0:00:03 > 0:00:07We live in a world ablaze with colour.
0:00:07 > 0:00:11Rainbows and rainforests, oceans and humanity -
0:00:11 > 0:00:14Earth is the most colourful place we know of.
0:00:14 > 0:00:17WHOOPING AND CLAPPING
0:00:17 > 0:00:20It's easy to take our colourful world for granted.
0:00:20 > 0:00:23"Red", "yellow" and "blue" are some of the first words we learn.
0:00:23 > 0:00:28But the colours we can see are only a tiny part of what's out there.
0:00:29 > 0:00:31I'm Dr Helen Czerski.
0:00:31 > 0:00:34I'm a physicist and, in this programme,
0:00:34 > 0:00:39I'm going to take you into the hidden world of invisible colours.
0:00:39 > 0:00:41Isn't it fascinating, this view of the world?
0:00:41 > 0:00:45Our eyes can't see these colours, yet we've used them
0:00:45 > 0:00:47to reveal the secrets of the universe.
0:00:47 > 0:00:50When we look at it in infrared, it completely lights up.
0:00:50 > 0:00:52We're observing the invisible.
0:00:54 > 0:00:56And harness them to look inside ourselves.
0:00:57 > 0:01:02But just imagine, back in 1895, seeing this for the first time.
0:01:03 > 0:01:07Today these hidden colours are pushing the boundaries
0:01:07 > 0:01:08of science and medicine.
0:01:09 > 0:01:14We've developed a completely new technology, we can image people.
0:01:14 > 0:01:16That's a huge step forward.
0:01:16 > 0:01:19In this programme, I'm going to explore the colours
0:01:19 > 0:01:24that lie beyond the rainbow and reveal how they'll shape our future.
0:01:35 > 0:01:39- CROWD:- Ten! Nine! Eight!
0:01:39 > 0:01:43It's hard not to smile when you're surrounded by colours.
0:01:43 > 0:01:45Three! Two! One!
0:01:45 > 0:01:48THEY WHOOP
0:01:48 > 0:01:52They can transform a run around the park on a wet Sunday.
0:01:52 > 0:01:53This is much more fun.
0:01:55 > 0:01:58We live our lives in a sea of colour.
0:01:58 > 0:02:01They're rushing around us in all directions all the time,
0:02:01 > 0:02:04all the colours of the rainbow, and it's only the tiny fraction
0:02:04 > 0:02:06that hits the pupil of our eye
0:02:06 > 0:02:09that gives us the visual richness of our world.
0:02:11 > 0:02:15That richness is all contained in one very familiar pattern.
0:02:17 > 0:02:19These are the colours of our rainbow,
0:02:19 > 0:02:23from red, orange and yellow all the way through to violet.
0:02:23 > 0:02:25But there's more to the world than this.
0:02:25 > 0:02:29Off this end of the spectrum is the ultraviolet and X-rays
0:02:29 > 0:02:30and gamma rays.
0:02:30 > 0:02:32And then down here, past the red,
0:02:32 > 0:02:36there's infrared, microwaves and radio waves.
0:02:36 > 0:02:39So our part of the spectrum, the bit we see,
0:02:39 > 0:02:44this bit in the middle is just a tiny part of a vast range
0:02:44 > 0:02:46of colours extending out on either side.
0:02:48 > 0:02:51And it really is vast.
0:02:51 > 0:02:54Imagine that one of my strides is the entire length
0:02:54 > 0:02:58of the visible spectrum, all of the light we can see.
0:02:59 > 0:03:03To show the full spectrum, from gamma rays to X-rays
0:03:03 > 0:03:08and right through to radio waves, you would need 80 strides...
0:03:08 > 0:03:12so the spectrum we can see is only a tiny fraction
0:03:12 > 0:03:14of all the light that there is.
0:03:14 > 0:03:18Really, a lot of fun. I'd definitely do that again.
0:03:18 > 0:03:19And now I need a shower.
0:03:25 > 0:03:30The colours we see and don't see all depend on two crucial processes...
0:03:32 > 0:03:34..how our eyes take in light
0:03:34 > 0:03:36and what our brain does with that information.
0:03:38 > 0:03:42And to understand just how fundamental that connection is,
0:03:42 > 0:03:45I'm going to turn to something that's got the world talking.
0:03:47 > 0:03:48That dress.
0:03:48 > 0:03:51This single photograph set the internet alight
0:03:51 > 0:03:53with a burning question.
0:03:54 > 0:03:57Is this dress blue and black,
0:03:57 > 0:03:58or white and gold?
0:03:59 > 0:04:01What do you see?
0:04:03 > 0:04:05And how is it possible that the person next to you
0:04:05 > 0:04:08might see something entirely different?
0:04:10 > 0:04:13And this is it, this is the dress from the photograph.
0:04:13 > 0:04:16From that photograph, lots of people, millions,
0:04:16 > 0:04:18would have said that it was white and gold,
0:04:18 > 0:04:20but it clearly isn't.
0:04:23 > 0:04:26To find out why our eyes deceive us,
0:04:26 > 0:04:28I've come to the University of Newcastle.
0:04:32 > 0:04:35Professor Anya Hurlbert is a vision psychologist.
0:04:37 > 0:04:39She's interested in why different people
0:04:39 > 0:04:43can see the same dress in wildly different colours.
0:04:43 > 0:04:46So the dress I'm wearing is very definitely blue and black,
0:04:46 > 0:04:49- there's no question about that. - Yep, I would not argue with that.
0:04:49 > 0:04:50Why is there a problem here?
0:04:50 > 0:04:52Well, because you know what the lighting is right now,
0:04:52 > 0:04:55because you are very used to this, it's completely unambiguous,
0:04:55 > 0:04:58but we've recreated the situation of the photograph
0:04:58 > 0:05:00in 3D inside my magic tent, my portable lab,
0:05:00 > 0:05:02and so I'd like you to enter the tent,
0:05:02 > 0:05:06portable lab, face the back wall, so that you can dark adapt.
0:05:06 > 0:05:08I need you to just look ahead,
0:05:08 > 0:05:11I want your eyes to adjust to the darkness
0:05:11 > 0:05:14before I ask you to turn around and have a look at some light.
0:05:14 > 0:05:18OK? I think you can turn around now, you're dark adapted enough.
0:05:24 > 0:05:27So that dress, it looks to me as though it's white and gold.
0:05:27 > 0:05:30I'm very convinced that that is a white and gold dress.
0:05:32 > 0:05:34So that dress is the same as the one I'm wearing?
0:05:34 > 0:05:37It's exactly the same as the one you're wearing, believe it or not.
0:05:37 > 0:05:39And this one, if I look down, this looks blue and black,
0:05:39 > 0:05:41but you've changed the lighting here.
0:05:41 > 0:05:43I've just changed the lighting on that
0:05:43 > 0:05:45and you don't know what the lighting is,
0:05:45 > 0:05:48so your brain is interpreting the situation and coming up with
0:05:48 > 0:05:51the most plausible explanation for what colour the dress actually is.
0:05:51 > 0:05:52And under this situation,
0:05:52 > 0:05:57white and gold is one of the most likely possibilities for the dress.
0:06:00 > 0:06:02So if we brought different people in here and showed them
0:06:02 > 0:06:05exactly the same set-up, people standing next to each other
0:06:05 > 0:06:08- would not see the same thing. - I would predict that, yes.
0:06:12 > 0:06:13Open your eyes.
0:06:14 > 0:06:16Blue, black.
0:06:16 > 0:06:19It's white with gold trim.
0:06:19 > 0:06:20- White and gold. - White and gold?- Yeah.
0:06:20 > 0:06:22White and gold.
0:06:22 > 0:06:24I think it's blue and black.
0:06:24 > 0:06:25White and gold.
0:06:25 > 0:06:27Blue and black.
0:06:27 > 0:06:29And so you can't be persuaded?
0:06:29 > 0:06:31No, I think it's blue and black.
0:06:31 > 0:06:33It's definitely white and gold.
0:06:33 > 0:06:37In the cold light of day, there's no mistaking what colour it is.
0:06:38 > 0:06:41That was gold and that was white, definitely.
0:06:41 > 0:06:44- And what do you see? - Well, I see blue and black.
0:06:44 > 0:06:47They are the same dress. Sorry to tell you this.
0:06:47 > 0:06:50It's definitely white with gold, definitely...
0:06:50 > 0:06:51and now it isn't.
0:06:51 > 0:06:53Something very strange is going on.
0:06:56 > 0:06:58Lots of people thought the same.
