0:00:03 > 0:00:05We live in a world ablaze with colour.
0:00:06 > 0:00:11Rainbows and rainforests, oceans and humanity.
0:00:11 > 0:00:13Earth is the most colourful place we know of.
0:00:16 > 0:00:20It's easy to take our colourful world for granted.
0:00:20 > 0:00:23Red, yellow and blue are some of the first words we learn
0:00:23 > 0:00:26but the colours we see are far more complex
0:00:26 > 0:00:29and fascinating than they appear.
0:00:29 > 0:00:31Each one has its own story to tell.
0:00:35 > 0:00:37I'm Dr Helen Czerski.
0:00:37 > 0:00:40I'm a physicist and I'm fascinated by colour.
0:00:41 > 0:00:46In this series, I'm going to uncover exactly what it is, how it
0:00:46 > 0:00:50works and how it has written the story of our planet.
0:00:51 > 0:00:54'I'll seek out the colours that transformed the Earth,
0:00:54 > 0:00:57'from a ball of rock to a vivid jewel...'
0:00:57 > 0:00:59This salt and this colour
0:00:59 > 0:01:03has a little bit more to it than meets the eye.
0:01:03 > 0:01:06'..and the colours that life has used to survive and thrive.'
0:01:08 > 0:01:11So these insects are broadcasting a code. It's almost like Morse code.
0:01:13 > 0:01:15This is communication in colour.
0:01:17 > 0:01:19'And I'm going in search of the colours that
0:01:19 > 0:01:21'exist beyond the rainbow...'
0:01:22 > 0:01:25When we look at it in infrared, it completely lights up.
0:01:25 > 0:01:28We're observing the invisible.
0:01:28 > 0:01:32'..to discover why our future will be shaped by colours our eye
0:01:32 > 0:01:34'can't even perceive.'
0:01:34 > 0:01:39We've developed a completely new technology that can image people.
0:01:39 > 0:01:41That's a huge step forward.
0:01:41 > 0:01:44I'm going to tell our story from an unusual perspective...
0:01:46 > 0:01:49..by looking at 15 colours that made the world and us.
0:02:09 > 0:02:10Just look at all of this.
0:02:10 > 0:02:15Blue lake, green trees, blue sky, red and yellow apple.
0:02:15 > 0:02:18The Earth is a fantastically colourful place.
0:02:22 > 0:02:26These colours emerged deep in the past.
0:02:26 > 0:02:30Each one is a clue to a vital process that has shaped the Earth.
0:02:33 > 0:02:36And each helps answer a fundamental question -
0:02:36 > 0:02:38how did our world come to be this way?
0:02:40 > 0:02:44In this programme, I'm going in search of five colours that
0:02:44 > 0:02:45tell the story of our planet.
0:02:58 > 0:03:01It's a story that begins with light.
0:03:03 > 0:03:06Our planet is bathed in light from our nearest star...
0:03:08 > 0:03:10..the sun.
0:03:10 > 0:03:13When we think of the colour of the sun, we usually think of yellow,
0:03:13 > 0:03:16and it certainly looks yellowish at the moment,
0:03:16 > 0:03:18but it isn't really that colour.
0:03:20 > 0:03:24The yellow hue of the sun conceals the real nature of sunlight.
0:03:26 > 0:03:30Hidden within each sunbeam are the secrets of colour -
0:03:30 > 0:03:32what it is and what it does.
0:03:36 > 0:03:39I'm on my way to a place where I can reveal the essence of sunlight.
0:03:48 > 0:03:51This is the Big Bear Solar Observatory,
0:03:51 > 0:03:54set on a lake in the mountains of Southern California.
0:03:56 > 0:03:58It's the largest solar telescope in the world.
0:04:01 > 0:04:05Professor Dale Gary is director of the observatory.
0:04:05 > 0:04:09The intriguing question is, what makes this unusual spot
0:04:09 > 0:04:12a good place to study the workings of the sun?
0:04:14 > 0:04:17Why would you build an observatory here, in the middle of a lake?
0:04:17 > 0:04:19Here, we want to observe in the daytime,
0:04:19 > 0:04:22and that's when the land would normally be heating up.
0:04:22 > 0:04:25So what we want to do is be in the vicinity of a lake,
0:04:25 > 0:04:29have a nice, cool lake that keeps the sun's heat from heating up
0:04:29 > 0:04:32the atmosphere above it.
0:04:32 > 0:04:34High-altitude lakes are the perfect place to observe the sun.
0:04:39 > 0:04:43For most of human history, people thought sunlight was pure
0:04:43 > 0:04:44and unchangeable.
0:04:45 > 0:04:48The bright orb in the sky bathes the world in light,
0:04:48 > 0:04:50pure, white light.
0:04:52 > 0:04:57But then came one of the biggest revelations in science,
0:04:57 > 0:05:01which came about when Sir Isaac Newton experimented with a prism.
0:05:04 > 0:05:07Isaac Newton was the first person to appreciate
0:05:07 > 0:05:10the significance of a really simple experiment.
0:05:10 > 0:05:13When he did it, he blacked out a room in his house
0:05:13 > 0:05:17and just let in a single sunbeam through a chink in the curtains.
0:05:17 > 0:05:18And in front of that he put a prism,
0:05:18 > 0:05:21something that was relatively new at that time.
0:05:21 > 0:05:23I've got a much more sophisticated set-up here
0:05:23 > 0:05:26because I'm taking advantage of this fantastic solar telescope,
0:05:26 > 0:05:27and this is a modern prism,
0:05:27 > 0:05:31but Isaac Newton would absolutely have recognised this experiment.
0:05:32 > 0:05:35When the light comes through the prism,
0:05:35 > 0:05:37the prism slows it down and it bends it.
0:05:38 > 0:05:42And what Isaac Newton saw coming out of the prism told him
0:05:42 > 0:05:45something really fundamental about the nature of light.
0:05:45 > 0:05:46And it was this.
0:06:00 > 0:06:02This is the visible spectrum,
0:06:02 > 0:06:04from red through orange and yellow
0:06:04 > 0:06:07through green and blue and all the way to violet.
0:06:07 > 0:06:09White light isn't an absence of colour,
0:06:09 > 0:06:13it's all the colours folded in together.
0:06:13 > 0:06:16And what Newton realised is that if you put those components back
0:06:16 > 0:06:19together, you get white light once more.
0:06:19 > 0:06:22But that white light hides within in it all
0:06:22 > 0:06:24the ingredients for our visual world.
0:06:25 > 0:06:27What we'd believed to be pure,
0:06:27 > 0:06:31immutable white light was actually a vivid spectrum.
0:06:32 > 0:06:36At one end, shorter wavelengths of light that we see as blue
0:06:36 > 0:06:38ranging through to the other end,
0:06:38 > 0:06:42longer wavelengths of light that we see as red.
0:06:42 > 0:06:45The combination of different wavelengths of light
0:06:45 > 0:06:49is what creates every hue and shade that we can see.
0:06:49 > 0:06:54It's an amazing thought - that light can't exist without colour...
0:06:56 > 0:06:58..and colour can't exist without light.
0:07:02 > 0:07:06Today, nearly four centuries after Newton's revelation,
0:07:06 > 0:07:09the solar astronomers at Big Bear are able to study
0:07:09 > 0:07:14the sun in intricate detail, helping to reveal another
0:07:14 > 0:07:17fundamental truth about what colour actually is.
0:07:23 > 0:07:25By using filters to look at the sun in all the different
0:07:25 > 0:07:29colours of the spectrum, scientists can detect
0:07:29 > 0:07:33features on its surface that were previously unknown.
