two weeks to make this journey...

-7,000 miles in two weeks?!

-Yeah.

-That's moving along.

They do, don't they, yeah.

But once they reached the other end,

the energy has been spread in this fan-like way over such a large area

that the wave is very, very small by the time they reach it -

just a matter of millimetres in height.

So by the time it gets to Alaska, it's very shallow but...

Very, very broad.

Munk was the first man who actually thought to follow waves

and find out what happened to them.

He followed them over 7,000 miles, an absolutely epic piece of work.

But what he didn't look at was what happened to waves when they come to the end of their life cycle.

When they arrive at the other edge of the sea.

For thousands of miles,

a wave has a perfectly regular undulating shape.

Then as the wave nears the shore,

it rears up into a crest just before it breaks.

Something has caused it to change.

Essentially what happens is, as it comes in towards the shore,

it feels the presence of the beach that much more

and there is suddenly a great difference between what is happening at the top of the wave

and what is happening at the bottom of the wave.

Theoretically, what that does is

the wave at the top wants to move faster than the wave at the bottom

and that's what causes this over-turning.

Because the speed of the wave is dependent upon the depth.

For the most part, out in the ocean,

the depth is so deep that it's all moving at the same speed.

But when you come towards the shore...

The bottom slows down for some reason.

So the bottom has such an impact all of a sudden

that the change in the height is crucial.

'I was curious to see what happens

'when the energy of a wave dissipates,

'with the help, once again, of Professor McIntyre's rubber ducks.'

So down there it's mostly the energy which is moving?

Well, the energy is going much faster.

-See how much faster the crests are than the ducks?

-Yes.

That slow drift will take them close to the beach

and watch carefully from now on...

That green duck - look.

Suddenly, it gets swept all the way up to the beach.

That's where the wave motion becomes, as it were, water motion or energy propagation.

So when it curls over there,

it ceases to be just the energy that's moving

and the water does actually move?

Is it basically that you are trying to conserve the energy?

The energy has to go somewhere and it has to grab the water, basically?

Not much energy reflects back out.

So most of it has to accumulate

and that's why you get the sudden violence of the wave breaking.

Look at that. I love that.

It's a wonderful visualisation

-of gentle wave motion becoming violent wave motion.

-It is.

You can suddenly, from up there, see it get vertical and then falls over.

-Yes.

-I always think waves are a bit like a man carrying a heavy weight that you tip forward.

He can keep going.

He can keep carrying the weight as long as he keeps going forward.

But if he ever has to stop...

Splat!

It's a law of the universe that energy cannot be destroyed

so as the wave reaches the shore, its energy has to go somewhere.

There are a surprising number of options.

There it is, it's travelled all the way across the Atlantic, happily minding its own business.

It gets to the beach and if it was sentient it would be going,

"Oh, my God, we're running out of water!"

Well, it has to do something different, hasn't it?

Yes, it has to do something.

You cannot make the energy vaporise. So it's going, "OK lads, what do we do now?" There's no water left!"

Things are changed. The energy is experiencing something different when it reaches this region here.

-So what does it do?

-Well, it breaks.

-Right, so that uses some of the energy.

-Yes.

And you see all of the foam

and you hear the noise of the waves breaking -

that's more of the energy.

You're just dissipating energy.

And then presumably, it thumps down onto the sand and that uses a bit?

Exactly, so the sand will absorb energy,

there'll be friction associated with moving the sand.

-It shifts tonnes of sand along with it.

-Exactly.

That takes an awful lot amount of energy as well.

Each individual wave was born thousands of miles away,

travelled across the ocean,

and breaks on the shore in a chaotic confusion of energy and mathematics.

In that moment, the wave dies and the energy moves on...

..as heat from friction,

as shifting sand and kinetic energy,

and sound energy from the bubbles.

I wonder if the energy that powers a wave

is similar to the energy that keeps us alive?

Think of the boat on the sea.

The boat is an object that doesn't change.

The waves upon which it rides are nothing but change.

The continued existence of the boat depends on it resisting change.

The continued existence of the waves are that they continually change.

Now think of the man on the boat.

Which one is he most like?

'If you look at a human being, is a human being an object or a process?'

Or do you even buy the distinction?

I would buy the distinction.

It corresponds to different points of view you can naturally have.

I think a body - the man, of course -

is an organism, is a living thing.

So it is something that is a process

because it has to constantly exchange energy, material,

with the environment in order to persist.

I mean, we are constantly feeding, we have metabolism

and of course, we're exchanging all our atoms.

But still we are maintaining our shape

and we can recognise after ten years that we are the same kind of person.

