Beyond the Rainbow Colour: The Spectrum of Science

We live in a world ablaze with colour.

Rainbows and rainforests, oceans and humanity -

Earth is the most colourful place we know of.

WHOOPING AND CLAPPING

It's easy to take our colourful world for granted.

"Red", "yellow" and "blue" are some of the first words we learn.

But the colours we can see are only a tiny part of what's out there.

I'm Dr Helen Czerski.

I'm a physicist and, in this programme,

I'm going to take you into the hidden world of invisible colours.

Isn't it fascinating, this view of the world?

Our eyes can't see these colours, yet we've used them

to reveal the secrets of the universe.

When we look at it in infrared, it completely lights up.

We're observing the invisible.

And harness them to look inside ourselves.

But just imagine, back in 1895, seeing this for the first time.

Today these hidden colours are pushing the boundaries

of science and medicine.

We've developed a completely new technology, we can image people.

That's a huge step forward.

In this programme, I'm going to explore the colours

that lie beyond the rainbow and reveal how they'll shape our future.

-CROWD:

-Ten! Nine! Eight!

It's hard not to smile when you're surrounded by colours.

Three! Two! One!

THEY WHOOP

They can transform a run around the park on a wet Sunday.

This is much more fun.

We live our lives in a sea of colour.

They're rushing around us in all directions all the time,

all the colours of the rainbow, and it's only the tiny fraction

that hits the pupil of our eye

that gives us the visual richness of our world.

That richness is all contained in one very familiar pattern.

These are the colours of our rainbow,

from red, orange and yellow all the way through to violet.

But there's more to the world than this.

Off this end of the spectrum is the ultraviolet and X-rays

and gamma rays.

And then down here, past the red,

there's infrared, microwaves and radio waves.

So our part of the spectrum, the bit we see,

this bit in the middle is just a tiny part of a vast range

of colours extending out on either side.

And it really is vast.

Imagine that one of my strides is the entire length

of the visible spectrum, all of the light we can see.

To show the full spectrum, from gamma rays to X-rays

and right through to radio waves, you would need 80 strides...

so the spectrum we can see is only a tiny fraction

of all the light that there is.

Really, a lot of fun. I'd definitely do that again.

And now I need a shower.

The colours we see and don't see all depend on two crucial processes...

..how our eyes take in light

and what our brain does with that information.

And to understand just how fundamental that connection is,

I'm going to turn to something that's got the world talking.

That dress.

This single photograph set the internet alight

with a burning question.

Is this dress blue and black,

or white and gold?

What do you see?

And how is it possible that the person next to you

might see something entirely different?

And this is it, this is the dress from the photograph.

From that photograph, lots of people, millions,

would have said that it was white and gold,

but it clearly isn't.

To find out why our eyes deceive us,

I've come to the University of Newcastle.

Professor Anya Hurlbert is a vision psychologist.

She's interested in why different people

can see the same dress in wildly different colours.

So the dress I'm wearing is very definitely blue and black,

-there's no question about that.

-Yep, I would not argue with that.

Why is there a problem here?

Well, because you know what the lighting is right now,

because you are very used to this, it's completely unambiguous,

but we've recreated the situation of the photograph

in 3D inside my magic tent, my portable lab,

and so I'd like you to enter the tent,

portable lab, face the back wall, so that you can dark adapt.

I need you to just look ahead,

I want your eyes to adjust to the darkness

before I ask you to turn around and have a look at some light.

OK? I think you can turn around now, you're dark adapted enough.

So that dress, it looks to me as though it's white and gold.

I'm very convinced that that is a white and gold dress.

So that dress is the same as the one I'm wearing?

It's exactly the same as the one you're wearing, believe it or not.

And this one, if I look down, this looks blue and black,

but you've changed the lighting here.

I've just changed the lighting on that

and you don't know what the lighting is,

so your brain is interpreting the situation and coming up with

the most plausible explanation for what colour the dress actually is.

And under this situation,

white and gold is one of the most likely possibilities for the dress.

So if we brought different people in here and showed them

exactly the same set-up, people standing next to each other

-would not see the same thing.

-I would predict that, yes.

Open your eyes.

Blue, black.

It's white with gold trim.

-White and gold.

-White and gold?

-Yeah.

White and gold.

I think it's blue and black.

White and gold.

Blue and black.

And so you can't be persuaded?

No, I think it's blue and black.

It's definitely white and gold.

In the cold light of day, there's no mistaking what colour it is.

That was gold and that was white, definitely.

-And what do you see?

-Well, I see blue and black.

They are the same dress. Sorry to tell you this.

It's definitely white with gold, definitely...

and now it isn't.

Something very strange is going on.

Lots of people thought the same.

This animation shows the internet traffic relating to the dress

when the debate reached its peak in February 2015.