0:07:33 > 0:07:35It's a seething, dynamic world
0:07:35 > 0:07:39where vast magnetic fields can spit matter and energy
0:07:39 > 0:07:43out into space, sending them rippling through the solar system.
0:07:44 > 0:07:47So here, we see lots of features here
0:07:47 > 0:07:50that are following the magnetic field, so these linear...
0:07:50 > 0:07:52- They look like twisted ropes, almost. - That's right.
0:07:52 > 0:07:56And the twisting is actually an indication of stored energy.
0:07:56 > 0:07:59They begin to twist and some of it starts to unravel,
0:07:59 > 0:08:02so when they unravel enough, it becomes very sudden
0:08:02 > 0:08:05and you see this flare occur over just a few minutes.
0:08:07 > 0:08:10- Oh, wow!- And then suddenly, the flare is generated.
0:08:11 > 0:08:15This is really thrilling. What I've just seen is a solar flare -
0:08:15 > 0:08:19a massive ejection of electromagnetic energy from the sun.
0:08:21 > 0:08:25These are some of the highest-energy events in our solar system.
0:08:25 > 0:08:29Each one is capable of sending the same energy
0:08:29 > 0:08:33as a billion nuclear bombs hurtling towards our planet.
0:08:37 > 0:08:40So the sun very occasionally launches things out into space
0:08:40 > 0:08:43and if the Earth is in the firing line, we feel their influence.
0:08:43 > 0:08:47That's right. And it can be as often as a couple of times a month.
0:08:51 > 0:08:54When they do arrive, then you can have magnetic disturbances which
0:08:54 > 0:08:58can affect satellite signals and GPS signals...
0:09:01 > 0:09:04..and cellphones and the power grids...
0:09:06 > 0:09:10..and then actually cause great currents to flow and
0:09:10 > 0:09:15destroy transformers, and that can be very bad for a big power system.
0:09:20 > 0:09:22It's easy to think of the sun as just a sort of yellow
0:09:22 > 0:09:25circle in the sky but, in fact, it's a dynamic system. It's doing things
0:09:25 > 0:09:28and it's sending material out in our direction.
0:09:28 > 0:09:29Yes.
0:09:29 > 0:09:32If the sun didn't have magnetic fields and this activity,
0:09:32 > 0:09:35it would be as boring as most astronomers believe it is.
0:09:35 > 0:09:36SHE LAUGHS
0:09:40 > 0:09:44The Earth is bathed in a colossal flood of energy from the sun.
0:09:47 > 0:09:50A tiny part of that energy is the sunlight we see.
0:09:52 > 0:09:56All light, and therefore all colour, carries energy...
0:09:58 > 0:10:01..and the variety of different wavelengths
0:10:01 > 0:10:03leads to another essential truth about colour.
0:10:09 > 0:10:13This is Betelgeuse - a star that's glowing red.
0:10:13 > 0:10:18This colour tells us its temperature is about 3,000 degrees Celsius.
0:10:19 > 0:10:23From this, we know we're looking at an ageing star
0:10:23 > 0:10:25coming to the end of its life.
0:10:27 > 0:10:32And this is Sirius - a star that's glowing blue.
0:10:32 > 0:10:36This colour indicates a temperature of nearly 10,000 degrees,
0:10:36 > 0:10:39so we know it's a younger and hotter star.
0:10:41 > 0:10:46So colour isn't just energy, it's also information,
0:10:46 > 0:10:49and astronomers have learned to read the information
0:10:49 > 0:10:53contained in colour to discover what different stars are made of.
0:10:56 > 0:10:58As Newton first did with his prism,
0:10:58 > 0:11:02they bend the light from a star to break it into its colour spectrum.
0:11:04 > 0:11:06Dark lines in the spectrum
0:11:06 > 0:11:10mark the presence of specific chemical elements,
0:11:10 > 0:11:14each of which absorbs a precise wavelength of coloured light.
0:11:15 > 0:11:19So the pattern of dark lines reveals exactly which
0:11:19 > 0:11:21elements are present in the star.
0:11:26 > 0:11:27And what of our own sun?
0:11:37 > 0:11:41This view from the International Space Station shows how it
0:11:41 > 0:11:43looks to the rest of the universe.
0:11:45 > 0:11:49Here, above Earth's atmosphere, it glows a milky white.
0:11:50 > 0:11:52This is the sun's true colour.
0:11:53 > 0:11:55It's a striking view,
0:11:55 > 0:11:58one that only a handful of humans have seen with their own eyes.
0:12:01 > 0:12:04Below, you can see the sun's reflection on the Earth's
0:12:04 > 0:12:07surface, and it is a rich yellow,
0:12:07 > 0:12:12the colour that we Earthbound humans see when we look at the sun.
0:12:12 > 0:12:15That's because when sunlight reaches the Earth,
0:12:15 > 0:12:17it interacts with our planet's thick atmosphere.
0:12:19 > 0:12:23The blue wavelengths are scattered, making the sky blue...
0:12:26 > 0:12:28..and the sun appear yellow.
0:12:33 > 0:12:38As the sun sets, our view of its colour becomes ever more distorted.
0:12:39 > 0:12:43The atmosphere acts like a giant version of Newton's prism,
0:12:43 > 0:12:47bending the light first to orange then red and,
0:12:47 > 0:12:53if the conditions are just right, a brief and final glimpse of green.
0:12:59 > 0:13:01And in the darkness of night,
0:13:01 > 0:13:06we can perhaps best appreciate the full significance of colour.
0:13:06 > 0:13:09There's a huge richness in the colourful world around us,
0:13:09 > 0:13:12offering all kinds of clues as to what's going on,
0:13:12 > 0:13:13but we can only see those colours
0:13:13 > 0:13:16because there's light shining on them.
0:13:16 > 0:13:20If there's no light, no colour, no information.
0:13:28 > 0:13:31It's only in sunlight that the Earth explodes in colour.
0:13:34 > 0:13:37And there's one colour that seems to dominate our world.
0:13:47 > 0:13:49But the paradox of blue is that
0:13:49 > 0:13:55while it seems to be all around us, very rarely is it solid or tangible.
0:13:56 > 0:13:59Blue's absent from the palate of the land itself
0:13:59 > 0:14:03and scarce in the plants and animals that inhabit it.
0:14:06 > 0:14:10There are exceptions, striking to our eye because they're unusual.
0:14:10 > 0:14:12IT SQUAWKS
0:14:15 > 0:14:18This scarcity meant that our early human ancestors had very
0:14:18 > 0:14:21little contact with the colour blue.
0:14:22 > 0:14:26It's almost entirely absent from ancient art and literature...
0:14:28 > 0:14:32..and many languages still don't have a specific word for it, even today.
0:14:34 > 0:14:37Perhaps that's because it's always out of reach.
0:14:39 > 0:14:41We can't touch the blueness of the sky
0:14:41 > 0:14:44or capture the deep blue of the oceans.
0:14:46 > 0:14:48Yet, in some remote corners,
0:14:48 > 0:14:52the Earth does harbour this elusive colour.
0:14:52 > 0:14:53The way it got there
0:14:53 > 0:14:56provides a clue to how our vivid planet came into existence.
0:15:02 > 0:15:07And to get my hands on it, I'm about to enter a very different world.
0:15:14 > 0:15:17David Margulies is an artist, historian
0:15:17 > 0:15:19and devotee of the colour blue.
0:15:23 > 0:15:27In his London studio, he works with some of the rarest minerals
0:15:27 > 0:15:29and pigments on Earth.
0:15:30 > 0:15:34Among them all, the most spectacular are the blues.