0:07:00 > 0:07:03This animation shows the internet traffic relating to the dress
0:07:03 > 0:07:06when the debate reached its peak in February 2015.
0:07:09 > 0:07:14Colours are constructed from this extremely variable light signal
0:07:14 > 0:07:17that's reflected from the surface of the object.
0:07:20 > 0:07:24Daylight has a very regular set of variations.
0:07:24 > 0:07:27It varies from a sort of bluish to a yellowish colour.
0:07:31 > 0:07:34And then, of course, you have passing clouds
0:07:34 > 0:07:36and you have the changing angle of the sun,
0:07:36 > 0:07:40so the light that is shining on objects is constantly changing.
0:07:43 > 0:07:45Since the light is constantly changing,
0:07:45 > 0:07:48we have to adapt our interpretation of colour...
0:07:49 > 0:07:52..so we use a trick called colour constancy.
0:07:53 > 0:07:56Take a yellow banana, for example.
0:07:56 > 0:08:00When it's outside in early morning, soft blueish light,
0:08:00 > 0:08:03the light reflected from the banana you'd say is more green.
0:08:03 > 0:08:05As you move towards high noon,
0:08:05 > 0:08:08the light coming off it will be mostly yellowish light,
0:08:08 > 0:08:09and yet you see the banana as yellow
0:08:09 > 0:08:11under all those different conditions
0:08:11 > 0:08:15because your brain, with its colour constancy mechanisms in-built,
0:08:15 > 0:08:17is constantly filtering out the effects
0:08:17 > 0:08:19of that varying illumination.
0:08:19 > 0:08:21So it's an important assumption our brain is making
0:08:21 > 0:08:25- that any given object has one colour, should be one colour?- Yes.
0:08:25 > 0:08:29That is colour constancy. It is the bedrock of colour perception.
0:08:31 > 0:08:35The principle of colour constancy explains how we know
0:08:35 > 0:08:37that a yellow flower is still yellow,
0:08:37 > 0:08:43whether it's in bright sunshine or shade, or lit at noon or sunset.
0:08:44 > 0:08:46Would you believe me if I told you
0:08:46 > 0:08:50that that dress was exactly the same as the one I'm wearing now?
0:08:50 > 0:08:55'But the dress phenomenon showed that colour constancy isn't foolproof.'
0:08:55 > 0:08:58In the original photograph, it was very ambiguous as to what
0:08:58 > 0:09:00the light sources were shining on the dress.
0:09:00 > 0:09:04Some people said, "OK, there's a bit of a bluish light on a white dress
0:09:04 > 0:09:06"and that's why it looks blue. It's a white dress."
0:09:06 > 0:09:09Other people said, "No, it's mostly lit by a yellow light
0:09:09 > 0:09:11"and that's why it looks washed out blue,
0:09:11 > 0:09:13"but it's really a dark blue and black."
0:09:13 > 0:09:16So the cause of all the arguments about the dress
0:09:16 > 0:09:19was that, if you assumed it was lit by blue light,
0:09:19 > 0:09:22you saw it as a white and gold dress,
0:09:22 > 0:09:26and, if you assumed the lighting was yellow, you saw it as black and blue.
0:09:26 > 0:09:28And it all comes down to people's assumptions.
0:09:28 > 0:09:30That is an explanation that fits.
0:09:31 > 0:09:35So the colours we see are down to how our eyes detect light...
0:09:37 > 0:09:41..and how our brain then interprets that information.
0:09:43 > 0:09:46Anya's going to show me just how potent
0:09:46 > 0:09:48those powers of interpretation are.
0:09:49 > 0:09:52- This is a black and white picture of Dunstanburgh Castle.- Yep.
0:09:52 > 0:09:55I'd like to get you to see it in full colour by first adapting
0:09:55 > 0:09:57to this false colour image.
0:09:58 > 0:10:00What we're trying to do
0:10:00 > 0:10:04is adjust the sensitivity of the light receptors in your eye
0:10:04 > 0:10:07to the different colours in the image.
0:10:07 > 0:10:10By staring at the dot in the middle of the screen, my brain,
0:10:10 > 0:10:14and if you try it, your brain, is doing something remarkable.
0:10:17 > 0:10:19I need you to keep staring at the central dot,
0:10:19 > 0:10:21keep staring at the central dot.
0:10:21 > 0:10:23- Keep staring at the central dot. - DR HELEN LAUGHS
0:10:23 > 0:10:25Now, keep staring at the central dot
0:10:25 > 0:10:27and now you should see the image in full colour,
0:10:27 > 0:10:29- but keep your eyes fixed. - That's weird!
0:10:29 > 0:10:32This is actually the same black and white image you saw before,
0:10:32 > 0:10:34but because we've adapted the receptors
0:10:34 > 0:10:36in the different parts of your eye,
0:10:36 > 0:10:39you're now seeing it in full colour.
0:10:39 > 0:10:41I find this absolutely fascinating.
0:10:43 > 0:10:47In my head, a full colour image was created of a photograph
0:10:47 > 0:10:49that clearly contains no colour.
0:10:51 > 0:10:54Our brains are continually adjusting how they process the light
0:10:54 > 0:10:56that our eyes perceive,
0:10:56 > 0:10:59so that we can see and understand the world in colour.
0:11:02 > 0:11:05So we might say that all colour is an illusion.
0:11:08 > 0:11:11Some of the best questions in science are deceptively simple
0:11:11 > 0:11:13and this is one of them.
0:11:13 > 0:11:15Is what you see the same as what I see?
0:11:15 > 0:11:18The answer is, it's complicated.
0:11:18 > 0:11:21Imagine all the light bouncing around me right now.
0:11:21 > 0:11:23Everything it touches is adding something,
0:11:23 > 0:11:26taking something away or changing its direction.
0:11:26 > 0:11:29There's a huge richness in all that.
0:11:29 > 0:11:32And yet our brains are constantly making judgements
0:11:32 > 0:11:35and decisions compensating for the complexity,
0:11:35 > 0:11:38so that we just get a very simple answer.
0:11:38 > 0:11:42An apple that was red this morning is still red this afternoon.
0:11:42 > 0:11:44And so I think this dress is brilliant,
0:11:44 > 0:11:49because it opens our eyes to the fact that colour is in our minds.
0:11:49 > 0:11:52And all of this is just playing with the colours we can see.
0:11:53 > 0:11:57The truth is there's far more to colour than meets the eye.
0:11:59 > 0:12:01For most of our history we had no idea
0:12:01 > 0:12:04there was anything beyond the visible spectrum.
0:12:06 > 0:12:10It would take one of the best minds in science to show us
0:12:10 > 0:12:13there were more colours out there than the ones we could see.
0:12:29 > 0:12:31The man who unlocked this hidden world
0:12:31 > 0:12:34lived in this townhouse in Bath.
0:12:40 > 0:12:44William Hershel was a talented musician and composer,
0:12:44 > 0:12:47but it was his passion for astronomy that would lead
0:12:47 > 0:12:50to one of the greatest discoveries in the history of science.
0:12:51 > 0:12:54Along with experimenting with telescopes and optics,
0:12:54 > 0:12:56he was interested in the nature of light.
0:12:56 > 0:12:59He had a theory that different colours of light
0:12:59 > 0:13:02might be associated with different temperatures,
0:13:02 > 0:13:04so he did an experiment.
0:13:04 > 0:13:07Now, when he did it, he used a beam of sunlight coming through
0:13:07 > 0:13:10a chink in the curtains and falling onto a table.
0:13:11 > 0:13:13We've recreated his experiment,
0:13:13 > 0:13:17but we haven't got a nice sunny day and a chink in the curtains.
0:13:17 > 0:13:20We've got a supercontinuum laser that generates
0:13:20 > 0:13:22all the colours of light that Herschel was using.
0:13:24 > 0:13:26In front of his sunbeam, he placed a prism
0:13:26 > 0:13:29that split the sunlight into all the colours of the rainbow.
0:13:31 > 0:13:32So what he did was put thermometers
0:13:32 > 0:13:35in different colours as they lay on the table.
0:13:35 > 0:13:39What he found was, at the violet end, there was very little heating
0:13:39 > 0:13:42and it increased very gradually towards the red end.
0:13:44 > 0:13:48It seemed that different wavelengths of light, different colours,
0:13:48 > 0:13:50had different temperatures.
0:13:52 > 0:13:55To confirm this was really the case,
0:13:55 > 0:13:58Herschel also placed a control thermometer
0:13:58 > 0:14:00just beyond the red part of the spectrum,
0:14:00 > 0:14:02where there was no colour at all.
0:14:04 > 0:14:07He expected this would remain at room temperature...