Colours are constructed from this extremely variable light signal

that's reflected from the surface of the object.

Daylight has a very regular set of variations.

It varies from a sort of bluish to a yellowish colour.

And then, of course, you have passing clouds

and you have the changing angle of the sun,

so the light that is shining on objects is constantly changing.

Since the light is constantly changing,

we have to adapt our interpretation of colour...

..so we use a trick called colour constancy.

Take a yellow banana, for example.

When it's outside in early morning, soft blueish light,

the light reflected from the banana you'd say is more green.

As you move towards high noon,

the light coming off it will be mostly yellowish light,

and yet you see the banana as yellow

under all those different conditions

because your brain, with its colour constancy mechanisms in-built,

is constantly filtering out the effects

of that varying illumination.

So it's an important assumption our brain is making

-that any given object has one colour, should be one colour?

-Yes.

That is colour constancy. It is the bedrock of colour perception.

The principle of colour constancy explains how we know

that a yellow flower is still yellow,

whether it's in bright sunshine or shade, or lit at noon or sunset.

Would you believe me if I told you

that that dress was exactly the same as the one I'm wearing now?

'But the dress phenomenon showed that colour constancy isn't foolproof.'

In the original photograph, it was very ambiguous as to what

the light sources were shining on the dress.

Some people said, "OK, there's a bit of a bluish light on a white dress

"and that's why it looks blue. It's a white dress."

Other people said, "No, it's mostly lit by a yellow light

"and that's why it looks washed out blue,

"but it's really a dark blue and black."

So the cause of all the arguments about the dress

was that, if you assumed it was lit by blue light,

you saw it as a white and gold dress,

and, if you assumed the lighting was yellow, you saw it as black and blue.

And it all comes down to people's assumptions.

That is an explanation that fits.

So the colours we see are down to how our eyes detect light...

..and how our brain then interprets that information.

Anya's going to show me just how potent

those powers of interpretation are.

-This is a black and white picture of Dunstanburgh Castle.

-Yep.

I'd like to get you to see it in full colour by first adapting

to this false colour image.

What we're trying to do

is adjust the sensitivity of the light receptors in your eye

to the different colours in the image.

By staring at the dot in the middle of the screen, my brain,

and if you try it, your brain, is doing something remarkable.

I need you to keep staring at the central dot,

keep staring at the central dot.

-Keep staring at the central dot.

-DR HELEN LAUGHS

Now, keep staring at the central dot

and now you should see the image in full colour,

-but keep your eyes fixed.

-That's weird!

This is actually the same black and white image you saw before,

but because we've adapted the receptors

in the different parts of your eye,

you're now seeing it in full colour.

I find this absolutely fascinating.

In my head, a full colour image was created of a photograph

that clearly contains no colour.

Our brains are continually adjusting how they process the light

that our eyes perceive,

so that we can see and understand the world in colour.

So we might say that all colour is an illusion.

Some of the best questions in science are deceptively simple

and this is one of them.

Is what you see the same as what I see?

The answer is, it's complicated.

Imagine all the light bouncing around me right now.

Everything it touches is adding something,

taking something away or changing its direction.

There's a huge richness in all that.

And yet our brains are constantly making judgements

and decisions compensating for the complexity,

so that we just get a very simple answer.

An apple that was red this morning is still red this afternoon.

And so I think this dress is brilliant,

because it opens our eyes to the fact that colour is in our minds.

And all of this is just playing with the colours we can see.

The truth is there's far more to colour than meets the eye.

For most of our history we had no idea

there was anything beyond the visible spectrum.

It would take one of the best minds in science to show us

there were more colours out there than the ones we could see.

The man who unlocked this hidden world

lived in this townhouse in Bath.

William Hershel was a talented musician and composer,

but it was his passion for astronomy that would lead

to one of the greatest discoveries in the history of science.

Along with experimenting with telescopes and optics,

he was interested in the nature of light.

He had a theory that different colours of light

might be associated with different temperatures,

so he did an experiment.

Now, when he did it, he used a beam of sunlight coming through

a chink in the curtains and falling onto a table.

We've recreated his experiment,

but we haven't got a nice sunny day and a chink in the curtains.

We've got a supercontinuum laser that generates

all the colours of light that Herschel was using.

In front of his sunbeam, he placed a prism

that split the sunlight into all the colours of the rainbow.

So what he did was put thermometers

in different colours as they lay on the table.

What he found was, at the violet end, there was very little heating

and it increased very gradually towards the red end.

It seemed that different wavelengths of light, different colours,

had different temperatures.

To confirm this was really the case,

Herschel also placed a control thermometer

just beyond the red part of the spectrum,

where there was no colour at all.

He expected this would remain at room temperature...

..but it didn't.