0:15:35 > 0:15:39And one blue in particular takes pride of place on his shelves.
0:15:44 > 0:15:48This is a piece of lapis lazuli that's come from the one
0:15:48 > 0:15:50mountain in Afghanistan.
0:15:50 > 0:15:52So the important thing here is this blue colour
0:15:52 > 0:15:54and that is lapis lazuli.
0:15:54 > 0:15:59It is. It was the most precious and most expensive of all the pigments.
0:15:59 > 0:16:01There aren't many blue things in nature,
0:16:01 > 0:16:05so this must have been a spectacular thing to display and to find.
0:16:05 > 0:16:10Someone had walked through the mountains of Afghanistan
0:16:10 > 0:16:12and come across a blue stone.
0:16:12 > 0:16:17And it makes me wonder whether they believed that the sky had
0:16:17 > 0:16:20fallen to the Earth and turned to rock.
0:16:21 > 0:16:24I love that idea, the sky that had fallen into a rock.
0:16:24 > 0:16:26That's exactly what it looks like, isn't it?
0:16:30 > 0:16:32'The colour is so stunning.
0:16:32 > 0:16:35'I can imagine the impact it must have made when lapis first
0:16:35 > 0:16:39'arrived in Europe, when trade routes from the east opened up.'
0:16:42 > 0:16:44It was seen as extremely valuable.
0:16:44 > 0:16:46In Renaissance Italy it was
0:16:46 > 0:16:50so expensive it was the equivalent of the price of gold.
0:16:50 > 0:16:51To have this was a status symbol
0:16:51 > 0:16:54and the most visible way of having it was to put it on a painting
0:16:54 > 0:16:56cos you could paint this colour onto a big canvas
0:16:56 > 0:16:59and show that you had this commodity.
0:16:59 > 0:17:01So it's not a subtle way of displaying your status.
0:17:01 > 0:17:05- It's saying, for everyone to see... - I don't think it's subtle at all.
0:17:05 > 0:17:08I think the most important aspect is that lapis
0:17:08 > 0:17:10does have a slightly mystical quality.
0:17:15 > 0:17:17So, when it came to painting,
0:17:17 > 0:17:19quite often the blue was used
0:17:19 > 0:17:22to paint the robes of Mary.
0:17:23 > 0:17:27Probably the most famous artist to have used it is Titian.
0:17:29 > 0:17:32'There's something entrancing about this colour,
0:17:32 > 0:17:36'but to discover what it can tell us about our planet,
0:17:36 > 0:17:38'I need to do what painters do,
0:17:38 > 0:17:40'and get right inside this rock.'
0:17:42 > 0:17:45An artist is presented with a lump of this rock,
0:17:45 > 0:17:48and they have to make paint out of it. What do they do?
0:17:48 > 0:17:50- They hammer it. - Not very sophisticated.
0:17:50 > 0:17:53Hammer it until it gets smaller and smaller.
0:17:57 > 0:18:00It's quite satisfying, this.
0:18:02 > 0:18:05This is the first time it's been a colour cos this has never seen daylight before.
0:18:05 > 0:18:07That bit of rock I've just smashed has just become
0:18:07 > 0:18:09a colour for the first time.
0:18:09 > 0:18:12So the next one along... So now we've got a lot of broken up bits,
0:18:12 > 0:18:16- and you can start to see blue powder...- That's right.
0:18:16 > 0:18:18..and that's what the pigment is, it's the powder,
0:18:18 > 0:18:21- when it becomes a powder. - That's right.
0:18:23 > 0:18:26It's a horrible noise. It's such a horrible noise.
0:18:26 > 0:18:28You might smell it as well.
0:18:28 > 0:18:32Oh! There's a really strong smell of sulphur.
0:18:32 > 0:18:35It is sulphur. Sulphur is what makes the rock blue.
0:18:36 > 0:18:37And then the final stage,
0:18:37 > 0:18:41when it's broken down, is what we've got in the last one here.
0:18:41 > 0:18:43This is the bluest thing I've ever seen.
0:18:45 > 0:18:48'It's the chemistry of this rock that creates its colour.
0:18:50 > 0:18:53'Sulphur more often produces yellowish compounds...
0:18:53 > 0:18:56This is lovely, lovely stuff.
0:18:56 > 0:18:59'..but in lapis lazuli, the unique combination of sulphur with
0:18:59 > 0:19:05'other elements, produces this deep, rich blue we call ultramarine.'
0:19:15 > 0:19:18And this is it. This is the final step.
0:19:19 > 0:19:23The blue powder has been mixed with oil and some wax
0:19:23 > 0:19:25and it's a paint.
0:19:25 > 0:19:28And so this rock that looks like it fell from the sky
0:19:28 > 0:19:29is becoming sky all over again.
0:19:33 > 0:19:36When we look at this, we just see a blue rock,
0:19:36 > 0:19:40but the secret to that colour is hidden in the atoms
0:19:40 > 0:19:42that make this up.
0:19:42 > 0:19:45But the atoms themselves aren't enough.
0:19:45 > 0:19:49To get this you need to transform them.
0:19:49 > 0:19:52For a transformation to this dramatic blue
0:19:52 > 0:19:55you need the sorts of pressures and temperatures
0:19:55 > 0:19:57with which planets are forged.
0:20:20 > 0:20:25Humans have made lapis a part of our culture in exquisite, delicate ways.
0:20:25 > 0:20:27But its origins couldn't be more different,
0:20:27 > 0:20:30and they're certainly a very long way from a sophisticated art gallery.
0:20:35 > 0:20:39'I've come high into the mountains of Southern California,
0:20:39 > 0:20:43'one of the few places on the planet where lapis lazuli can be found.
0:20:46 > 0:20:49'It takes a unique set of conditions to produce the vivid colour
0:20:49 > 0:20:51'of this rock,
0:20:51 > 0:20:53'and Professor George Rossman,
0:20:53 > 0:20:57a geologist at the California Institute of Technology,
0:20:57 > 0:21:00'is going to help me understand how it formed.'
0:21:00 > 0:21:03Here's an example. The blue is kind of interesting.
0:21:03 > 0:21:04It comes from sulphur.
0:21:04 > 0:21:07The important thing is we have to get three sulphur atoms,
0:21:07 > 0:21:10and we have to line them up in a row - one, two, three atoms in a chain,
0:21:10 > 0:21:14trapped inside a cage inside the mineral, to make this happen.
0:21:18 > 0:21:21'It takes extreme temperatures
0:21:21 > 0:21:25'and pressures to force sulphur atoms to combine in this particular way.
0:21:25 > 0:21:30'So the very existence of this rock is a telltale sign of the powerful
0:21:30 > 0:21:35'forces that formed our planet, and are still at work deep within it.'
0:21:35 > 0:21:38When we look at this, we see this amazing colour,
0:21:38 > 0:21:41and everyone loves looking at it, but, really, what we're looking at is
0:21:41 > 0:21:45evidence, direct evidence, that this was deep down in the Earth's crust.
0:21:45 > 0:21:48Oh, this has been down in the cauldron of geological fire,
0:21:48 > 0:21:50down 35km, 40km below the surface.
0:21:50 > 0:21:54And then that has to get taken into a really active geological area
0:21:54 > 0:21:56to be heated up.
0:21:56 > 0:22:00Molten rock came in, rock like this one right here,
0:22:00 > 0:22:04and then the heat from this rock started a series of chemical reactions.
0:22:04 > 0:22:06So it's a very specific type of oven, that.
0:22:06 > 0:22:07Oh, yes.
0:22:07 > 0:22:09So it would have been red hot that deep down,
0:22:09 > 0:22:11and then as it came up it became blue.