0:14:08 > 0:14:10..but it didn't.
0:14:11 > 0:14:14What he saw was that it was those thermometers,
0:14:14 > 0:14:18the ones placed beyond the red, that heated up the most.
0:14:20 > 0:14:24What this meant was that there was the rainbow we could see,
0:14:24 > 0:14:26he called them "the prismatic colours",
0:14:26 > 0:14:30but then just beyond the red, there's an extra colour.
0:14:30 > 0:14:33It's clearly there, but we can't see it...
0:14:34 > 0:14:38..and today we call that colour the infrared.
0:14:39 > 0:14:41Herschel's discovery pushed the boundaries
0:14:41 > 0:14:43of the light spectrum outwards.
0:14:44 > 0:14:48It was no longer limited to the colours we could see with our eyes.
0:14:50 > 0:14:54And the hidden world of the infrared is with us all the time.
0:14:57 > 0:15:00I've invited some friends to help me explore it.
0:15:04 > 0:15:06Using a special camera,
0:15:06 > 0:15:10we can convert part of the infrared spectrum into visible colours.
0:15:13 > 0:15:16And what we can now see is that hot objects
0:15:16 > 0:15:19are constantly giving away energy to their surroundings
0:15:19 > 0:15:21in the form of infrared light.
0:15:26 > 0:15:31My face and this hot cup of coffee show up as bright orange,
0:15:31 > 0:15:33even white if it's really hot...
0:15:36 > 0:15:38..while cold objects appear dark blue.
0:15:41 > 0:15:44A chilled white wine on the left,
0:15:44 > 0:15:46a warm glass of red on the right.
0:15:48 > 0:15:50Isn't it fascinating, this view of the world?
0:15:50 > 0:15:53It's much more obvious that there's information in it
0:15:53 > 0:15:55and it's interesting as well because I tell you what -
0:15:55 > 0:15:58you'd never burn your mouth on a hot drink ever again,
0:15:58 > 0:16:02cos who would ever drink something that looks like liquid fire?
0:16:02 > 0:16:03But this is perfect.
0:16:06 > 0:16:08This unusual perspective
0:16:08 > 0:16:11demonstrates that colour carries information.
0:16:12 > 0:16:15And once you can detect invisible colour,
0:16:15 > 0:16:18you can draw a whole new picture of the world.
0:16:39 > 0:16:43I'm about to witness some of the most extraordinary new vistas
0:16:43 > 0:16:45that the infrared has opened up to us.
0:16:49 > 0:16:52This is Nasa's Flight Research Centre in Southern California.
0:16:56 > 0:17:00This Boeing 747 may not look particularly unusual,
0:17:00 > 0:17:03but it's got something very clever hidden inside.
0:17:09 > 0:17:12This plane started life as an ordinary passenger jet,
0:17:12 > 0:17:15but these days, it's something really special.
0:17:19 > 0:17:20And I'm really excited
0:17:20 > 0:17:24because I'm going to get to fly with it on its next mission.
0:17:24 > 0:17:27Like any other aircraft, it's going to take off from an airfield
0:17:27 > 0:17:30and, like any other jet, it's going to go through the weather
0:17:30 > 0:17:33to the top of the first layer of the atmosphere.
0:17:33 > 0:17:36But then it's going to keep going,
0:17:36 > 0:17:39up into the stratosphere, above almost all the water vapour.
0:17:41 > 0:17:45At that point, the back of the aircraft will open up
0:17:45 > 0:17:48and what will be revealed is a telescope
0:17:48 > 0:17:52capable of looking at the richness of the universe in the infrared,
0:17:52 > 0:17:56and I will be closer to the stars than I've ever been in my life.
0:18:01 > 0:18:07Meet SOFIA - the Stratospheric Observatory for Infrared Astronomy.
0:18:08 > 0:18:10So here we are, ready to go.
0:18:10 > 0:18:12There are 25 people on this aircraft.
0:18:12 > 0:18:14The crew and the scientists are all back there
0:18:14 > 0:18:18doing the last preparations and I'm really excited about two things -
0:18:18 > 0:18:21one is that we're going to fly around the back of the planet
0:18:21 > 0:18:25in the dark looking out at the universe.
0:18:25 > 0:18:28The other one is that I've never had this much legroom
0:18:28 > 0:18:30on a flight in my entire life.
0:18:32 > 0:18:34- OVER RADIO:- '45.
0:18:34 > 0:18:36'50, valves closed.
0:18:36 > 0:18:37'Six-ten.
0:18:37 > 0:18:39'Six-ten.
0:18:39 > 0:18:40'Ten degrees.'
0:18:44 > 0:18:46Right now, we've just left Nevada
0:18:46 > 0:18:49and we're just abeam Salt Lake City right now.
0:18:49 > 0:18:50So Salt Lake City is right over there?
0:18:50 > 0:18:52Salt Lake City is right there.
0:18:52 > 0:18:54And you do have the best view on the plane.
0:18:54 > 0:18:56It's the greatest view of the world.
0:18:56 > 0:18:57This is the best job in the world.
0:18:57 > 0:18:59That's the pilot's privilege, isn't it?
0:18:59 > 0:19:01- To look out at the sky.- It is.
0:19:01 > 0:19:02The higher we go,
0:19:02 > 0:19:07the better the telescope can "see", for lack of a better term,
0:19:07 > 0:19:09because there's less moisture in the air the higher we go.
0:19:09 > 0:19:12INDISTINCT RADIO CHATTER
0:19:16 > 0:19:17We've got the mission director,
0:19:17 > 0:19:20so this is the science heart of the mission.
0:19:20 > 0:19:23This is where the decisions are being made.
0:19:23 > 0:19:24SHE CALLS TO COLLEAGUE
0:19:26 > 0:19:30And this is the science ops, the chief scientists,
0:19:30 > 0:19:33the people who control the science ops are sitting here.
0:19:33 > 0:19:36They're looking right at the telescope.
0:19:36 > 0:19:37They've got data on the screens.
0:19:37 > 0:19:40You can see the constellations that they're following.
0:19:42 > 0:19:44It's the beginning of another long flight
0:19:44 > 0:19:49for SOFIA's Science Operations Manager Dr Jim De Buizer.
0:19:50 > 0:19:54Tell me why infrared astronomy is worth all of this effort.
0:19:54 > 0:19:56There's a lot of dust and gas between us
0:19:56 > 0:19:58and a lot of objects of interest.
0:19:58 > 0:20:00Stars when they form, for instance,
0:20:00 > 0:20:04are completely enshrouded in their natal cocoon of dust and gas.
0:20:04 > 0:20:06The infrared allows us to peer into that
0:20:06 > 0:20:08and look at what's going on
0:20:08 > 0:20:11at the centre of these star-forming regions
0:20:11 > 0:20:14and actually find out how these stars form.
0:20:14 > 0:20:18I like to use the analogy of a car radio and a GPS.
0:20:18 > 0:20:19You can go into a tunnel
0:20:19 > 0:20:21and you can't get your GPS to go any more,
0:20:21 > 0:20:22but you can get a radio signal
0:20:22 > 0:20:25and that's because a radio has a much longer wavelength.
0:20:25 > 0:20:27So when we're looking into space,
0:20:27 > 0:20:29going for longer wavelengths like the infrared
0:20:29 > 0:20:31allows us to penetrate areas
0:20:31 > 0:20:34and see things that we can't see in the optical.
0:20:34 > 0:20:36We're observing the invisible.
0:20:40 > 0:20:43Probing the hidden secrets of the universe
0:20:43 > 0:20:46by placing a 17-tonne telescope in the back of a jumbo jet
0:20:46 > 0:20:49isn't the easiest thing to do.
0:20:51 > 0:20:55Even a tiny bump could blur the image of the sky,
0:20:55 > 0:20:58making careful scientific measurements impossible.
0:21:00 > 0:21:05The telescope is just behind me on the other side of that blue wall.
0:21:05 > 0:21:09It's a big dish and it's pointing out that way into the sky.
0:21:09 > 0:21:11The thing is, when we think about telescopes like that,
0:21:11 > 0:21:13we think of them being really solid.
0:21:13 > 0:21:17They stay in one place on the ground and point at one thing in the sky.
0:21:17 > 0:21:20The problem here is it's on a moving plane that's bouncing around
0:21:20 > 0:21:23in turbulence and the way it deals with it is really clever.
0:21:25 > 0:21:30The telescope is held by motors that are actively adjusting its position
0:21:30 > 0:21:33so that it doesn't move relative to its celestial target.
0:21:34 > 0:21:38The plane bumps up and down around it, but the telescope stays still.