What he saw was that it was those thermometers,

the ones placed beyond the red, that heated up the most.

What this meant was that there was the rainbow we could see,

he called them "the prismatic colours",

but then just beyond the red, there's an extra colour.

It's clearly there, but we can't see it...

..and today we call that colour the infrared.

Herschel's discovery pushed the boundaries

of the light spectrum outwards.

It was no longer limited to the colours we could see with our eyes.

And the hidden world of the infrared is with us all the time.

I've invited some friends to help me explore it.

Using a special camera,

we can convert part of the infrared spectrum into visible colours.

And what we can now see is that hot objects

are constantly giving away energy to their surroundings

in the form of infrared light.

My face and this hot cup of coffee show up as bright orange,

even white if it's really hot...

..while cold objects appear dark blue.

A chilled white wine on the left,

a warm glass of red on the right.

Isn't it fascinating, this view of the world?

It's much more obvious that there's information in it

and it's interesting as well because I tell you what -

you'd never burn your mouth on a hot drink ever again,

cos who would ever drink something that looks like liquid fire?

But this is perfect.

This unusual perspective

demonstrates that colour carries information.

And once you can detect invisible colour,

you can draw a whole new picture of the world.

I'm about to witness some of the most extraordinary new vistas

that the infrared has opened up to us.

This is Nasa's Flight Research Centre in Southern California.

This Boeing 747 may not look particularly unusual,

but it's got something very clever hidden inside.

This plane started life as an ordinary passenger jet,

but these days, it's something really special.

And I'm really excited

because I'm going to get to fly with it on its next mission.

Like any other aircraft, it's going to take off from an airfield

and, like any other jet, it's going to go through the weather

to the top of the first layer of the atmosphere.

But then it's going to keep going,

up into the stratosphere, above almost all the water vapour.

At that point, the back of the aircraft will open up

and what will be revealed is a telescope

capable of looking at the richness of the universe in the infrared,

and I will be closer to the stars than I've ever been in my life.

Meet SOFIA - the Stratospheric Observatory for Infrared Astronomy.

So here we are, ready to go.

There are 25 people on this aircraft.

The crew and the scientists are all back there

doing the last preparations and I'm really excited about two things -

one is that we're going to fly around the back of the planet

in the dark looking out at the universe.

The other one is that I've never had this much legroom

on a flight in my entire life.

-OVER RADIO:

-'45.

'50, valves closed.

'Six-ten.

'Six-ten.

'Ten degrees.'

Right now, we've just left Nevada

and we're just abeam Salt Lake City right now.

So Salt Lake City is right over there?

Salt Lake City is right there.

And you do have the best view on the plane.

It's the greatest view of the world.

This is the best job in the world.

That's the pilot's privilege, isn't it?

-To look out at the sky.

-It is.

The higher we go,

the better the telescope can "see", for lack of a better term,

because there's less moisture in the air the higher we go.

INDISTINCT RADIO CHATTER

We've got the mission director,

so this is the science heart of the mission.

This is where the decisions are being made.

SHE CALLS TO COLLEAGUE

And this is the science ops, the chief scientists,

the people who control the science ops are sitting here.

They're looking right at the telescope.

They've got data on the screens.

You can see the constellations that they're following.

It's the beginning of another long flight

for SOFIA's Science Operations Manager Dr Jim De Buizer.

Tell me why infrared astronomy is worth all of this effort.

There's a lot of dust and gas between us

and a lot of objects of interest.

Stars when they form, for instance,

are completely enshrouded in their natal cocoon of dust and gas.

The infrared allows us to peer into that

and look at what's going on

at the centre of these star-forming regions

and actually find out how these stars form.

I like to use the analogy of a car radio and a GPS.

You can go into a tunnel

and you can't get your GPS to go any more,

but you can get a radio signal

and that's because a radio has a much longer wavelength.

So when we're looking into space,

going for longer wavelengths like the infrared

allows us to penetrate areas

and see things that we can't see in the optical.

We're observing the invisible.

Probing the hidden secrets of the universe

by placing a 17-tonne telescope in the back of a jumbo jet

isn't the easiest thing to do.

Even a tiny bump could blur the image of the sky,

making careful scientific measurements impossible.

The telescope is just behind me on the other side of that blue wall.

It's a big dish and it's pointing out that way into the sky.

The thing is, when we think about telescopes like that,

we think of them being really solid.

They stay in one place on the ground and point at one thing in the sky.

The problem here is it's on a moving plane that's bouncing around

in turbulence and the way it deals with it is really clever.

The telescope is held by motors that are actively adjusting its position

so that it doesn't move relative to its celestial target.

The plane bumps up and down around it, but the telescope stays still.

So even though it looks as though we're moving quite a lot,

SOFIA can stay locked on just one star.