0:22:11 > 0:22:14Absolutely correct. Through earthquakes and tectonic activity
0:22:14 > 0:22:18these rocks have been slowly brought up over tens of millions of years,
0:22:18 > 0:22:20so they're now 2km to 3km above sea level.
0:22:20 > 0:22:22It's an amazing process.
0:22:29 > 0:22:33This rock has been deep down into the Earth's crust
0:22:33 > 0:22:37and it's been transformed by the processes that shape our planet.
0:22:37 > 0:22:39And its colour is a reminder of that.
0:22:40 > 0:22:43It's appropriate that that colour is blue, perhaps,
0:22:43 > 0:22:45because we live on a blue planet.
0:22:48 > 0:22:52'Just how dominant this colour truly is, is a fairly recent discovery.
0:22:53 > 0:22:55'It's only within the past 60 years,
0:22:55 > 0:23:01'when humans got into space and gained the ability to look back at ourselves,
0:23:01 > 0:23:04'that we've been able to see our planet in its colourful entirety.
0:23:06 > 0:23:11'A single photograph, taken a quarter of a million miles from Earth,
0:23:11 > 0:23:14'changed our view of our home, forever.
0:23:16 > 0:23:19'On Christmas Eve, 1968,
0:23:19 > 0:23:23'as Apollo Eight made its way around the dark side of the Moon,
0:23:23 > 0:23:26'astronaut Bill Anders picked up his camera
0:23:26 > 0:23:28'and began to take pictures.'
0:23:31 > 0:23:33I just clicked away and just kept turning,
0:23:33 > 0:23:36and I took at least a dozen, maybe 50 pictures,
0:23:36 > 0:23:40one of which was selected by others to be Earthrise.
0:23:41 > 0:23:43'This is phenomenal.'
0:23:43 > 0:23:48Out of the lunar horizon came this beautiful blue.
0:23:50 > 0:23:52'Earthrise depicted our home planet
0:23:52 > 0:23:56'in a way that nobody back on Earth had ever seen before...
0:23:58 > 0:24:01'Let there be light. And there was light.'
0:24:03 > 0:24:06'..a planet dominated by the colour blue.'
0:24:09 > 0:24:13Even though we were hard-bitten test and fighter pilots,
0:24:13 > 0:24:15this thing was beautiful.
0:24:16 > 0:24:19'Our home is defined by this single colour.
0:24:21 > 0:24:24'A vibrant blue orb,
0:24:24 > 0:24:27'suspended against the blackness of the cosmos.
0:24:32 > 0:24:35'It's from this vast expanse of space
0:24:35 > 0:24:38'that one of our most celebrated colours emerged.
0:24:40 > 0:24:43'It's a colour we've worshipped for millennia.
0:24:44 > 0:24:46'Wars have been fought over it,
0:24:46 > 0:24:50'and yet its very presence on the face of the Earth is an accident.
0:24:52 > 0:24:54'There's an extraordinary story here,
0:24:54 > 0:24:58'one that reveals the next great force that shaped our planet.
0:25:11 > 0:25:13'And to tell it,
0:25:13 > 0:25:16'I'm going to start somewhere most of us would never normally get to see.'
0:25:19 > 0:25:22I'm somewhere close to central London, but I can't tell you where
0:25:22 > 0:25:25and that's because I'm on my way to a secret location.
0:25:30 > 0:25:33'I'm about to get my hands on this most precious
0:25:33 > 0:25:35'and mysterious of colours.'
0:25:39 > 0:25:42It's worth all the secrecy when you get to this.
0:25:42 > 0:25:45It's absolutely unmistakable.
0:25:45 > 0:25:48There's only one metal that's this colour,
0:25:48 > 0:25:50and it's gold.
0:25:50 > 0:25:54This is very, very pure gold. It's 99.99% pure
0:25:54 > 0:25:57and it's also frighteningly valuable.
0:25:57 > 0:26:02At today's prices, it's apparently worth £26,000.
0:26:02 > 0:26:05You can see why humans value this so much.
0:26:06 > 0:26:08It is stunningly beautiful.
0:26:10 > 0:26:15'The secret of gold's mesmerising colour comes from its chemistry.
0:26:15 > 0:26:18'Gold atoms reflect yellow and red wavelengths,
0:26:18 > 0:26:21'producing a deep, rich yellow,
0:26:21 > 0:26:25'that's accentuated by gold's metallic shine.
0:26:27 > 0:26:30'This unique combination of factors
0:26:30 > 0:26:33'makes it seem like gold is generating a warm light of its own.
0:26:35 > 0:26:39'It's this property that's enchanted us since ancient times.
0:26:42 > 0:26:44'But it's only due to an accident of history,
0:26:44 > 0:26:48'that we're able to get our hands on gold at all.
0:26:48 > 0:26:50'The story of this precious colour
0:26:50 > 0:26:53'reveals one of the most dramatic events that shaped our planet.
0:26:59 > 0:27:03'Gold didn't exist when the universe was first formed.
0:27:03 > 0:27:06'To make gold and other heavy metals,
0:27:06 > 0:27:09'it took unimaginably powerfully forces
0:27:09 > 0:27:12'to fuse the atoms of lighter elements together.
0:27:12 > 0:27:16'Perhaps the explosion of a supernova, a dying star.
0:27:21 > 0:27:24'Or perhaps, as recent research has suggested,
0:27:24 > 0:27:28'the colossal energy of two neutron stars,
0:27:28 > 0:27:31'tearing each other apart to form a black hole.
0:27:37 > 0:27:39'In the early solar system,
0:27:39 > 0:27:42'there was a sprinkling of this newly forged metal
0:27:42 > 0:27:46'in the swirling mass of dust that would eventually form the planets.
0:27:51 > 0:27:54'But this is where the story of gold becomes really intriguing.'
0:28:00 > 0:28:03Most of the time when we pick up gold, a necklace or a bracelet,
0:28:03 > 0:28:08it's something small, and so you don't really notice how heavy it is.
0:28:08 > 0:28:11But with these, it's really noticeable that they're really,
0:28:11 > 0:28:12really heavy.
0:28:13 > 0:28:15We've all heard someone say
0:28:15 > 0:28:17that a person is worth their weight in gold.
0:28:17 > 0:28:22Well, this is the pile of gold that weighs the same as me.
0:28:22 > 0:28:26It's worth £1.6 million.
0:28:26 > 0:28:28The thing is, it's quite a small pile.
0:28:28 > 0:28:31It doesn't take up nearly as much space as I do.
0:28:31 > 0:28:35It's been squashed down, so it only fills up a very small space.
0:28:35 > 0:28:38Each individual gold atom is very, very big,
0:28:38 > 0:28:42but the consequence is that gold is very dense and very heavy.
0:28:44 > 0:28:48'But I shouldn't be able to hold this dense metal in my hands
0:28:48 > 0:28:52'because gold shouldn't really exist on the surface of the planet at all.
0:28:55 > 0:28:58'The early Earth was a ball of molten rock.
0:29:00 > 0:29:02'In these furnace temperatures,
0:29:02 > 0:29:05'gold and other metals existed as a viscous molten mass.
0:29:07 > 0:29:09'Over tens of millions of years,
0:29:09 > 0:29:12'this mixture of metals sank,
0:29:12 > 0:29:17'dragging gold deep into the Earth's core,
0:29:17 > 0:29:19'thousands of miles beyond our reach.
0:29:27 > 0:29:30'And yet, in certain places on Earth,
0:29:30 > 0:29:33'gold lies tantalisingly close to the surface...