0:21:40 > 0:21:44So even though it looks as though we're moving quite a lot,
0:21:44 > 0:21:46SOFIA can stay locked on just one star.
0:21:48 > 0:21:53This telescope is using the long wavelengths of infrared
0:21:53 > 0:21:56to peer into the inner workings of stars,
0:21:56 > 0:22:00opening windows on the universe not available from the ground.
0:22:02 > 0:22:05You've got an image here that SOFIA has taken in the past.
0:22:05 > 0:22:08This is a picture of the Orion Nebula.
0:22:08 > 0:22:10Most of the Orion Nebula is dark
0:22:10 > 0:22:14because there is a lot of dust and gas in this nebula.
0:22:14 > 0:22:17So what's going on is there are actually a cluster
0:22:17 > 0:22:20of very massive stars at the centre of this nebula.
0:22:20 > 0:22:22What you are seeing here is not something
0:22:22 > 0:22:25that you actually can see in the visible.
0:22:25 > 0:22:27What it looks like is empty space,
0:22:27 > 0:22:31but when we look at it in infrared, it completely lights up.
0:22:31 > 0:22:35So when we look out at the night sky, we assume that when we see black,
0:22:35 > 0:22:38it's because there's nothing there, but actually that might not be true.
0:22:41 > 0:22:45This is the iconic Horsehead Nebula.
0:22:45 > 0:22:48In visible light, it appears to be a black void.
0:22:50 > 0:22:54But in the infrared, it's revealed in a whole new light.
0:22:56 > 0:23:00Delicate plumes of gas and dust billow through space.
0:23:01 > 0:23:04Far from being a beautiful curiosity,
0:23:04 > 0:23:07infrared reveals the Horsehead Nebula
0:23:07 > 0:23:12for what it really is - an active stellar nursery,
0:23:12 > 0:23:15full of the raw materials from which stars are born.
0:23:20 > 0:23:24As well as SOFIA, infrared telescopes on satellites in orbit
0:23:24 > 0:23:28around the Earth have also sent back spectacular images
0:23:28 > 0:23:32of the cosmos that would be invisible to the naked eye.
0:23:35 > 0:23:38It's all calmed down now, but it is nearly 4am.
0:23:38 > 0:23:41We've been in the air for almost eight hours
0:23:41 > 0:23:43and everyone is getting a bit tired.
0:23:43 > 0:23:46Part of the reason that this last leg is so long
0:23:46 > 0:23:48is that the star they're looking at
0:23:48 > 0:23:53is so faint that they need to take pictures of it for three hours
0:23:53 > 0:23:57just to gather enough light to get a really good image.
0:23:57 > 0:24:00The other thing about this point in the flight, though,
0:24:00 > 0:24:03is that because it's near the end, the aircraft isn't carrying much fuel
0:24:03 > 0:24:06and that means we're as high as we're going to get.
0:24:06 > 0:24:10We're at 43,000 feet, which is just over 13km.
0:24:10 > 0:24:13It's the highest up I've ever been in my life.
0:24:13 > 0:24:16But we are now on the way home.
0:24:19 > 0:24:22Seeing these scientists observe distant stars
0:24:22 > 0:24:27during a bumpy night flight in a 747 has been really impressive.
0:24:33 > 0:24:35Looking out from the stratosphere
0:24:35 > 0:24:40allows SOFIA to capture infrared wavelengths that would never make it
0:24:40 > 0:24:42through Earth's atmosphere to the ground,
0:24:42 > 0:24:45giving us a whole new perspective on the universe.
0:24:50 > 0:24:53It's been a huge privilege to fly on SOFIA.
0:24:53 > 0:24:57As we were going, I started to think of her as a flying eye
0:24:57 > 0:25:00looking out into the cosmos for all of us.
0:25:01 > 0:25:05And I think the real message to take away
0:25:05 > 0:25:09is that the dark regions of the night sky may not be dark
0:25:09 > 0:25:12if you can look in all the colours that there are.
0:25:12 > 0:25:13Because it's not just the infrared -
0:25:13 > 0:25:18the palette of the universe has a huge range of colours in it.
0:25:18 > 0:25:22And now, as we look out into the universe,
0:25:22 > 0:25:26we're starting to paint our picture of it with the full range of colours
0:25:26 > 0:25:27that nature has on offer.
0:25:31 > 0:25:34Venture further out beyond the infrared
0:25:34 > 0:25:36and there are even longer wavelengths.
0:25:38 > 0:25:40Microwaves and radio waves.
0:25:42 > 0:25:44Invisible light that has given us
0:25:44 > 0:25:47our deepest insights into the universe.
0:25:47 > 0:25:50Faint signals from the dawn of time itself.
0:25:52 > 0:25:55We've harnessed these wavelengths closer to home too,
0:25:55 > 0:26:00transforming how we communicate and how we live our lives.
0:26:01 > 0:26:03But the story doesn't end there.
0:26:07 > 0:26:10After Herschel's discovery of infrared,
0:26:10 > 0:26:14the hunt was now on to find even more exotic and bizarre colours.
0:26:16 > 0:26:20The obvious place to look was at the other end of the spectrum.
0:26:28 > 0:26:30In 1800,
0:26:30 > 0:26:33just a year after the discovery of infrared,
0:26:33 > 0:26:35German physicist Johann Ritter
0:26:35 > 0:26:38found a colour beyond the blue part of the spectrum.
0:26:42 > 0:26:45Though we can't see it, we've certainly heard of it.
0:26:45 > 0:26:48It's all around us, especially in summer.
0:26:52 > 0:26:56That colour is ultraviolet, or UV.
0:26:57 > 0:27:01UV has a short wavelength and lots of energy,
0:27:01 > 0:27:03which makes it both good and bad for us.
0:27:06 > 0:27:09It helps our body produce Vitamin D,
0:27:09 > 0:27:12but too much of it can damage our cells and lead to skin cancer.
0:27:14 > 0:27:19It's a colour that matters, even if we humans can't see it.
0:27:23 > 0:27:25But there are other animals that can.
0:27:29 > 0:27:33To begin to explore the hidden world of ultraviolet,
0:27:33 > 0:27:34I'm meeting Ron Douglas,
0:27:34 > 0:27:38professor of visual neuroscience at London City University.
0:27:41 > 0:27:44And some very friendly birds.
0:27:44 > 0:27:45We've got starlings here,
0:27:45 > 0:27:48who are eagerly pecking away at the food we have got for them.
0:27:50 > 0:27:53Starlings have a special relationship with UV.
0:27:53 > 0:27:56Their eyes can see this colour
0:27:56 > 0:27:59and some of the female birds' feathers reflect it.
0:28:00 > 0:28:01I'm intrigued to know why.
0:28:03 > 0:28:06They are actually very, very sensitive to UV.
0:28:06 > 0:28:09They have photoreceptors that respond in the UV
0:28:09 > 0:28:11and they also have lenses at the front of the eye
0:28:11 > 0:28:13that let the UV through,
0:28:13 > 0:28:16so they really are true experts at UV vision.
0:28:16 > 0:28:21And what is it they are looking at, what can they see with UV vision?
0:28:21 > 0:28:22SHE LAUGHS
0:28:22 > 0:28:25When it comes down to it, for most animals,
0:28:25 > 0:28:27life is really about two things -
0:28:27 > 0:28:29it's about food and sex.
0:28:29 > 0:28:32Perhaps UV-reflecting female starlings
0:28:32 > 0:28:35are attractive to male starlings,
0:28:35 > 0:28:40cos female UV-reflecting starlings, they have much bigger brood sizes,
0:28:40 > 0:28:42they are more effective at having young,
0:28:42 > 0:28:45so that must mean they are more effective
0:28:45 > 0:28:47at attracting the male starling.
0:28:47 > 0:28:50We've got a mixed group around us, both males and females.
0:28:50 > 0:28:53I can't tell the difference between them just by looking at them.
0:28:53 > 0:28:56Some of the bits of their feathers reflect ultraviolet light.
0:28:56 > 0:28:59Of course, we're completely unaware of that.
0:28:59 > 0:29:03But they are attracted, in part, to the ultraviolet colours.
0:29:03 > 0:29:05So there is no excuse at all for thinking that the world
0:29:05 > 0:29:09is the way we humans see it and that we have the best vision of all.
0:29:09 > 0:29:10No, absolutely.
0:29:10 > 0:29:14In most respects, we have inferior vision to a lot of animals,
0:29:14 > 0:29:17so we've seen that we don't see ultraviolet light,
0:29:17 > 0:29:19but a lot of animals do.