This telescope is using the long wavelengths of infrared

to peer into the inner workings of stars,

opening windows on the universe not available from the ground.

You've got an image here that SOFIA has taken in the past.

This is a picture of the Orion Nebula.

Most of the Orion Nebula is dark

because there is a lot of dust and gas in this nebula.

So what's going on is there are actually a cluster

of very massive stars at the centre of this nebula.

What you are seeing here is not something

that you actually can see in the visible.

What it looks like is empty space,

but when we look at it in infrared, it completely lights up.

So when we look out at the night sky, we assume that when we see black,

it's because there's nothing there, but actually that might not be true.

This is the iconic Horsehead Nebula.

In visible light, it appears to be a black void.

But in the infrared, it's revealed in a whole new light.

Delicate plumes of gas and dust billow through space.

Far from being a beautiful curiosity,

infrared reveals the Horsehead Nebula

for what it really is - an active stellar nursery,

full of the raw materials from which stars are born.

As well as SOFIA, infrared telescopes on satellites in orbit

around the Earth have also sent back spectacular images

of the cosmos that would be invisible to the naked eye.

It's all calmed down now, but it is nearly 4am.

We've been in the air for almost eight hours

and everyone is getting a bit tired.

Part of the reason that this last leg is so long

is that the star they're looking at

is so faint that they need to take pictures of it for three hours

just to gather enough light to get a really good image.

The other thing about this point in the flight, though,

is that because it's near the end, the aircraft isn't carrying much fuel

and that means we're as high as we're going to get.

We're at 43,000 feet, which is just over 13km.

It's the highest up I've ever been in my life.

But we are now on the way home.

Seeing these scientists observe distant stars

during a bumpy night flight in a 747 has been really impressive.

Looking out from the stratosphere

allows SOFIA to capture infrared wavelengths that would never make it

through Earth's atmosphere to the ground,

giving us a whole new perspective on the universe.

It's been a huge privilege to fly on SOFIA.

As we were going, I started to think of her as a flying eye

looking out into the cosmos for all of us.

And I think the real message to take away

is that the dark regions of the night sky may not be dark

if you can look in all the colours that there are.

Because it's not just the infrared -

the palette of the universe has a huge range of colours in it.

And now, as we look out into the universe,

we're starting to paint our picture of it with the full range of colours

that nature has on offer.

Venture further out beyond the infrared

and there are even longer wavelengths.

Microwaves and radio waves.

Invisible light that has given us

our deepest insights into the universe.

Faint signals from the dawn of time itself.

We've harnessed these wavelengths closer to home too,

transforming how we communicate and how we live our lives.

But the story doesn't end there.

After Herschel's discovery of infrared,

the hunt was now on to find even more exotic and bizarre colours.

The obvious place to look was at the other end of the spectrum.

In 1800,

just a year after the discovery of infrared,

German physicist Johann Ritter

found a colour beyond the blue part of the spectrum.

Though we can't see it, we've certainly heard of it.

It's all around us, especially in summer.

That colour is ultraviolet, or UV.

UV has a short wavelength and lots of energy,

which makes it both good and bad for us.

It helps our body produce Vitamin D,

but too much of it can damage our cells and lead to skin cancer.

It's a colour that matters, even if we humans can't see it.

But there are other animals that can.

To begin to explore the hidden world of ultraviolet,

I'm meeting Ron Douglas,

professor of visual neuroscience at London City University.

And some very friendly birds.

We've got starlings here,

who are eagerly pecking away at the food we have got for them.

Starlings have a special relationship with UV.

Their eyes can see this colour

and some of the female birds' feathers reflect it.

I'm intrigued to know why.

They are actually very, very sensitive to UV.

They have photoreceptors that respond in the UV

and they also have lenses at the front of the eye

that let the UV through,

so they really are true experts at UV vision.

And what is it they are looking at, what can they see with UV vision?

SHE LAUGHS

When it comes down to it, for most animals,

life is really about two things -

it's about food and sex.

Perhaps UV-reflecting female starlings

are attractive to male starlings,

cos female UV-reflecting starlings, they have much bigger brood sizes,

they are more effective at having young,

so that must mean they are more effective

at attracting the male starling.

We've got a mixed group around us, both males and females.

I can't tell the difference between them just by looking at them.

Some of the bits of their feathers reflect ultraviolet light.

Of course, we're completely unaware of that.

But they are attracted, in part, to the ultraviolet colours.

So there is no excuse at all for thinking that the world

is the way we humans see it and that we have the best vision of all.

No, absolutely.

In most respects, we have inferior vision to a lot of animals,

so we've seen that we don't see ultraviolet light,

but a lot of animals do.

In fact, for every aspect of vision,

you can pick out an animal and it does it better than us.