0:29:35 > 0:29:38'..just waiting to be plucked from the ground.'
0:29:44 > 0:29:46This is Jamestown in California,
0:29:46 > 0:29:50and it's a town that's got gold woven through its history.
0:29:51 > 0:29:54In the hills about 80 miles north of here,
0:29:54 > 0:29:56in 1848,
0:29:56 > 0:30:01James W Marshall saw the first glint of gold in California.
0:30:02 > 0:30:03As the news spread,
0:30:03 > 0:30:07hundreds of thousands of people flooded here,
0:30:07 > 0:30:09seeking their fortune,
0:30:09 > 0:30:13each desperately hoping to see that same golden glimmer.
0:30:13 > 0:30:16It became known as the California Gold Rush.
0:30:25 > 0:30:29'But if gold did sink deep into Earth's core,
0:30:29 > 0:30:33'where did the gold that fuelled the California Gold Rush come from?
0:30:35 > 0:30:41'Steve Mojzsis is Professor of Geology at the University of Colorado
0:30:41 > 0:30:43'and he's brought with him a clue that points
0:30:43 > 0:30:47'to an exotic and violent origin for the gold we find on Earth...'
0:30:48 > 0:30:52This one fell in Siberia in 1947.
0:30:52 > 0:30:54'..a fragment of a meteorite.'
0:30:57 > 0:31:00A very interesting story emerges.
0:31:00 > 0:31:03Meteorites are the leftovers of planet formation.
0:31:03 > 0:31:08In a sense they're a chemical museum of the early Solar System.
0:31:08 > 0:31:10What's inside a meteorite, then?
0:31:10 > 0:31:15What they contain are all of the elements that go into making the Earth,
0:31:15 > 0:31:17including abundant gold.
0:31:21 > 0:31:24So there were meteorites flying around the solar system
0:31:24 > 0:31:25full of precious metals?
0:31:25 > 0:31:29That's correct, and occasionally these would have struck the Earth.
0:31:33 > 0:31:36So we think it was meteorites that delivered the precious
0:31:36 > 0:31:40cargo of gold to Earth's surface early in its history.
0:31:42 > 0:31:45'Many scientists think there's only one explanation
0:31:45 > 0:31:48'for the presence of gold near the Earth's surface.
0:31:49 > 0:31:54'It had to be transported here from outer space
0:31:54 > 0:31:57'during an intense period of meteorite
0:31:57 > 0:32:00'and comet bombardment nearly four billion years ago.
0:32:02 > 0:32:06'This violent event left scars across our Solar System,
0:32:06 > 0:32:10'including many of the craters that we can still see on the surface of the Moon.
0:32:15 > 0:32:18'The craters left on Earth have long since gone,
0:32:18 > 0:32:21'worn away by tectonic movement, weathering and erosion.
0:32:22 > 0:32:25'But what the meteorites brought with them remains.'
0:32:27 > 0:32:30Here's the Earth, all well-separated
0:32:30 > 0:32:32with all of the metals where
0:32:32 > 0:32:34they're supposed to be in the core,
0:32:34 > 0:32:37and then this planet was salted
0:32:37 > 0:32:43with meteorite debris that brought metals with it, including gold.
0:32:43 > 0:32:48That's the surprising conclusion of the origin of gold to Earth's surface.
0:32:54 > 0:32:56Even though the planet had a new supply of gold,
0:32:56 > 0:33:00there wasn't anything to see because it was just too dilute.
0:33:00 > 0:33:04The gold that there was, was a tiny fraction of the Earth's crust
0:33:04 > 0:33:07and it was spread out around the planet. It was really rare.
0:33:08 > 0:33:11And yet, billions of years later,
0:33:11 > 0:33:16a human could just pick up a nugget of gold out of the landscape.
0:33:16 > 0:33:20To get from one to the other, the planet had one final trick to play.
0:33:26 > 0:33:30'With only one gram of gold for every thousand tonnes of the Earth's
0:33:30 > 0:33:33'crust, there had to be a way to concentrate the tiny
0:33:33 > 0:33:36'particles of gold, into the colour we see today.
0:33:41 > 0:33:45'And across the surface of the planet is something that can do just that.
0:33:48 > 0:33:50'In the streams around Jamestown,
0:33:50 > 0:33:54'prospector Brent Shock relies on the properties of water
0:33:54 > 0:33:58'to seek his fortune, just like the original Gold Rush pioneers.
0:34:00 > 0:34:03'In doing so, he's mimicking the planetary processes
0:34:03 > 0:34:05'that finally brought us gold.'
0:34:08 > 0:34:09Just sprinkle a little in here.
0:34:09 > 0:34:11So this is just dirt from the side there?
0:34:11 > 0:34:13This is it. Yeah.
0:34:13 > 0:34:14So it's like a little ladder here
0:34:14 > 0:34:16and the stream's bouncing over the ladder?
0:34:16 > 0:34:19- It creates a low-pressure area. Water slows, gold drops.- Yes.
0:34:19 > 0:34:21You've got your crevices here.
0:34:21 > 0:34:24You've got your low-pressure areas there with the ripples.
0:34:26 > 0:34:28And if it's dancing a little bit,
0:34:28 > 0:34:30the gold can work its way down
0:34:30 > 0:34:32and they will grab hold of the fine gold.
0:34:32 > 0:34:35So it's getting caught just behind these ridges?
0:34:35 > 0:34:36Exactly.
0:34:38 > 0:34:41And then you just look through this and look for the colour?
0:34:41 > 0:34:44- Yeah, we look, we don't put our fingers in.- Oh. really?
0:34:44 > 0:34:47THEY LAUGH That's me told, isn't it!
0:34:47 > 0:34:48So this looks really simple,
0:34:48 > 0:34:51but actually there's a very sophisticated thing going on.
0:34:51 > 0:34:53You're the scientist.
0:34:55 > 0:34:59- A stream can replicate, naturally, this set-up here?- Yeah.
0:34:59 > 0:35:03Constantly rolling. Constantly rising and settling.
0:35:03 > 0:35:05Every time the water rises and then starts,
0:35:05 > 0:35:08you can come out here a find gold laying on the bedrock.
0:35:08 > 0:35:10Almost a renewable resource.
0:35:10 > 0:35:12So we keep shovelling this stuff in.
0:35:15 > 0:35:17You want to look at the gold.
0:35:17 > 0:35:18Is it coarse, is it smooth?
0:35:18 > 0:35:21The smoother it is, the farther it's travelled.
0:35:21 > 0:35:22Then you want to triangulate your way up
0:35:22 > 0:35:25to find out where the vein is, where the source is.
0:35:25 > 0:35:29That's what everybody wants, the source of what's feeding this.
0:35:32 > 0:35:36'Over millions of years, water picked up gold,
0:35:36 > 0:35:38'transported, sorted,
0:35:38 > 0:35:41'and concentrated it,
0:35:41 > 0:35:45'and then deposited in a form that made it easier for us to find.
0:35:46 > 0:35:48It's a process that's still happening,
0:35:48 > 0:35:51'and drives our continued obsession
0:35:51 > 0:35:54'with one of Earth's most alluring colours.'
0:35:58 > 0:36:02This spectacular colour has been on quite a journey.
0:36:02 > 0:36:05These atoms have travelled from a distant star in time to be
0:36:05 > 0:36:07there for the birth of the solar system.
0:36:07 > 0:36:10And then they hit the Earth in an impact which left a golden
0:36:10 > 0:36:12signature on our landscape.
0:36:12 > 0:36:14And even then it didn't stop,
0:36:14 > 0:36:16because there were sorting processes,
0:36:16 > 0:36:19first by geology and then by water,
0:36:19 > 0:36:22until humans could pluck nuggets like this from the landscape.