0:29:19 > 0:29:21In fact, for every aspect of vision,
0:29:21 > 0:29:24you can pick out an animal and it does it better than us.
0:29:29 > 0:29:32One creature that's long had a reputation
0:29:32 > 0:29:35for superb eyesight is the eagle.
0:29:37 > 0:29:38Meet Sasha.
0:29:42 > 0:29:44Well, we've got a... EAGLE SCREECHES
0:29:44 > 0:29:47..quite a noisy eagle here. He's talking away to us.
0:29:47 > 0:29:49And he's having a good look at everything,
0:29:49 > 0:29:52but he's not seeing the world in quite the same way that we are.
0:29:52 > 0:29:54What's different about his vision?
0:29:54 > 0:29:58His ability to see detail is about twice as good as ours.
0:29:58 > 0:30:00It's like having more pixels in your camera.
0:30:00 > 0:30:03The more pixels, the higher the quality of the image.
0:30:05 > 0:30:09Until recently, it was generally thought that all birds of prey
0:30:09 > 0:30:12had UV vision and that this made them better hunters.
0:30:14 > 0:30:18There was a very nice story going around that raptors in general
0:30:18 > 0:30:23could follow the urine trails laid down by small mammals.
0:30:23 > 0:30:26Since urine reflects ultraviolet light,
0:30:26 > 0:30:29it was thought that raptors could probably find voles
0:30:29 > 0:30:32by following the UV reflecting from urine trails.
0:30:35 > 0:30:37Sadly, that seems not to be true
0:30:37 > 0:30:41and it's not really true that he doesn't have the photo receptors
0:30:41 > 0:30:46to see ultraviolet light, but he actually puts a filter in his lens
0:30:46 > 0:30:48that cuts out most of the ultraviolet light.
0:30:51 > 0:30:54On the face of it, ultraviolet sounds as though it should be
0:30:54 > 0:30:56extremely useful to a top predator...
0:30:58 > 0:31:01..but there's a reason Sasha doesn't make use of it.
0:31:02 > 0:31:05The one thing we do know about birds of prey
0:31:05 > 0:31:07is that they have amazingly keen eyesight.
0:31:07 > 0:31:10They are really good at seeing fine detail.
0:31:10 > 0:31:12Now, a problem with ultraviolet light
0:31:12 > 0:31:15is it's scattered more than other wavelengths,
0:31:15 > 0:31:18so ultraviolet light gives you poor images.
0:31:20 > 0:31:25As a bird of prey, the last thing you want when hunting small animals
0:31:25 > 0:31:28is a lot of scattered light and a blurry image.
0:31:30 > 0:31:33And that's why Sasha has a lens over his eye
0:31:33 > 0:31:36that filters out the unhelpful ultraviolet.
0:31:38 > 0:31:42We humans have also evolved to filter out UV,
0:31:42 > 0:31:45both for visual acuity and protection.
0:31:48 > 0:31:51But there are other animals which are not privileged
0:31:51 > 0:31:53with very sharp vision.
0:31:55 > 0:31:56Take the honeybee.
0:31:59 > 0:32:02It doesn't see a clear view of the world at all,
0:32:02 > 0:32:06but it can see ultraviolet and that gives it a huge advantage.
0:32:08 > 0:32:11How is it determined which animals can use which colours?
0:32:11 > 0:32:14Well, really, you have to look at it rather differently and think,
0:32:14 > 0:32:17"What does the animal actually use its eyes for?"
0:32:17 > 0:32:20What is the difference between what a bee has to see
0:32:20 > 0:32:23and what a bird of prey has to see and what a songbird has to see?
0:32:24 > 0:32:27The bee needs to find the flower with the nectar.
0:32:28 > 0:32:33The flower needs to attract the bee to pollinate it.
0:32:33 > 0:32:36To discover how they use UV to do it,
0:32:36 > 0:32:38I need to see the world the way the bees do.
0:32:40 > 0:32:41So how is this camera going to help us?
0:32:41 > 0:32:43This camera will show us
0:32:43 > 0:32:47the parts of the spectrum that the bee can see, but we can't see,
0:32:47 > 0:32:51so it'll show us the bees' hidden world, if you like.
0:32:51 > 0:32:55This is the ultraviolet world that the bee has access to.
0:32:57 > 0:33:01At every turn there are hidden signs and codes.
0:33:01 > 0:33:03What I can see is that these flowers
0:33:03 > 0:33:05have really dramatic patterns on them.
0:33:05 > 0:33:07That just looks yellow here.
0:33:07 > 0:33:09Absolutely, but it's rather confusing.
0:33:09 > 0:33:14If you can't see, or if you just saw plain yellow,
0:33:14 > 0:33:17you would actually be hard-pushed to know where the nectar was.
0:33:17 > 0:33:19It would be really useful to have a signal,
0:33:19 > 0:33:22like guiding lights, to show you where the nectar is.
0:33:22 > 0:33:25Kind of like arrows, saying, "Nectar here".
0:33:27 > 0:33:30Seen in ultraviolet, some flowers do exactly that.
0:33:32 > 0:33:36To the bees, these UV signals are like advertising hoardings
0:33:36 > 0:33:39highlighting where the nectar and pollen are.
0:33:41 > 0:33:45These markings are caused by pigments in the flower called flavonoids,
0:33:45 > 0:33:49some of which are visible in the ultraviolet.
0:33:49 > 0:33:51It's a world of patterns
0:33:51 > 0:33:54and shapes that's completely hidden from our eyes.
0:33:57 > 0:33:59The bee gets by without much detail.
0:34:01 > 0:34:04Being able to see UV allows it to find the right flowers
0:34:04 > 0:34:07and get back to the hive with its precious cargo
0:34:07 > 0:34:09as quickly as possible.
0:34:09 > 0:34:12And so this is all about survival?
0:34:12 > 0:34:15It is. You have eyes that serve your needs, basically.
0:34:16 > 0:34:20We're still only just beginning to appreciate the hidden world
0:34:20 > 0:34:23of the ultraviolet and its vital role in nature.
0:34:26 > 0:34:29Yet even this isn't the end of the spectrum of colours
0:34:29 > 0:34:30that come from the sun.
0:34:44 > 0:34:49Beyond ultraviolet is a final swathe of hidden colours
0:34:49 > 0:34:52that perhaps have the greatest potential to shape our future.
0:34:53 > 0:34:55We can't see inside our own bodies
0:34:55 > 0:34:58and, on a daily basis, most of us really wouldn't want to.
0:35:00 > 0:35:03But just imagine, back in 1895,
0:35:03 > 0:35:05seeing this for the first time.
0:35:07 > 0:35:10It's the first ever X-ray, it was taken by Wilhelm Rontgen,
0:35:10 > 0:35:12and the picture is of his wife's hand.
0:35:12 > 0:35:16You can see the bones in her fingers and her wedding ring here.
0:35:16 > 0:35:18This was a shocking image because,
0:35:18 > 0:35:21up till then, skeletons were only ever seen after you were dead.
0:35:21 > 0:35:24Rontgen's wife was well aware of that. She was horrified.
0:35:24 > 0:35:26She said, "I have seen my own death."
0:35:28 > 0:35:31Rontgen called these mysterious rays "X-rays"
0:35:31 > 0:35:34because he didn't know what they were and the name has stuck.
0:35:37 > 0:35:40We now know they're a type of invisible light,
0:35:40 > 0:35:42an invisible rainbow of colours,
0:35:42 > 0:35:45with a very short wavelength and a very high energy.
0:35:47 > 0:35:49High enough to pass through tissue
0:35:49 > 0:35:52and reveal the hidden world inside the human body.
0:35:54 > 0:35:57But this new colour came at a price.
0:35:59 > 0:36:01The early X-ray pioneers were known as roentgenologists
0:36:01 > 0:36:03and there was a meeting of them in 1920,
0:36:03 > 0:36:06where they met from all over Europe.
0:36:06 > 0:36:08They sat down to dinner, a chicken dinner,
0:36:08 > 0:36:11but almost none of them would be able to eat the meal
0:36:11 > 0:36:15because almost none of them would be able to cut the meat,
0:36:15 > 0:36:19because they were missing fingers and hands from radiation damage.
0:36:23 > 0:36:27Today, we understand much better the dangers posed by radiation.
0:36:29 > 0:36:31Doctors still rely on Roentgen's X-rays
0:36:31 > 0:36:34as a powerful diagnostic tool.
0:36:35 > 0:36:39Thanks to new technologies, we can even use them to create
0:36:39 > 0:36:43detailed images of our bones and joints while they're moving.
0:36:47 > 0:36:49It's a bit like an X-ray movie,
0:36:49 > 0:36:53allowing surgeons to see what's really going on inside us.
