"Whoo hoo!" "I'm here!" "This is it." "There's the top just there." "Ah, this is fantastic!" "What a view!" "I'm back." "I was last here 25 years ago." "25 years!" "And somewhere around here I left my hammer." "Ah, look at this!" "Here we are!" "Whoo!" "Would you look at this?" "Look at this view." "This is what I remember." "This is our ancient heritage laid out before our very eyes." "Scotland's landscape has an epic and violent past." "Hidden in these mountains and glens is the history of the planet." "I'm going to show you how this landscape was used by a bunch of brilliant, maverick, eccentric scientists to solve the greatest mysteries of the Earth." "I'm following in the footsteps of these pioneers who blazed a trail where no-one had been before." "They showed vision and determination... ..to piece together baffling evidence and uncover the forces that shape our world." "Wow!" "God, that's so hot!" "It's all out there if you know what to look for." "Written into the Scottish landscape is the story of the entire planet." "The remote northwest Highlands of Scotland." "If feels like the ends of the Earth." "For centuries, people have looked at this landscape and wondered how long it's been here and how it was formed." "It wasn't until the 1750s that the answer began to emerge, from myth and superstition towards a new view of the Earth based on science." "One man had a revolutionary new idea that changed everything - changed the way we thought about the planet, even about the way we thought about ourselves." "The man who started this scientific revolution grew up in Scotland's capital, Edinburgh." "James Hutton was to become the founding father of geology." "As a young man, the hills around his home city made him curious about how the Earth was formed." "Hutton used to come up here a lot." "He would have made a fantastic travelling companion." "He was funny, bawdy, a bit rude." "He liked his whisky, liked his women, and he loved debating new ideas." "In 1747, Hutton was a young medical graduate with an unusually broad interest in the whole natural world." "When he studied the origins of the landscape, he found that the accepted authority was not science but theology." "When Hutton started to think about the Earth, there really was only geology textbook available - the Bible." "What I love about this edition from Hutton's time is it gives a date for when God created the Earth and the seas." "Before Christ 4004." "Not just in 4004BC, but on Saturday the 22nd October, 4004BC." "Hutton believed in God." "But unusually for a man of his time, he was not committed to a literal interpretation of the Bible." "He believed that God had created a world that had a system of natural laws." "But he didn't particularly dwell on these ideas." "Instead, he did what many students do." "He got drunk." "He was also getting seriously distracted by the ladies and it was that that would prove his downfall." "It was Hutton's relationship with one particular woman that seems to have led to heartache and to his banishment from his beloved Edinburgh." "Hutton had got his young lover, Miss Edington, pregnant." "This was a scandal." "She was rushed away to London to give birth." "To limit the damage to his family's reputation, Hutton left Edinburgh." "At the age of 26, he was forced to make a new life on a small disused family farm in southern Scotland." "Hutton wrote that it was," ""A cursed country where everything conspires to break my heart."" "But it was this remote farm that would trigger his brilliant insights about the planet." "Well, this is Slighhouses Farm but... what a landscape!" "It's bleak and windswept and pretty soggy today." "Certainly not the kind of place where you feel that you would devise a major new theory about the Earth as a system." "But that is exactly what Hutton did." "First, he had to turn this rain-drenched landscape into a profitable working farm." "One of the dirty jobs he constantly faced was to dig and clear drainage ditches." "Hard work!" "'Denise Daly Walton farms nearby and knows what he was up against.'" "Well, the purpose of this ditch was to carry the water off the field but what's happened over time is that the sediment, all the topsoil, has run off the fields and has actually blocked this up." "This is gold dust in terms of cultivated land but it's wasted in these ditches." "Agh!" "Every year, Hutton cleared these drainage ditches." "And every year, the rain washed the precious topsoil off his fields into the ditches and carried it downstream." "This burn draining through Hutton's land was the start of a long journey for all that soil washed away from his fields." "The water flows down into larger and larger streams and rivers and of course where the water flows the sand silt and mud follows, eventually being dumped in the sea." "This incessant erosion of the land seriously concerned Hutton because he realised that if all the soil was washed away, then eventually there'd be nothing to grow crops in and ultimately people would starve." "Hutton looked at this erosion and realised it must happen not just in Scotland, but across the whole planet." "It appeared that God had made a world that stripped farms of good soil." "Eventually, if this