0:36:22 > 0:36:24And still it carries on,
0:36:24 > 0:36:27because there are atoms from Egyptian jewellery
0:36:27 > 0:36:29or Inca trinkets that are almost certainly
0:36:29 > 0:36:32part of modern wedding rings or gold bullion.
0:36:35 > 0:36:37So the cycling carries on,
0:36:37 > 0:36:41but this fantastic colour stays exactly the same.
0:36:48 > 0:36:51'It's amazing to think that we would never have seen the colour gold
0:36:51 > 0:36:53'if it wasn't for the action of water.
0:36:56 > 0:36:59'But water has shaped our planet in more fundamental ways.
0:37:00 > 0:37:03'Some of its powers we can witness for ourselves...
0:37:07 > 0:37:11'..but others, no less important, are hidden from view.
0:37:13 > 0:37:15'And to show you,
0:37:15 > 0:37:18'I've come to one of the driest places on Earth
0:37:18 > 0:37:20'in search of one particular colour.'
0:37:31 > 0:37:34I'm 2km up above the floor of Death Valley,
0:37:34 > 0:37:37here in the USA, looking out over this tremendous view.
0:37:39 > 0:37:43It looks like an alien landscape, but there's a colour down there
0:37:43 > 0:37:47which has a huge amount to tell us about things we see every day.
0:37:48 > 0:37:53We think of white as a colour of innocence and purity,
0:37:53 > 0:37:56but down there, in this harsh landscape,
0:37:56 > 0:37:59those white streaks have two stories to tell.
0:38:00 > 0:38:03The first is the story of the tiny,
0:38:03 > 0:38:07of how this colour works and why it's so common.
0:38:07 > 0:38:11And the second is the story of the gigantic,
0:38:11 > 0:38:14because the way that this colour is concentrated here
0:38:14 > 0:38:18is a reminder of the scale of the processes that sculpt our planet
0:38:18 > 0:38:21and paint vast swathes of it in specific colours.
0:38:33 > 0:38:37From that fabulous viewpoint, I'm driving down into the valley,
0:38:37 > 0:38:41to a place with a fantastic name. It's called the Badwater Basin
0:38:41 > 0:38:42and it's very, very low down.
0:38:42 > 0:38:45It's not just the lowest place in this valley,
0:38:45 > 0:38:47it's the lowest place in all of North America,
0:38:47 > 0:38:51and the bottom of it is 85m below sea level.
0:39:09 > 0:39:13This is what I could see from above the valley and it's salt.
0:39:13 > 0:39:16There are hundreds of square kilometres of it here.
0:39:16 > 0:39:18It's just sodium chloride,
0:39:18 > 0:39:20what you'd find on your dinner table,
0:39:20 > 0:39:24but this salt, and this colour, has a little bit more to it than meets the eye.
0:39:30 > 0:39:34'As far as I can see, and crunching under my boots,
0:39:34 > 0:39:38'is what appears to be a solid carpet of brilliant white.
0:39:42 > 0:39:44'But look at this salt more closely
0:39:44 > 0:39:46'and something strange happens.'
0:39:48 > 0:39:50Here it is, a handful of salt,
0:39:50 > 0:39:53and it's bright white, just like all the salt around me.
0:39:53 > 0:39:54But the salt isn't t really white,
0:39:54 > 0:39:58and we can see its true nature if we look at it under a microscope.
0:39:58 > 0:40:00And then this little camera
0:40:00 > 0:40:03is projecting an image onto the screen here.
0:40:03 > 0:40:06And what you can see is that each little crystal is a square
0:40:06 > 0:40:08and that's because the salt crystals are cubes.
0:40:08 > 0:40:12They've got flat edges. There's an orange card behind
0:40:12 > 0:40:15and we can see that orange card through these crystals.
0:40:15 > 0:40:18Light is going straight through them and coming straight back out.
0:40:18 > 0:40:21And what that tells us is that these crystals aren't white,
0:40:21 > 0:40:23they're completely transparent.
0:40:25 > 0:40:27'We don't see the colour of the card any differently,
0:40:27 > 0:40:30'whether a salt crystal is in the way or not.
0:40:32 > 0:40:34'White light from the sun comes in,
0:40:34 > 0:40:37'and orange light bounces back from the card to our eyes.'
0:40:40 > 0:40:42So if the crystals themselves don't have any colour at all,
0:40:42 > 0:40:49why is it that my little pile of salt here, and all of this, looks white?
0:40:49 > 0:40:50Well, we can see why
0:40:50 > 0:40:53if we start to move the microscope to where there's a big pile of them.
0:40:53 > 0:40:56If you've got a stack of crystals all together,
0:40:56 > 0:40:59the light comes in and it's bent as it passes through the first
0:40:59 > 0:41:01crystal and then bent again as it passes through the second crystal.
0:41:01 > 0:41:04And so it zigzags its way through the pile of salt,
0:41:04 > 0:41:07and it eventually it finds its way out to our eyes.
0:41:09 > 0:41:11'With a pile of salt crystals,
0:41:11 > 0:41:16'the sunlight bounces around inside them and never reaches the orange card,
0:41:16 > 0:41:20'so its orange colour remains hidden beneath and never gets to our eyes.'
0:41:22 > 0:41:25White light went in, bounced around, and white light came out,
0:41:25 > 0:41:27and that's why we see salt as white.
0:41:32 > 0:41:35'It isn't just salt that's white because of this.
0:41:38 > 0:41:41'Many things we see as white on a big scale
0:41:41 > 0:41:44'are actually made up of tiny, transparent components.
0:41:47 > 0:41:50'Clouds are small particles of colourless water
0:41:50 > 0:41:52'suspended in colourless air.
0:41:56 > 0:41:58'The white foam of breaking waves
0:41:58 > 0:42:01'is just a turbulent mixture of water and air.
0:42:07 > 0:42:11'And snow is made up of tiny, colourless ice crystals.
0:42:24 > 0:42:27'In fact anything transparent that's small enough
0:42:27 > 0:42:30'to bounce sunlight around on a tiny scale,
0:42:30 > 0:42:31'like these bubbles,
0:42:31 > 0:42:33'will look white on a bigger scale.
0:42:41 > 0:42:45'But the secret of the colour white is just the beginning of what
0:42:45 > 0:42:47'this landscape can reveal.
0:42:48 > 0:42:51'Even the presence of this mass of white salt
0:42:51 > 0:42:54'tells us a much bigger story about our planet.
0:42:57 > 0:43:01'Geologist Garry Hayes has spent years working in Death Valley
0:43:01 > 0:43:04'and studying the process by which these salt flats formed.'
0:43:08 > 0:43:12We're in the hottest, driest place in the entire Northern Hemisphere.
0:43:12 > 0:43:16- And the windiest, it feels like. - And the windiest, it feels like.
0:43:16 > 0:43:19So, I'm just going to pick a bit up here.
0:43:19 > 0:43:22What's quite striking is that this is just mud,
0:43:22 > 0:43:25and then there's this layer of salt on top just like icing.
0:43:25 > 0:43:29- Exactly.- This feels wet to me but that's brine.- It is wet.
0:43:29 > 0:43:31- It's very salty.- It is wet, but it's drying quickly.
0:43:31 > 0:43:32SHE LAUGHS
0:43:34 > 0:43:37And every two or three years you would be standing in a lake
0:43:37 > 0:43:39right now, a foot or two deep of water.
0:43:41 > 0:43:44The water evaporates, the salt stays.