One creature that's long had a reputation

for superb eyesight is the eagle.

Meet Sasha.

Well, we've got a... EAGLE SCREECHES

..quite a noisy eagle here. He's talking away to us.

And he's having a good look at everything,

but he's not seeing the world in quite the same way that we are.

What's different about his vision?

His ability to see detail is about twice as good as ours.

It's like having more pixels in your camera.

The more pixels, the higher the quality of the image.

Until recently, it was generally thought that all birds of prey

had UV vision and that this made them better hunters.

There was a very nice story going around that raptors in general

could follow the urine trails laid down by small mammals.

Since urine reflects ultraviolet light,

it was thought that raptors could probably find voles

by following the UV reflecting from urine trails.

Sadly, that seems not to be true

and it's not really true that he doesn't have the photo receptors

to see ultraviolet light, but he actually puts a filter in his lens

that cuts out most of the ultraviolet light.

On the face of it, ultraviolet sounds as though it should be

extremely useful to a top predator...

..but there's a reason Sasha doesn't make use of it.

The one thing we do know about birds of prey

is that they have amazingly keen eyesight.

They are really good at seeing fine detail.

Now, a problem with ultraviolet light

is it's scattered more than other wavelengths,

so ultraviolet light gives you poor images.

As a bird of prey, the last thing you want when hunting small animals

is a lot of scattered light and a blurry image.

And that's why Sasha has a lens over his eye

that filters out the unhelpful ultraviolet.

We humans have also evolved to filter out UV,

both for visual acuity and protection.

But there are other animals which are not privileged

with very sharp vision.

Take the honeybee.

It doesn't see a clear view of the world at all,

but it can see ultraviolet and that gives it a huge advantage.

How is it determined which animals can use which colours?

Well, really, you have to look at it rather differently and think,

"What does the animal actually use its eyes for?"

What is the difference between what a bee has to see

and what a bird of prey has to see and what a songbird has to see?

The bee needs to find the flower with the nectar.

The flower needs to attract the bee to pollinate it.

To discover how they use UV to do it,

I need to see the world the way the bees do.

So how is this camera going to help us?

This camera will show us

the parts of the spectrum that the bee can see, but we can't see,

so it'll show us the bees' hidden world, if you like.

This is the ultraviolet world that the bee has access to.

At every turn there are hidden signs and codes.

What I can see is that these flowers

have really dramatic patterns on them.

That just looks yellow here.

Absolutely, but it's rather confusing.

If you can't see, or if you just saw plain yellow,

you would actually be hard-pushed to know where the nectar was.

It would be really useful to have a signal,

like guiding lights, to show you where the nectar is.

Kind of like arrows, saying, "Nectar here".

Seen in ultraviolet, some flowers do exactly that.

To the bees, these UV signals are like advertising hoardings

highlighting where the nectar and pollen are.

These markings are caused by pigments in the flower called flavonoids,

some of which are visible in the ultraviolet.

It's a world of patterns

and shapes that's completely hidden from our eyes.

The bee gets by without much detail.

Being able to see UV allows it to find the right flowers

and get back to the hive with its precious cargo

as quickly as possible.

And so this is all about survival?

It is. You have eyes that serve your needs, basically.

We're still only just beginning to appreciate the hidden world

of the ultraviolet and its vital role in nature.

Yet even this isn't the end of the spectrum of colours

that come from the sun.

Beyond ultraviolet is a final swathe of hidden colours

that perhaps have the greatest potential to shape our future.

We can't see inside our own bodies

and, on a daily basis, most of us really wouldn't want to.

But just imagine, back in 1895,

seeing this for the first time.

It's the first ever X-ray, it was taken by Wilhelm Rontgen,

and the picture is of his wife's hand.

You can see the bones in her fingers and her wedding ring here.

This was a shocking image because,

up till then, skeletons were only ever seen after you were dead.

Rontgen's wife was well aware of that. She was horrified.

She said, "I have seen my own death."

Rontgen called these mysterious rays "X-rays"

because he didn't know what they were and the name has stuck.

We now know they're a type of invisible light,

an invisible rainbow of colours,

with a very short wavelength and a very high energy.

High enough to pass through tissue

and reveal the hidden world inside the human body.

But this new colour came at a price.

The early X-ray pioneers were known as roentgenologists

and there was a meeting of them in 1920,

where they met from all over Europe.

They sat down to dinner, a chicken dinner,

but almost none of them would be able to eat the meal

because almost none of them would be able to cut the meat,

because they were missing fingers and hands from radiation damage.

Today, we understand much better the dangers posed by radiation.

Doctors still rely on Roentgen's X-rays

as a powerful diagnostic tool.

Thanks to new technologies, we can even use them to create

detailed images of our bones and joints while they're moving.