continued, there would be an utterly barren landscape." "But to be honest, Hutton just didn't buy that." "In his heart, it made no sense that God would let his people starve." "And in his head, it made no sense that the Earth would irreversibly wear away to nothing." "He was convinced that there had to be a way to make new land." "Hutton still only 34 and working in isolation, had come to reject the conventional view of the Earth." "He couldn't accept that the world had been created by God at a single stroke and remained unchanged." "His radical thought was that God must have designed a planet that could rebuild itself." "The question was, how could new land be formed?" "Hutton spotted something in the landscape around his farm that gave him his first clue." "Hutton would have seen cliffs like this all over the place." "If you look at this rock face, you see distinct layers of rock, all of them subtly different." "Hundreds of them." "What Hutton realised was that these bands of sediment were laid down at different times." "Flushed in from rivers and deposited one on top of the other." "Just builds up over time, year after year, slowly compacting into rock." "Hutton's greatest idea - and I guess it seems so obvious now - is that the creation of land and the destruction of land are not sudden and dramatic events in the dim and biblical past, but slow and imperceptible actions that are going on all the time." "They're going on right now." "The idea that land was created from the rubble of the past was a startling new way to see the landscape." "And this sedimentary rock, formed from layers of mud and sand laid down on rivers and seas, is found everywhere." "From the white cliffs of England's south coast... to America's Grand Canyon." "Hutton had made his first breakthrough." "He was now sure there was a great system driving the Earth." "After 15 years on the farm, Hutton was about to start a new chapter in his life, one that would test his ideas and push him to even greater discoveries." "At the age of 41, his years of exile were over." "He returned to the city of his youth." "It was the time of the Scottish Enlightenment." "Edinburgh was the intellectual capital of the world." "Hutton made the most of being back." "All over town, he debates and drinks with the greatest minds of his era." "You can see why these gatherings were ideal for Hutton, his personality a mix of deep thinker and deep drinker." "This open convivial atmosphere was perfect for him to air his big idea." "Mind you, even all this bonhomie wasn't enough to paper over the cracks in Hutton's theory." "Hutton knew that not all the rocks he could see had been laid down in layers of sediment." "If the Earth's system continually recycled all land, what other ways could rocks be formed?" "Hutton still had a large piece of the jigsaw missing." "He got his inspiration from another great mind of the Scottish Enlightenment." "His friend - an arguably more famous James" " James Watt." "Fellow Scotsman James Watt was an accomplished inventor." "Famous for making steam engines more efficient." "It was James Watt's harnessing of heat that would power the Industrial Revolution." "Hutton had a thing about machines and he was fascinated by Watt's steam-powered contraptions." "Hutton saw that heat gave steam engines enormous power." "He began to wonder if heat powered the planet." "Maybe heat within the Earth was a force that could change and renew the landscape." "Perhaps the centre of the Earth contained a mighty heat engine." "Scientists in the 1700s had seen active volcanoes." "But they thought they were only small, isolated fires." "Hutton was the first person to imagine that the centre of the Earth was a molten ball." "He saw volcanoes as the vents of a giant furnace deep in the Earth." "He believed that this furnace had the power to create new land... land that was born molten." "If he could prove that much of the landscape had started out molten, then he would have discovered another way in which the Earth could continually renew itself." "The trouble was that if a lot of the rocks started off molten, why were they all so different?" "If they had the same origin, then surely they would look the same?" "If you were trying to define genius, then I guess it would be about making remarkable connections that no-one had ever considered before." "But time and time again, he got his ideas from farm ditches, from local cliffs and from steam engines." "And perhaps his cleverest piece of lateral thinking was when he hears of an accident in a glass bottle factory." "Next one..." "Glass artist Siobhan Healy is going to help me recreate the incident that caught Hutton's attention." "Something immensely satisfying about this!" "'At a glass factory in Edinburgh, 'the workers accidentally left a batch of molten glass 'in the kiln too long.'" "OK." "'We've got two piles of broken glass." "'We'll treat one normally and use the other to re-create the accident.'" "So this is ready." "I'll just close it over." "That's us up to our top temperature." "It'll go completely molten at that temperature, it goes like liquid." "So this one goes in the other one, the slow one?" "Yes, this one's going to be substantially longer, this