0:43:44 > 0:43:47This salt has been accumulating in this one low area
0:43:47 > 0:43:49for the last couple of million years.
0:43:52 > 0:43:56'So even here, in one of the driest places on Earth,
0:43:56 > 0:43:59'it's water that has shaped and coloured the landscape.
0:44:01 > 0:44:06'Water collects here at Badwater Basin from a vast area all around.
0:44:06 > 0:44:09'There's no lower point it can flow to.
0:44:09 > 0:44:13'so under the baking sun, there's only one place it can go -
0:44:15 > 0:44:16'Up.'
0:44:19 > 0:44:22So, water brought the salt here, but where did the water come from?
0:44:22 > 0:44:26There is a vast amount of ground water underneath this region,
0:44:26 > 0:44:29especially underneath these mountains, so water actually travels
0:44:29 > 0:44:32and trickles through the mountains rather than around them.
0:44:32 > 0:44:34The mountains around us formed between 300
0:44:34 > 0:44:37and 600 million years ago on the bottom of the sea.
0:44:37 > 0:44:40And these rocks have been pushed up and they've been eroded,
0:44:40 > 0:44:43and there are small amounts of salt in the rocks themselves.
0:44:43 > 0:44:46So the salt dissolves into the water as the water's flowing here?
0:44:46 > 0:44:47Absolutely, yes.
0:44:47 > 0:44:49And when it gets here, the salt has nowhere else to go?
0:44:49 > 0:44:51It has nowhere else to go.
0:44:51 > 0:44:54- And it's sitting right below us, right now?- It is.
0:44:58 > 0:45:00'Here on Death Valley's salt flats,
0:45:00 > 0:45:04'the forces that shaped and painted our planet are still in play.
0:45:08 > 0:45:12'Every year, about 5cm of rain falls,
0:45:12 > 0:45:15'but the evaporation rate is so high,
0:45:15 > 0:45:18'it could remove a lake 4m deep in that time.
0:45:21 > 0:45:23'So the salt flats continue to grow.
0:45:25 > 0:45:30'Beneath my feet is a staggering 3km of salty sediment.
0:45:31 > 0:45:34'The intense sun dries out the surface,
0:45:34 > 0:45:37'creating this vivid layer of white.'
0:45:40 > 0:45:42Look out at this enormous valley
0:45:42 > 0:45:45and imagine the slow geological
0:45:45 > 0:45:50processes that have shifted and transformed it over eons.
0:45:50 > 0:45:53And in this, the place of extremes,
0:45:53 > 0:45:56incredibly hot, incredibly dry,
0:45:56 > 0:45:58and way below sea level,
0:45:58 > 0:46:01those processes have concentrated one colour.
0:46:02 > 0:46:08But the details of that colour come from the tiny shape of the crystals.
0:46:08 > 0:46:13So you need both the minuscule and the gigantic to generate this,
0:46:13 > 0:46:15the purest of colours.
0:46:26 > 0:46:31'Our planet's story is captured in the colours it has forged.
0:46:31 > 0:46:35'In blue, we see the sheer power of the forces that heaved within
0:46:35 > 0:46:39'the young Earth, creating mountains and continents.
0:46:44 > 0:46:47'Gold bears witness to a time when meteorites crashed to Earth
0:46:47 > 0:46:50'with a cargo of riches, '
0:46:50 > 0:46:52that changed our planet forever.
0:46:55 > 0:47:00'The dazzling white of salt crystals reveals water as a hidden force,
0:47:00 > 0:47:03'sculpting the face of the Earth in unseen ways.
0:47:06 > 0:47:10'But there's one more colour that can reveal our planet's final
0:47:10 > 0:47:12'and most vital transformation...
0:47:15 > 0:47:18'..the one that led to life
0:47:18 > 0:47:20'and, ultimately, to us.'
0:47:39 > 0:47:41Deep underground isn't the sort of place you would expect to go
0:47:41 > 0:47:43looking for a colour.
0:47:43 > 0:47:46This colour has only been present for half of Earth's history,
0:47:46 > 0:47:49but once it did appear, it appeared on a massive scale.
0:47:53 > 0:47:56Hidden right beneath my feet is a colour that represents
0:47:56 > 0:47:59one of the biggest transitions in Earth's history.
0:48:03 > 0:48:06'I've come to Clearwell Caves in the Forest of Dean,
0:48:06 > 0:48:10'a natural cave system, which extends for 30km
0:48:10 > 0:48:13'under the Gloucestershire countryside.
0:48:13 > 0:48:17'These caves have been mined for more than 4,000 years,
0:48:17 > 0:48:21'since the earliest human societies settled in this part of the world.
0:48:33 > 0:48:35'The substance those miners were digging for
0:48:35 > 0:48:39'is a clue to a remarkable event that transformed Earth
0:48:39 > 0:48:40'more than two billion years ago.'
0:48:46 > 0:48:49Thousands of miners have been down here
0:48:49 > 0:48:52and some of them were looking for this, and this is iron ore.
0:48:52 > 0:48:55It's got tremendous potential for civilisation.
0:48:55 > 0:48:58Just think of all the things you can turn this into.
0:48:58 > 0:49:01A knife or armour or an ornament,
0:49:01 > 0:49:03or, later on, a Spitfire.
0:49:03 > 0:49:07Tools for neurosurgery or a steam engine.
0:49:07 > 0:49:09But this isn't a particularly colourful rock
0:49:09 > 0:49:11and it's not what I've come down here to see.
0:49:18 > 0:49:22'Another material has been mined here for far longer than iron ore.
0:49:25 > 0:49:28'It comes from the same rock, but whilst iron ore is dull
0:49:28 > 0:49:30'metallic grey,
0:49:30 > 0:49:33'the same can't be said for its colourful cousin.'
0:49:41 > 0:49:44This is it. This is red ochre
0:49:44 > 0:49:47and it's a really dramatic colour. You don't expect to see
0:49:47 > 0:49:51something this striking down in a dark cave like this.
0:49:51 > 0:49:54It's actually quite disconcerting sitting here because,
0:49:54 > 0:49:59sitting in this hollow of red is a bit like sitting in the mouth of a monster.
0:49:59 > 0:50:02It's no coincidence that the iron ore
0:50:02 > 0:50:05and the red ochre are found in the same caves,
0:50:05 > 0:50:08because to get vast quantities of this red,
0:50:08 > 0:50:11what you need is iron and then one very specific molecule.
0:50:17 > 0:50:20'With iron filings
0:50:20 > 0:50:23'and some salty water,
0:50:23 > 0:50:26'it's a process that's remarkably easy to replicate.'
0:50:35 > 0:50:38To get this fabulous red colour from grey iron filings,
0:50:38 > 0:50:40the trick is to add oxygen.
0:50:42 > 0:50:45I just sped it up a little bit, but, basically, adding the water
0:50:45 > 0:50:47and a little bit of salt makes the iron
0:50:47 > 0:50:50and the oxygen react together a little bit faster.
0:50:50 > 0:50:54Because all this is, is a beaker of rust.
0:50:54 > 0:50:56And so the combination of oxygen
0:50:56 > 0:50:58and iron has just turned this red very, very quickly.
0:50:58 > 0:51:01But it's also, over geological time,
0:51:01 > 0:51:03what's turned all of these rocks red.
0:51:08 > 0:51:10'Go back three billion years
0:51:10 > 0:51:14'and the formation of these rocks would have been impossible.
0:51:15 > 0:51:19'That's because the atmosphere lacked one crucial ingredient -
0:51:19 > 0:51:21'oxygen.