It's a bit like an X-ray movie,

allowing surgeons to see what's really going on inside us.

This invisible colour can reveal the hidden world of the human body

at the scale of bones and joints.

But if you want to see something smaller,

to probe the very structure of matter itself, you soon hit a problem.

The visible light all around me has a tiny wavelength,

the distance between two peaks of the wave

is less than a thousandth of a millimetre.

That is fine for seeing things that are bigger than that wavelength,

but anything smaller is a problem

and atoms are a thousand times smaller again.

There is a way around this problem,

but as is often the way with physics,

the smaller the thing you're looking at,

the bigger your piece of kit needs to be.

And they don't come much bigger than this.

It may look like a giant spaceship that's landed

in the Oxfordshire countryside, but it's actually a synchrotron.

It's a huge circular machine capable of generating light

that's ten billion times brighter than the sun...

..including high-energy X-rays

that can reveal the hidden wonders of the world at the microscopic scale.

I won't ever directly see the molecules that are keeping me alive

because the colours I can see

and the way that I see just can't touch that level of detail.

But here they can watch a single colour

ripple through a giant molecule and look at the patterns you get

when light interacts with matter,

and they're so sophisticated at that that they can visualise

on an atomic scale the architecture of life.

The Diamond Light Source synchrotron works like a giant microscope,

producing invisible wavelengths of light of extremely high energy.

So would you come down here very often?

Generally, generally, we don't....

'This invisible light is used by scientists like Dr Anna Warren

'to probe a world so tiny

'that it was beyond our reach until very recently.'

So this is called the storage ring

and what's happening in here is the electrons are spinning round

the circumference, which is about 562 metres.

The electrons are going almost the speed of light

so they're going really, really fast.

As the electrons race around the storage ring,

powerful magnets alter their direction,

causing the electrons to release energy in the form of X-rays.

The only reason we can stand here now

-is because this isn't switched on, right?

-Yep.

We definitely wouldn't want to be in here

when the electron beam was running round.

The synchrotron can produce invisible colours

of such high energy and such short wavelengths

that they can penetrate the molecules

that make up the world around us

and reveal their shape and structure.

It's a technique that has its roots in the 1950s,

when Rosalind Franklin famously used X-rays to unlock the shape

of the most celebrated molecule in the history of science -

the double-helix structure of DNA.

Today, the focus of this type of research is proteins,

the most crucial cogs in the molecular machinery of life.

They carry out nearly all the vital processes

that keep living organisms ticking along.

For every protein, shape is key to its function.

It's only when we can see the details of a protein's shape

that we can really understand how it works.

So we've got an example up here of a protein, so...

-That looks like tangled knitting.

-Yes.

But you can see that it's a very complex structure,

but we might be able to understand certain pockets within here,

like this dip here.

Knowing the shape, we might be able to say,

"Oh, look, there's an area here or an area here

"that may interact with something in our body."

It was in 1965 that scientists, using X-rays,

first deduced the shape of a specific type of protein called an enzyme.

It came from the humble egg.

Known as lysozyme, it's an antibacterial enzyme

which keeps eggs bug-free, even when you don't keep them in the fridge.

But you can't just X-ray an egg to reveal the shape of lysozyme.

You first need to grow lysozyme molecules into a crystal.

A crystal is not something I associate with an egg.

No. So the crystal is really key to the experiment.

So we're forcing the protein molecules

to pack in a very regular manner,

so we'll have protein molecules extending in three dimensions.

It has to be very regular

and it forms these layers within the crystal.

It's these layers that then interact with the X-rays

and allow us to get information about the structure.

What's so crucial about crystals is that the molecules within them

are arranged in a highly regular, repeating pattern.

And it's only when the molecules are in this form

that the invisible X-rays can reveal their secrets.

The technique is known as X-ray crystallography

and it's the same principle that Rosalind Franklin used.

The way you get from the structure of a crystal to a pattern

is really clever, it's a nice little bit of physics called diffraction.

On the end of the ruler here, there are lots of black lines

and, on this side, they're inches,

so they're divided up into tenths of an inch,

and I've got a laser pointer here which is shining at those

and it's reflecting off each of the gaps in-between the markers.

So this is like X-ray light coming in and reflecting off

each of the crystal layers, each of those plains within the crystal.

And if I switch on my laser pointer,

what I can see on the wall over there is a pattern of dots

and they're very evenly spaced.

There's a strange thing about this -

you can see that the dots are quite close together.

And the lines on the inches side here are quite far apart.

If I move the ruler across to the other side...

..the millimetre marks are much, much closer together

and the dots on the wall have got further apart.

So the weird thing about diffraction is the way that these waves work

is that the closer together your plains are,

the further apart the spots are.

Today, despite having a synchrotron at her disposal,

Anna still has to turn any molecule into a crystal

before she can work out its shape.