0:36:56 > 0:37:00This invisible colour can reveal the hidden world of the human body
0:37:00 > 0:37:03at the scale of bones and joints.
0:37:03 > 0:37:06But if you want to see something smaller,
0:37:06 > 0:37:10to probe the very structure of matter itself, you soon hit a problem.
0:37:13 > 0:37:16The visible light all around me has a tiny wavelength,
0:37:16 > 0:37:19the distance between two peaks of the wave
0:37:19 > 0:37:22is less than a thousandth of a millimetre.
0:37:22 > 0:37:25That is fine for seeing things that are bigger than that wavelength,
0:37:25 > 0:37:28but anything smaller is a problem
0:37:28 > 0:37:32and atoms are a thousand times smaller again.
0:37:32 > 0:37:34There is a way around this problem,
0:37:34 > 0:37:37but as is often the way with physics,
0:37:37 > 0:37:39the smaller the thing you're looking at,
0:37:39 > 0:37:42the bigger your piece of kit needs to be.
0:37:46 > 0:37:49And they don't come much bigger than this.
0:37:52 > 0:37:55It may look like a giant spaceship that's landed
0:37:55 > 0:37:59in the Oxfordshire countryside, but it's actually a synchrotron.
0:37:59 > 0:38:05It's a huge circular machine capable of generating light
0:38:05 > 0:38:07that's ten billion times brighter than the sun...
0:38:08 > 0:38:11..including high-energy X-rays
0:38:11 > 0:38:16that can reveal the hidden wonders of the world at the microscopic scale.
0:38:18 > 0:38:21I won't ever directly see the molecules that are keeping me alive
0:38:21 > 0:38:23because the colours I can see
0:38:23 > 0:38:27and the way that I see just can't touch that level of detail.
0:38:28 > 0:38:32But here they can watch a single colour
0:38:32 > 0:38:36ripple through a giant molecule and look at the patterns you get
0:38:36 > 0:38:38when light interacts with matter,
0:38:38 > 0:38:42and they're so sophisticated at that that they can visualise
0:38:42 > 0:38:46on an atomic scale the architecture of life.
0:38:50 > 0:38:55The Diamond Light Source synchrotron works like a giant microscope,
0:38:55 > 0:39:00producing invisible wavelengths of light of extremely high energy.
0:39:00 > 0:39:02So would you come down here very often?
0:39:02 > 0:39:05Generally, generally, we don't....
0:39:05 > 0:39:08'This invisible light is used by scientists like Dr Anna Warren
0:39:08 > 0:39:10'to probe a world so tiny
0:39:10 > 0:39:14'that it was beyond our reach until very recently.'
0:39:16 > 0:39:18So this is called the storage ring
0:39:18 > 0:39:21and what's happening in here is the electrons are spinning round
0:39:21 > 0:39:24the circumference, which is about 562 metres.
0:39:24 > 0:39:26The electrons are going almost the speed of light
0:39:26 > 0:39:29so they're going really, really fast.
0:39:30 > 0:39:33As the electrons race around the storage ring,
0:39:33 > 0:39:36powerful magnets alter their direction,
0:39:36 > 0:39:41causing the electrons to release energy in the form of X-rays.
0:39:42 > 0:39:44The only reason we can stand here now
0:39:44 > 0:39:46- is because this isn't switched on, right?- Yep.
0:39:46 > 0:39:48We definitely wouldn't want to be in here
0:39:48 > 0:39:50when the electron beam was running round.
0:39:50 > 0:39:53The synchrotron can produce invisible colours
0:39:53 > 0:39:57of such high energy and such short wavelengths
0:39:57 > 0:39:59that they can penetrate the molecules
0:39:59 > 0:40:01that make up the world around us
0:40:01 > 0:40:04and reveal their shape and structure.
0:40:06 > 0:40:09It's a technique that has its roots in the 1950s,
0:40:09 > 0:40:14when Rosalind Franklin famously used X-rays to unlock the shape
0:40:14 > 0:40:18of the most celebrated molecule in the history of science -
0:40:18 > 0:40:21the double-helix structure of DNA.
0:40:25 > 0:40:29Today, the focus of this type of research is proteins,
0:40:29 > 0:40:33the most crucial cogs in the molecular machinery of life.
0:40:34 > 0:40:37They carry out nearly all the vital processes
0:40:37 > 0:40:39that keep living organisms ticking along.
0:40:39 > 0:40:43For every protein, shape is key to its function.
0:40:45 > 0:40:48It's only when we can see the details of a protein's shape
0:40:48 > 0:40:51that we can really understand how it works.
0:40:52 > 0:40:57So we've got an example up here of a protein, so...
0:40:57 > 0:41:00- That looks like tangled knitting. - Yes.
0:41:00 > 0:41:03But you can see that it's a very complex structure,
0:41:03 > 0:41:06but we might be able to understand certain pockets within here,
0:41:06 > 0:41:07like this dip here.
0:41:07 > 0:41:09Knowing the shape, we might be able to say,
0:41:09 > 0:41:12"Oh, look, there's an area here or an area here
0:41:12 > 0:41:15"that may interact with something in our body."
0:41:17 > 0:41:21It was in 1965 that scientists, using X-rays,
0:41:21 > 0:41:26first deduced the shape of a specific type of protein called an enzyme.
0:41:27 > 0:41:29It came from the humble egg.
0:41:31 > 0:41:34Known as lysozyme, it's an antibacterial enzyme
0:41:34 > 0:41:38which keeps eggs bug-free, even when you don't keep them in the fridge.
0:41:41 > 0:41:45But you can't just X-ray an egg to reveal the shape of lysozyme.
0:41:47 > 0:41:51You first need to grow lysozyme molecules into a crystal.
0:41:53 > 0:41:55A crystal is not something I associate with an egg.
0:41:55 > 0:41:59No. So the crystal is really key to the experiment.
0:41:59 > 0:42:02So we're forcing the protein molecules
0:42:02 > 0:42:04to pack in a very regular manner,
0:42:04 > 0:42:08so we'll have protein molecules extending in three dimensions.
0:42:08 > 0:42:10It has to be very regular
0:42:10 > 0:42:12and it forms these layers within the crystal.
0:42:12 > 0:42:15It's these layers that then interact with the X-rays
0:42:15 > 0:42:18and allow us to get information about the structure.
0:42:21 > 0:42:24What's so crucial about crystals is that the molecules within them
0:42:24 > 0:42:28are arranged in a highly regular, repeating pattern.
0:42:29 > 0:42:32And it's only when the molecules are in this form
0:42:32 > 0:42:35that the invisible X-rays can reveal their secrets.
0:42:37 > 0:42:40The technique is known as X-ray crystallography
0:42:40 > 0:42:44and it's the same principle that Rosalind Franklin used.
0:42:44 > 0:42:48The way you get from the structure of a crystal to a pattern
0:42:48 > 0:42:52is really clever, it's a nice little bit of physics called diffraction.
0:42:52 > 0:42:56On the end of the ruler here, there are lots of black lines
0:42:56 > 0:42:58and, on this side, they're inches,
0:42:58 > 0:43:03so they're divided up into tenths of an inch,
0:43:03 > 0:43:06and I've got a laser pointer here which is shining at those
0:43:06 > 0:43:10and it's reflecting off each of the gaps in-between the markers.
0:43:10 > 0:43:13So this is like X-ray light coming in and reflecting off
0:43:13 > 0:43:17each of the crystal layers, each of those plains within the crystal.
0:43:17 > 0:43:20And if I switch on my laser pointer,
0:43:20 > 0:43:22what I can see on the wall over there is a pattern of dots
0:43:22 > 0:43:25and they're very evenly spaced.
0:43:25 > 0:43:27There's a strange thing about this -
0:43:27 > 0:43:31you can see that the dots are quite close together.
0:43:32 > 0:43:37And the lines on the inches side here are quite far apart.
0:43:37 > 0:43:39If I move the ruler across to the other side...
0:43:41 > 0:43:43..the millimetre marks are much, much closer together
0:43:43 > 0:43:46and the dots on the wall have got further apart.
0:43:46 > 0:43:50So the weird thing about diffraction is the way that these waves work
0:43:50 > 0:43:53is that the closer together your plains are,
0:43:53 > 0:43:55the further apart the spots are.
0:43:56 > 0:44:00Today, despite having a synchrotron at her disposal,
0:44:00 > 0:44:04Anna still has to turn any molecule into a crystal
0:44:04 > 0:44:05before she can work out its shape.
0:44:09 > 0:44:13First, she chooses the best crystal.