0:51:21 > 0:51:24'The fact that these red rocks are here today
0:51:24 > 0:51:27'is a clue to, perhaps, the most fundamental change
0:51:27 > 0:51:29'in our planet's history.
0:51:29 > 0:51:31'The arrival of oxygen created an atmosphere
0:51:31 > 0:51:33'that could sustain complex life.
0:51:36 > 0:51:39'With me deep underground is Dr Corinna Abesser.
0:51:40 > 0:51:43'She's an expert in the chemistry of Earth's atmosphere
0:51:43 > 0:51:47'and water systems, and how they've changed over time.'
0:51:48 > 0:51:51The Earth would have been a very different place back then.
0:51:51 > 0:51:54The atmosphere would have been mostly carbon dioxide.
0:51:54 > 0:51:58And back then, there was iron actually in the water of the ocean?
0:51:58 > 0:52:02The ocean would contain a lot of dissolved iron.
0:52:02 > 0:52:06So even though this is our own planet, this was a very alien world.
0:52:06 > 0:52:08Acidic oceans with dissolved iron
0:52:08 > 0:52:11and a horrible atmosphere, by our standards.
0:52:16 > 0:52:18'And then something changed,
0:52:18 > 0:52:20'that changed all that chemistry.'
0:52:21 > 0:52:24So around three billion years ago,
0:52:24 > 0:52:26new organisms developed called cyanobacteria.
0:52:30 > 0:52:32And they used all the ingredients that
0:52:32 > 0:52:37existed in abundance at the time, namely carbon dioxide,
0:52:37 > 0:52:39water and sunlight,
0:52:39 > 0:52:41to produce energy, food.
0:52:41 > 0:52:44And a waste product of that is oxygen.
0:52:47 > 0:52:51'Cyanobacteria are microscopically tiny organisms
0:52:51 > 0:52:54'that evolved in the early oceans.
0:52:54 > 0:52:56'They were the first living things to use the process
0:52:56 > 0:52:59'we call photosynthesis.
0:52:59 > 0:53:02'That is, they used carbon dioxide, water and sunlight
0:53:02 > 0:53:05'to produce food to sustain themselves,
0:53:05 > 0:53:08'the same process plants still use today.
0:53:08 > 0:53:13'And, crucially, the waste product of that chemical reaction is oxygen.
0:53:17 > 0:53:22'The presence of this vital new element had a dramatic effect on the planet's oceans.'
0:53:25 > 0:53:28These early organisms, the cyanobacteria,
0:53:28 > 0:53:30were producing oxygen as waste,
0:53:30 > 0:53:33so suddenly there's oxygen creeping into the ocean environment.
0:53:33 > 0:53:34Where did it go?
0:53:34 > 0:53:39Initially, that would have been used up by all the free iron that was...
0:53:39 > 0:53:42or the dissolved iron that was in the ocean,
0:53:42 > 0:53:46to form iron oxides, which is a red mineral.
0:53:46 > 0:53:49And then you've got, basically, red dust raining out of the oceans
0:53:49 > 0:53:51and just falling to the ocean floor
0:53:51 > 0:53:53and building up over a very long period of time.
0:53:53 > 0:53:56Covering the oceans in a layer of red.
0:53:58 > 0:54:01'So, at first, oxygen combined with the dissolved
0:54:01 > 0:54:04'iron in the oceans to form solid iron oxide.
0:54:07 > 0:54:10'Eventually, when this iron had been used up,
0:54:10 > 0:54:14'oxygen continued to accumulate and made its way into our atmosphere...
0:54:20 > 0:54:23'..transforming it gradually into the air we breathe today,
0:54:23 > 0:54:25'essential for life as we know it.
0:54:27 > 0:54:31'And that oxygen also reacted with other elements in the environment.
0:54:31 > 0:54:33'changing the colour of our planet.'
0:54:34 > 0:54:37And once you've got free oxygen in the atmosphere,
0:54:37 > 0:54:40and that's part of what's generated the ochre around us here?
0:54:40 > 0:54:44Yes, iron will react with oxygen to form iron oxide,
0:54:44 > 0:54:47and that's what we see here in these caves.
0:54:47 > 0:54:51So these tiny organisms changed the colour of the planet?
0:54:51 > 0:54:53Yes.
0:55:03 > 0:55:06'Even though the combination of iron and oxygen
0:55:06 > 0:55:09'has painted swathes of our planet red,
0:55:09 > 0:55:11'it's created other colours. too.
0:55:17 > 0:55:20'Iron oxide can exist in various forms,
0:55:20 > 0:55:23'all of which have their own distinctive colour.'
0:55:30 > 0:55:34Ochre isn't just the red colours, the haematite.
0:55:34 > 0:55:35There's lots of others as well.
0:55:35 > 0:55:38Right here there's yellow, and there are also purples and browns,
0:55:38 > 0:55:43so just this one compound has a whole paint box associated with it.
0:55:46 > 0:55:50And it's a strange thought that 2.3 billion years ago
0:55:50 > 0:55:52in an ancient ocean,
0:55:52 > 0:55:55one of the simplest organisms we know of
0:55:55 > 0:55:58started producing a waste product, oxygen.
0:55:58 > 0:56:03And that heralded the first appearance of these colours.
0:56:03 > 0:56:05And then 2.3 billion years after that,
0:56:05 > 0:56:08one of the most complicated organisms we know of,
0:56:08 > 0:56:10a human being,
0:56:10 > 0:56:13walked up to a wall like this
0:56:13 > 0:56:16and did what comes naturally. They did this.
0:56:26 > 0:56:30'Ochre is so common and so colourful that it's been
0:56:30 > 0:56:33'used in art for more than 75,000 years...
0:56:35 > 0:56:40'..reflecting the importance our ancestors placed on the colour red.
0:56:45 > 0:56:49'It's found in prehistoric cave paintings across Europe,
0:56:49 > 0:56:51'the Americas and Australasia.
0:56:53 > 0:56:56'Even though these distant civilisations never met,
0:56:56 > 0:56:59'the content of their art is remarkably similar.
0:57:00 > 0:57:04'And their ubiquitous use of red symbolises the relationship
0:57:04 > 0:57:07'between them and the land from which they sourced this colour.'
0:57:19 > 0:57:24These are ancient colours, both for our planet and for our species,
0:57:24 > 0:57:27but what an accident of history these represent.
0:57:28 > 0:57:33A waste product, oxygen, seeped into the early Earth,
0:57:33 > 0:57:34ended an era,
0:57:34 > 0:57:36and began another.
0:57:36 > 0:57:39The raw mineral colours of Earth
0:57:39 > 0:57:42were about to become the background for a far richer palette
0:57:42 > 0:57:45because the arrival of oxygen made possible
0:57:45 > 0:57:46the arrival of complex life.
0:57:48 > 0:57:52This new palette would be driven by evolution
0:57:52 > 0:57:56and so these colours represent the transition of Earth
0:57:56 > 0:58:00from a hostile, young planet to something new.
0:58:00 > 0:58:01A home.
0:58:03 > 0:58:05'Next time, the colours of life.
0:58:07 > 0:58:08'I'll discover the bizarre
0:58:08 > 0:58:12'and beautiful ways that the living world has harnessed colour...
0:58:12 > 0:58:15The forest here is green and healthy.
0:58:15 > 0:58:20'..from basic survival to the strange and sophisticated.'
0:58:20 > 0:58:24Deep-down physiological changes, broadcast in colour.
0:58:26 > 0:58:29Discover more about the story of the colours of the Earth
0:58:29 > 0:58:31with The Open University.
0:58:31 > 0:58:34Go to...
0:58:34 > 0:58:37..and follow the links to The Open University.