First, she chooses the best crystal.

It takes a steady hand to retrieve it.

A robot arm picks up the crystal

and places it in front of the X-ray beam.

To work out the shape of the molecule,

we look in more detail at what we call the intensity of the spot,

so we're looking at whether this spot is brighter than this spot.

Very quickly, we can obtain information about the size

of the molecules from looking at the spacing between these spots.

By analysing the exact position and intensity of these spots,

Anna can work out the location of every atom.

This allows her to construct a three-dimensional image

of some of the most complicated structures in nature.

So this is the structure that we've obtained from the lysozyme crystals.

So you can see it is quite a complex molecule

and you can see all the atoms packing together

into this three-dimensional shape.

We can rotate the molecule round and you can get an idea about

the full three-dimensional shape of it.

The mystery of lysozyme's structure can only be solved

with the help of invisible colours like X-rays.

They help us resolve not just the fine details of the molecule's shape,

but also how they work.

This cleft area is where the lysozyme grabs hold of bacteria.

X-ray diffraction shows that once it has grabbed the bacteria,

the cleft subtly changes shape,

breaking the bacterial cell wall and ultimately killing it.

That isn't just crucially important for keeping eggs fresh.

Lysozyme is also a vital component of our immune system.

I mean, it's a very exciting process,

when you've spent years trying to crystallise it

and then you can see your structure on the screen.

People don't mind spending years doing it,

because once you get that information,

there's so much you can do with it.

It can help numerous groups

to help develop medicine and vaccines and things.

The sheer size of the synchrotron

means it can produce a vast range of intensities

and wavelengths of light.

The shorter the wavelength, the higher the energy

and the smaller the world you can probe.

It's enabled the synchrotron

to penetrate the hidden structures of matter,

allowing us to achieve medical breakthroughs,

build ever-shrinking machines and design new wonder materials.

The knowledge that flows from this technology

is allowing us to understand the world as never before,

pushing back the boundaries of science.

The entire spectrum of colours is vast and fascinating.

It allows us to see everything from the building blocks of life

to the furthest stars and galaxies.

It's this ability to harness the invisible

that's allowed us to see so much more of the world

than our own eyes can perceive.

And now, scientists are starting to use the properties of colour

to do something that will have perhaps the most profound impact

on our lives in the future...

..to see inside the human body

in a way that's never been possible before.

Professor Mark Lythgoe from University College London

is at the cutting edge of this new frontier of colour.

This is the exciting new world of biomedical imaging.

The body is a real challenge. It's a complete black box.

There is no light in there

and somehow we've got to make the body light up.

Mark's way of doing this sounds a little bit like science fiction.

He calls it the Invisible Man Project.

Over here is a sample from a heart.

Hold that.

I think most people know that tissue inside our bodies

is a pink-y, pale pink-y colour apart from things like the liver,

which are really darkly brown.

-This is the magic behind it.

-OK.

If I can get you to hold this.

-It's a bit slippery.

-Yeah, got it.

And the idea is we make it completely disappear

from the bottom up, I hope.

-SHE LAUGHS

-OK.

Let's see if we can see this.

Mark places a hollow glass tube inside a container of liquid.

-And then watch the bottom....

-Oh, I love this! It's vanishing,

it's vanishing! That's brilliant!

It's brilliant, I love this!

So it's like the tube is just disappearing,

-but the blue stripe's still there.

-Yeah.

So the liquid is filling the tube from the inside

-and wherever it's full, it's just vanished.

-Yeah.

This vanishing trick illustrates an important property of light.

When light passes through a material such as glass,

it slows down and gets bent,

and its path depends on a property called its refractive index.

It's what allows us to see the glass.

If the refractive index of two materials,

like the liquid and the glass, is the same,

light isn't bent at the point where they meet.

Its path is undisturbed as it passes through...

..so we have no way of seeing the glass tube.

That's what we try to do.

We try to match the refractive indexes in tissue

and then, by definition, it should become transparent.

Mark has applied this technique to reveal the hidden colours

of a whole range of human organs.

Certain parts of the body

actually have the potential to give out light.

Your brain, your heart, your liver all fluoresces naturally.

It's called autofluorescence, but, of course, we can't see that light

cos it doesn't get out of the body.

So I'm lit up like a Christmas tree on the inside?

If we could make you completely transparent,

there will be different colours coming out of you.

You'd be fluorescing.

The question is, can we use that information?

By making tissue transparent,

Mark has found a way to use this in-built ability to fluoresce

to do something extraordinary.

This is a piece of liver.

Naturally, the liver fluoresces a sort of bluey-violet colour.

I had no idea, that's brilliant.

The wonderful thing seems to be,

as the tissue changes from normal tissue to diseased tissue,

and, in this case, these are tiny cancers

that are scattered throughout the liver.