0:44:13 > 0:44:15It takes a steady hand to retrieve it.
0:44:21 > 0:44:23A robot arm picks up the crystal
0:44:23 > 0:44:25and places it in front of the X-ray beam.
0:44:28 > 0:44:30To work out the shape of the molecule,
0:44:30 > 0:44:34we look in more detail at what we call the intensity of the spot,
0:44:34 > 0:44:39so we're looking at whether this spot is brighter than this spot.
0:44:39 > 0:44:42Very quickly, we can obtain information about the size
0:44:42 > 0:44:46of the molecules from looking at the spacing between these spots.
0:44:48 > 0:44:52By analysing the exact position and intensity of these spots,
0:44:52 > 0:44:56Anna can work out the location of every atom.
0:44:56 > 0:45:00This allows her to construct a three-dimensional image
0:45:00 > 0:45:03of some of the most complicated structures in nature.
0:45:03 > 0:45:08So this is the structure that we've obtained from the lysozyme crystals.
0:45:08 > 0:45:11So you can see it is quite a complex molecule
0:45:11 > 0:45:14and you can see all the atoms packing together
0:45:14 > 0:45:16into this three-dimensional shape.
0:45:16 > 0:45:22We can rotate the molecule round and you can get an idea about
0:45:22 > 0:45:24the full three-dimensional shape of it.
0:45:27 > 0:45:31The mystery of lysozyme's structure can only be solved
0:45:31 > 0:45:34with the help of invisible colours like X-rays.
0:45:36 > 0:45:40They help us resolve not just the fine details of the molecule's shape,
0:45:40 > 0:45:42but also how they work.
0:45:43 > 0:45:48This cleft area is where the lysozyme grabs hold of bacteria.
0:45:50 > 0:45:54X-ray diffraction shows that once it has grabbed the bacteria,
0:45:54 > 0:45:56the cleft subtly changes shape,
0:45:56 > 0:46:01breaking the bacterial cell wall and ultimately killing it.
0:46:03 > 0:46:07That isn't just crucially important for keeping eggs fresh.
0:46:07 > 0:46:11Lysozyme is also a vital component of our immune system.
0:46:13 > 0:46:15I mean, it's a very exciting process,
0:46:15 > 0:46:17when you've spent years trying to crystallise it
0:46:17 > 0:46:19and then you can see your structure on the screen.
0:46:19 > 0:46:21People don't mind spending years doing it,
0:46:21 > 0:46:23because once you get that information,
0:46:23 > 0:46:25there's so much you can do with it.
0:46:25 > 0:46:27It can help numerous groups
0:46:27 > 0:46:30to help develop medicine and vaccines and things.
0:46:32 > 0:46:34The sheer size of the synchrotron
0:46:34 > 0:46:37means it can produce a vast range of intensities
0:46:37 > 0:46:39and wavelengths of light.
0:46:40 > 0:46:43The shorter the wavelength, the higher the energy
0:46:43 > 0:46:46and the smaller the world you can probe.
0:46:48 > 0:46:49It's enabled the synchrotron
0:46:49 > 0:46:52to penetrate the hidden structures of matter,
0:46:52 > 0:46:55allowing us to achieve medical breakthroughs,
0:46:55 > 0:47:00build ever-shrinking machines and design new wonder materials.
0:47:02 > 0:47:05The knowledge that flows from this technology
0:47:05 > 0:47:08is allowing us to understand the world as never before,
0:47:08 > 0:47:11pushing back the boundaries of science.
0:47:13 > 0:47:17The entire spectrum of colours is vast and fascinating.
0:47:17 > 0:47:20It allows us to see everything from the building blocks of life
0:47:20 > 0:47:23to the furthest stars and galaxies.
0:47:26 > 0:47:29It's this ability to harness the invisible
0:47:29 > 0:47:32that's allowed us to see so much more of the world
0:47:32 > 0:47:33than our own eyes can perceive.
0:47:35 > 0:47:40And now, scientists are starting to use the properties of colour
0:47:40 > 0:47:44to do something that will have perhaps the most profound impact
0:47:44 > 0:47:45on our lives in the future...
0:47:52 > 0:47:55..to see inside the human body
0:47:55 > 0:47:58in a way that's never been possible before.
0:48:02 > 0:48:05Professor Mark Lythgoe from University College London
0:48:05 > 0:48:08is at the cutting edge of this new frontier of colour.
0:48:10 > 0:48:14This is the exciting new world of biomedical imaging.
0:48:16 > 0:48:19The body is a real challenge. It's a complete black box.
0:48:19 > 0:48:21There is no light in there
0:48:21 > 0:48:25and somehow we've got to make the body light up.
0:48:26 > 0:48:29Mark's way of doing this sounds a little bit like science fiction.
0:48:32 > 0:48:35He calls it the Invisible Man Project.
0:48:36 > 0:48:40Over here is a sample from a heart.
0:48:40 > 0:48:42Hold that.
0:48:42 > 0:48:45I think most people know that tissue inside our bodies
0:48:45 > 0:48:48is a pink-y, pale pink-y colour apart from things like the liver,
0:48:48 > 0:48:50which are really darkly brown.
0:48:50 > 0:48:54- This is the magic behind it.- OK.
0:48:54 > 0:48:55If I can get you to hold this.
0:48:57 > 0:48:58- It's a bit slippery.- Yeah, got it.
0:48:58 > 0:49:05And the idea is we make it completely disappear
0:49:05 > 0:49:06from the bottom up, I hope.
0:49:06 > 0:49:08- SHE LAUGHS - OK.
0:49:08 > 0:49:09Let's see if we can see this.
0:49:10 > 0:49:14Mark places a hollow glass tube inside a container of liquid.
0:49:16 > 0:49:18- And then watch the bottom.... - Oh, I love this! It's vanishing,
0:49:18 > 0:49:20it's vanishing! That's brilliant!
0:49:20 > 0:49:22It's brilliant, I love this!
0:49:23 > 0:49:26So it's like the tube is just disappearing,
0:49:26 > 0:49:28- but the blue stripe's still there. - Yeah.
0:49:29 > 0:49:33So the liquid is filling the tube from the inside
0:49:33 > 0:49:36- and wherever it's full, it's just vanished.- Yeah.
0:49:37 > 0:49:41This vanishing trick illustrates an important property of light.
0:49:43 > 0:49:46When light passes through a material such as glass,
0:49:46 > 0:49:48it slows down and gets bent,
0:49:48 > 0:49:52and its path depends on a property called its refractive index.
0:49:53 > 0:49:55It's what allows us to see the glass.
0:49:57 > 0:49:59If the refractive index of two materials,
0:49:59 > 0:50:03like the liquid and the glass, is the same,
0:50:03 > 0:50:06light isn't bent at the point where they meet.
0:50:06 > 0:50:09Its path is undisturbed as it passes through...
0:50:10 > 0:50:14..so we have no way of seeing the glass tube.
0:50:14 > 0:50:15That's what we try to do.
0:50:15 > 0:50:19We try to match the refractive indexes in tissue
0:50:19 > 0:50:23and then, by definition, it should become transparent.
0:50:24 > 0:50:28Mark has applied this technique to reveal the hidden colours
0:50:28 > 0:50:30of a whole range of human organs.
0:50:31 > 0:50:33Certain parts of the body
0:50:33 > 0:50:36actually have the potential to give out light.
0:50:36 > 0:50:40Your brain, your heart, your liver all fluoresces naturally.
0:50:40 > 0:50:43It's called autofluorescence, but, of course, we can't see that light
0:50:43 > 0:50:44cos it doesn't get out of the body.
0:50:44 > 0:50:46So I'm lit up like a Christmas tree on the inside?
0:50:46 > 0:50:48If we could make you completely transparent,
0:50:48 > 0:50:51there will be different colours coming out of you.
0:50:51 > 0:50:52You'd be fluorescing.
0:50:52 > 0:50:54The question is, can we use that information?
0:50:55 > 0:50:58By making tissue transparent,
0:50:58 > 0:51:02Mark has found a way to use this in-built ability to fluoresce
0:51:02 > 0:51:05to do something extraordinary.
0:51:05 > 0:51:08This is a piece of liver.
0:51:08 > 0:51:14Naturally, the liver fluoresces a sort of bluey-violet colour.
0:51:14 > 0:51:16I had no idea, that's brilliant.
0:51:16 > 0:51:19The wonderful thing seems to be,
0:51:19 > 0:51:23as the tissue changes from normal tissue to diseased tissue,
0:51:23 > 0:51:26and, in this case, these are tiny cancers
0:51:26 > 0:51:29that are scattered throughout the liver.