And the same of course holds in a sense for the wave.

I am 48 years old

and there are few atoms inside me

that I would've possessed when I was born.

The oxygen, water and food we consume is all borrowed.

In the same way, an ocean wave borrows the water it passes through.

This idea of human life as a dynamic process intrigues Raymond Tallis,

former professor of geriatric medicine, poet and philosopher.

Do you think that the reason that

making a metaphor between human beings and waves has a believability about it

is that we're not finished objects, we're kind of in flux?

I mean, you can't make much metaphor out of a human being and a cup

because it's finished, there's nothing else happening.

Whereas, with a wave you can.

I think that's profoundly true, actually.

It seems to me that a wave is only completed when it's destroyed

and a life is only completed, in a sense, when it's destroyed.

What is arrival for a wave?

It either bumps into a barrier, in which case it bounces back

and continues or it's dissipated.

It breaks and it's gone.

And it seems to me that the arrival for a wave...

well, the arrival for a life, is dissipation.

Right. It's building up to that?

Yes. That's a bit pessimistic, isn't it?

One mustn't take it too tragically, I guess.

How do you think about your own mortality?

Well, I'm not in favour of it.

It seems to me that it is obviously the central fact of our lives,

that they are finite.

But the fact they've been produced by processes

means that they're going to be

destroyed by processes. Those who live by the laws of physics,

die by the laws of physics, basically.

And then for that reason,

one has to accept it with as good a grace as possible.

At death, the energy that has kept us alive

leaves us as heat and entropy.

I believe that this dissipation of energy at the end of life

is equivalent to the breaking of a wave.

If you've ever seen the moment of death,

it's a very strange thing.

One minute, there's an energy there, and then its gone.

Nothing else has changed, and yet everything has changed.

Because the energy that WAS that person has moved on.

It's easier to consider death as a necessary evil

if you think through what would happen if our lives never changed.

Imagine your perfect day,

where everything is exactly as you want it to be.

Now imagine it repeated the next day.

And the next and all the next week.

How long would it be before your perfect timeless paradise

became absolutely hellish and you wanted out?

You see, we want that process of change.

Think of it this way - would you really want to be able

to keep your parents forever and never having them die?

But the cost would be you could never have any children.

We don't want that, we are transitory beings.

We want the joy of the new, and the cost is, we have to let the old go.

My mother and father have been coming to this spot

ever since I was born

to look at the ruined priory nearby

'and to watch the waves.'

I was just thinking how I must have been, what,

two and half the first time I went to the priory.

-Two and half?

-Don't you think?

-Really.

-Oh, yeah. I used to take you down there.

I remember feeling the railings being quite rough,

and you'd stand there and you'd kind of see the wave coming in.

And you'd see it coming...!

'A few months after we filmed this scene, my mother died.'

'I've actually got lots of photographs of my mum,

'but the only film I have of her we shot for this film,'

and I decided to film her because I realised it was maybe my last chance

because she was dying.

'I realised even as we were filming it'

that there I was making a film about how things are transitory,

and how things have to move on,

and yet here we were taking a photograph of her,

taking a film of her so that somehow I could hold that moment.

Illogical as I knew it was, I still wanted to do it.

'And so it's just the way it's worked out that this film'

and the priory and the waves

have all become inextricably linked for me.

Perhaps I could add something. There is also the compensation of death,

which is to say, without a conclusion there is no sense of form.

There is no sense of rounded meaning.

In many ways, meaning itself cannot be...boundlessly open.

We need closure. We need narrowing. We need sealing off to some extent.

A piece of music would not be enjoyable if went on forever.

And that's why an endless succession of waves, all identical,

would not be very attractive,

however individually beautiful the waves were.

You have to have inflection. When we listen to a clock,

we don't hear "tick tick tick tick". We hear "tick-tock tick-tock",

as if we have to divide in something into a beginning and an end

just to give us some sense of structure and closure.

What's come out of this film for me is I started out thinking

there was this beautiful poetic metaphorical connection between

waves as a process and us and our transitory lives.

I was sure that that was important, but I thought in a poetic way.

What I've learnt is that it's not just poetry,

It's not just a metaphor,

that just as it is the energy in a wave which

forces all of the atoms of the water

into that beautiful and unlikely shape of a wave,

so in us, it's the throughput of energy in our lives which keeps

us and our atoms in this unlikely shape.

And that just as when the energy moves on from a wave and it breaks,

so it is for us.

And so what I've learnt is that

we're not just metaphorically like a wave.

In some really important and scientific way, we ARE a wave.

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