And for some reason, and we're not too sure of this yet,

they give out a different colour light,

so we can discriminate normal tissue from diseased tissue

just by looking at the natural colours that the body gives out.

The blue colour is the normal, healthy liver

and anything that's gold shows the cancerous cells of a tumour.

-So the body is doing the work for you here?

-Completely.

You don't have to add anything?

That's right, all you need to do is tap into it.

The trick is you have to make the body invisible.

Mark's technique uses light and colour

to highlight the cancerous cells.

So far, it only works on dead tissue.

So the next challenge is to see inside the body

while it's still alive.

To achieve this,

Mark is developing a radical new technique that could allow us to see

the colour of living body tissues while they're still inside us.

There is a wonderful effect called the photoacoustic effect

and, to some degree, its...

"Remarkable" would perhaps be an understatement for it.

You can shine light into the body

and that light is then converted into sound.

We measure the sound, or listen to the sound as it comes out

of the body, and that tells us about how the body is working.

To see this process in action,

I have to place my hand in the path of a rather powerful laser.

So this is all about pigments.

Think about pigments in the body,

but it's a different way of thinking about coloured pigments.

Pigments have more to offer than their colour.

Haemoglobin is one of our body's most important pigments,

and it's responsible for picking up oxygen molecules

and carrying them round our body.

But it's the rich red colour of oxygenated haemoglobin

that's crucial to Mark's cutting-edge imaging techniques.

So the red laser goes in and it's absorbed by certain pigments

and inside the blood vessels there are blood cells,

and inside that there are pigments.

They wonderfully absorb red light

and, as they do, they just heat up a tiny bit.

As they do, they give out a tiny sound wave.

The light comes in, the sound comes out,

so we create a three-dimensional map of the blood vessels

by listening to the sound as it comes out of the red blood cells.

The haemoglobin in my body tissues absorbs specific colours of light

and, even though it only heats up by a minuscule amount,

it expands quickly enough to send out detectable sound.

The surrounding tissue doesn't absorb the colours to the same degree

and so returns a far weaker sound signature.

By using sound to measure these tiny differences in colour absorption,

Mark can create a 3D image of the blood vessels inside my hand.

Right on the surface are these tiny lines

that you can see running through there,

just there as they come round, like a grid pattern.

Those are the fingerprints that are on the surface of the skin

and, within them, they contain pigments.

Melanin. So when you have a mole on your hand

and it goes slightly brown, that's a pigment.

That brown pigment.

There are tiny differences in the pigments in your skin

and that's also absorbing that red light

and then expanding and giving out that tiny sound wave.

Without adding or doing anything to you,

we get an instant three-dimensional picture

of the blood vessels in your hand,

and this hasn't been done before.

So, by using sound, you can see the colours inside our bodies

that our eyes can't?

Completely.

By shining coloured light into tissue,

and then converting that light into sound,

the inside of my hand is revealed in exquisite detail.

The thing that strikes me about this is that you've found a way

to light up different systems of the body in different colours,

so blood can be one colour and the tumour cells can be different colour,

so you can separate out all those things in different colours

-and see the body in a completely different way.

-Yes.

It's about the pigments, it's about the colours.

Once you understand colours, then you can understand

whether they're going to absorb light or reflect it.

So where is this going in the future?

As we've seen today, we've taken your hand

and we've put it into the system.

We can image people - that's a huge step forward.

We've developed a completely new technology,

that's out there now in several labs,

and we're starting to use it on people.

The next stage is to get it into hospitals.

There's more than one way of looking at a human.

Mark Lythgoe and his team are pioneering the ways

that we will see ourselves in the future

and with that will come new medical insights

and new ways of detecting and treating disease.

The human body is possibly the thing that's most familiar to us

and it's shared by all the humans in history.

Plato and Shakespeare and Queen Victoria

all had a body with the same basic physiology

and these new imaging techniques are letting us see that body now

in a whole new light.

This series has taken me

on a journey through the story of our world in 15 colours.

I've explored where colour comes from,

why our planet is the most colourful place we know of,

how colour has shaped the living world,

and how it will mould our future.

I had a paint box when I was a child,

all the colours laid out on the grid, and they were so easily accessible.

All I needed to paint the world was a paintbrush and some water.

And now, when I look at a paint box like that, I see so much more.

In red, there's the history of the early earth.

And in green, there's a colour that's working around us

all the time, harvesting sunlight.

And in violet, there's a reminder of the colours beyond the rainbow.

Sometimes it's the simplest things in life

that tell the richest stories

and to appreciate the stories of colour,

all you need to do is walk out into the world and look.

Discover more about the story of the colours of scientific discovery

with the Open University.

Go to...

..and follow the links to the Open University.