0:51:29 > 0:51:31And for some reason, and we're not too sure of this yet,
0:51:31 > 0:51:34they give out a different colour light,
0:51:34 > 0:51:38so we can discriminate normal tissue from diseased tissue
0:51:38 > 0:51:42just by looking at the natural colours that the body gives out.
0:51:42 > 0:51:45The blue colour is the normal, healthy liver
0:51:45 > 0:51:50and anything that's gold shows the cancerous cells of a tumour.
0:51:50 > 0:51:52- So the body is doing the work for you here?- Completely.
0:51:52 > 0:51:53You don't have to add anything?
0:51:53 > 0:51:55That's right, all you need to do is tap into it.
0:51:55 > 0:51:59The trick is you have to make the body invisible.
0:51:59 > 0:52:02Mark's technique uses light and colour
0:52:02 > 0:52:04to highlight the cancerous cells.
0:52:06 > 0:52:08So far, it only works on dead tissue.
0:52:10 > 0:52:14So the next challenge is to see inside the body
0:52:14 > 0:52:16while it's still alive.
0:52:16 > 0:52:17To achieve this,
0:52:17 > 0:52:22Mark is developing a radical new technique that could allow us to see
0:52:22 > 0:52:26the colour of living body tissues while they're still inside us.
0:52:28 > 0:52:33There is a wonderful effect called the photoacoustic effect
0:52:33 > 0:52:35and, to some degree, its...
0:52:35 > 0:52:38"Remarkable" would perhaps be an understatement for it.
0:52:38 > 0:52:41You can shine light into the body
0:52:41 > 0:52:44and that light is then converted into sound.
0:52:44 > 0:52:46We measure the sound, or listen to the sound as it comes out
0:52:46 > 0:52:49of the body, and that tells us about how the body is working.
0:52:51 > 0:52:53To see this process in action,
0:52:53 > 0:52:56I have to place my hand in the path of a rather powerful laser.
0:52:58 > 0:53:00So this is all about pigments.
0:53:00 > 0:53:01Think about pigments in the body,
0:53:01 > 0:53:06but it's a different way of thinking about coloured pigments.
0:53:06 > 0:53:09Pigments have more to offer than their colour.
0:53:09 > 0:53:13Haemoglobin is one of our body's most important pigments,
0:53:13 > 0:53:16and it's responsible for picking up oxygen molecules
0:53:16 > 0:53:18and carrying them round our body.
0:53:18 > 0:53:22But it's the rich red colour of oxygenated haemoglobin
0:53:22 > 0:53:26that's crucial to Mark's cutting-edge imaging techniques.
0:53:27 > 0:53:31So the red laser goes in and it's absorbed by certain pigments
0:53:31 > 0:53:35and inside the blood vessels there are blood cells,
0:53:35 > 0:53:37and inside that there are pigments.
0:53:37 > 0:53:38They wonderfully absorb red light
0:53:38 > 0:53:42and, as they do, they just heat up a tiny bit.
0:53:42 > 0:53:46As they do, they give out a tiny sound wave.
0:53:46 > 0:53:49The light comes in, the sound comes out,
0:53:49 > 0:53:52so we create a three-dimensional map of the blood vessels
0:53:52 > 0:53:57by listening to the sound as it comes out of the red blood cells.
0:53:57 > 0:54:02The haemoglobin in my body tissues absorbs specific colours of light
0:54:02 > 0:54:06and, even though it only heats up by a minuscule amount,
0:54:06 > 0:54:10it expands quickly enough to send out detectable sound.
0:54:10 > 0:54:14The surrounding tissue doesn't absorb the colours to the same degree
0:54:14 > 0:54:17and so returns a far weaker sound signature.
0:54:17 > 0:54:22By using sound to measure these tiny differences in colour absorption,
0:54:22 > 0:54:28Mark can create a 3D image of the blood vessels inside my hand.
0:54:28 > 0:54:30Right on the surface are these tiny lines
0:54:30 > 0:54:33that you can see running through there,
0:54:33 > 0:54:36just there as they come round, like a grid pattern.
0:54:36 > 0:54:40Those are the fingerprints that are on the surface of the skin
0:54:40 > 0:54:43and, within them, they contain pigments.
0:54:43 > 0:54:45Melanin. So when you have a mole on your hand
0:54:45 > 0:54:48and it goes slightly brown, that's a pigment.
0:54:48 > 0:54:49That brown pigment.
0:54:49 > 0:54:52There are tiny differences in the pigments in your skin
0:54:52 > 0:54:55and that's also absorbing that red light
0:54:55 > 0:54:59and then expanding and giving out that tiny sound wave.
0:54:59 > 0:55:02Without adding or doing anything to you,
0:55:02 > 0:55:04we get an instant three-dimensional picture
0:55:04 > 0:55:06of the blood vessels in your hand,
0:55:06 > 0:55:08and this hasn't been done before.
0:55:08 > 0:55:11So, by using sound, you can see the colours inside our bodies
0:55:11 > 0:55:12that our eyes can't?
0:55:12 > 0:55:14Completely.
0:55:14 > 0:55:17By shining coloured light into tissue,
0:55:17 > 0:55:20and then converting that light into sound,
0:55:20 > 0:55:24the inside of my hand is revealed in exquisite detail.
0:55:24 > 0:55:27The thing that strikes me about this is that you've found a way
0:55:27 > 0:55:31to light up different systems of the body in different colours,
0:55:31 > 0:55:35so blood can be one colour and the tumour cells can be different colour,
0:55:35 > 0:55:38so you can separate out all those things in different colours
0:55:38 > 0:55:41- and see the body in a completely different way.- Yes.
0:55:41 > 0:55:43It's about the pigments, it's about the colours.
0:55:43 > 0:55:45Once you understand colours, then you can understand
0:55:45 > 0:55:48whether they're going to absorb light or reflect it.
0:55:48 > 0:55:50So where is this going in the future?
0:55:50 > 0:55:52As we've seen today, we've taken your hand
0:55:52 > 0:55:54and we've put it into the system.
0:55:54 > 0:55:57We can image people - that's a huge step forward.
0:55:57 > 0:56:00We've developed a completely new technology,
0:56:00 > 0:56:02that's out there now in several labs,
0:56:02 > 0:56:05and we're starting to use it on people.
0:56:05 > 0:56:07The next stage is to get it into hospitals.
0:56:15 > 0:56:18There's more than one way of looking at a human.
0:56:18 > 0:56:21Mark Lythgoe and his team are pioneering the ways
0:56:21 > 0:56:23that we will see ourselves in the future
0:56:23 > 0:56:26and with that will come new medical insights
0:56:26 > 0:56:30and new ways of detecting and treating disease.
0:56:30 > 0:56:34The human body is possibly the thing that's most familiar to us
0:56:34 > 0:56:37and it's shared by all the humans in history.
0:56:37 > 0:56:39Plato and Shakespeare and Queen Victoria
0:56:39 > 0:56:43all had a body with the same basic physiology
0:56:43 > 0:56:47and these new imaging techniques are letting us see that body now
0:56:47 > 0:56:48in a whole new light.
0:56:53 > 0:56:54This series has taken me
0:56:54 > 0:56:58on a journey through the story of our world in 15 colours.
0:57:00 > 0:57:02I've explored where colour comes from,
0:57:02 > 0:57:06why our planet is the most colourful place we know of,
0:57:06 > 0:57:09how colour has shaped the living world,
0:57:09 > 0:57:11and how it will mould our future.
0:57:13 > 0:57:15I had a paint box when I was a child,
0:57:15 > 0:57:21all the colours laid out on the grid, and they were so easily accessible.
0:57:21 > 0:57:25All I needed to paint the world was a paintbrush and some water.
0:57:26 > 0:57:30And now, when I look at a paint box like that, I see so much more.
0:57:32 > 0:57:35In red, there's the history of the early earth.
0:57:37 > 0:57:40And in green, there's a colour that's working around us
0:57:40 > 0:57:42all the time, harvesting sunlight.
0:57:44 > 0:57:48And in violet, there's a reminder of the colours beyond the rainbow.
0:57:49 > 0:57:52Sometimes it's the simplest things in life
0:57:52 > 0:57:54that tell the richest stories
0:57:54 > 0:57:57and to appreciate the stories of colour,
0:57:57 > 0:58:01all you need to do is walk out into the world and look.
0:58:13 > 0:58:17Discover more about the story of the colours of scientific discovery
0:58:17 > 0:58:18with the Open University.
0:58:18 > 0:58:20Go to...
0:58:22 > 0:58:24..and follow the links to the Open University.