programme, because everything will be exactly the same apart from the rate of cooling." "The reason Hutton was so interested in the results is because he knew that molten glass would behave in the same way as molten rock." "Wow!" "God, that's so hot." "So that is what 900 degrees feels like?" "That's fantastic." "Yeah." "Oh, that's so hot." "You just want to touch it " "I know it's the last thing my fingers would do, but..." "Oooh, scorchio." "Scorchio." "'We have cooled the two samples at different rates." "'The results are dramatic.'" "This one here is what?" "This is the vitrified piece of glass." "This is the one that cooled fast, quenched really fast." "Yes." "You can see right through it, it's beautifully transparent." "Look at that." "But this is completely different." "This is a molten rock that's solidified really slowly." "So you can actually see the crystals in here, little angular crystals, and the texture's completely different." "Crystals are formed inside the glass or rock when atoms stick together." "It takes a long time for clusters of atoms to grow big enough to be seen." "When glass cools quickly, the crystals are very small and the glass is clear." "But when the workers left the glass to cool down over a long period, large crystals were created." "Hutton had an explanation for the many different rock types we see on the earth's surface." "Very slow cooling creates large crystals." "Faster cooling creates smaller crystals, like in this granite." "And rapid cooling creates tiny crystals, like in volcanic basalt." "All we've done is alter how fast the molten glass cooled, and we've created two completely different materials from it." "Hutton grasped that a whole variety of rocks could have started off as molten and as they solidified under different conditions their appearance and look would change." "This meant that heat could have formed far more of the earth's surface than previously thought and it convinced Hutton that there really was a vast internal heat engine at work." "Hutton had come up with two fundamental ways that land could be created." "Sedimentary rock could form when weather - rain, frost, and wind - eroded the soil." "Rivers carried the sediment to the oceans." "It was compressed to form new rock." "And his second idea?" "That a hot core in the centre of the earth could create molten rock which cooled to become land." "He had a clear vision of an earth that destroyed and repaired itself in an endless cycle." "Hutton's idea is so, so beautiful." "And amazingly for something that was conceived nearly 250 years or so ago, it's nearly all right." "It's a big, coherent, impressive idea." "And this concept of the earth as a system, continually self renewing, well, it feels so modern." "But the big question was, back then, was the world ready for it?" "Hutton had to be persuaded by friends to go public with his ideas." "He was worried about how they would be received." "But in 1785, he presented his theory of the earth as a system at the Royal Society of Edinburgh." "Imagine the scene." "In front of some of the greatest scientists of the age, the outsider Hutton prepares to present his radical theory of the earth." "He's a terrible speaker, though, he talks in a broad Scots accent." "And he's incredibly nervous." "What's more, he's got this nagging feeling that he doesn't yet have enough evidence from the field to back up his theory." "And he knows that what he's going to say is really controversial." "His ideas go against all the religious orthodoxy of the day." "In the event, his worst fears are realised." "The presentation bombs." "The gentlemen of the Royal Society rejected Hutton's theory out of hand." "Worse for the God-fearing Hutton, he was accused of being an atheist." "One of the biggest upsets was about this stuff - granite." "It's hard to believe that this could cause even mild disagreement." "But it produced a most almighty stink." "The accepted wisdom was that granite was the first part of earth to be created by God." "Nothing could be more solid than the Lord's foundation stone." "Seems solid enough." "But Hutton was claiming that this hard stuff which seems so ancient and immutable was actually the prime example of a young rock which had once been almost liquid." "He was saying this was born molten." "To claim that granite had started out molten challenged the whole biblical view of creation." "220 years ago, this was heresy." "Hutton needed to find some evidence from the field." "At the age of 60, when he should have been at home with his pipe and slippers," "Hutton hit the trail." "He headed north east from Edinburgh into the wild hill country of Blair Atholl in Perthshire." "Travelling in the 1780s was a wee bit different to what it is today." "It's going to take me a couple of hours to go from Edinburgh to Blair Atholl in the South East Highlands, but for Hutton it would have taken three days on horseback." "His search for stones would routinely give him saddle sores." "He once wrote, "Lord pity the arse that's clagged..." That's "attached" " ""..to the head that hunts for stones."" "But despite a sore arse, it didn't put him off." "'On the 16th of September 1785," "'Hutton travelled along this track in Glen Tilt." "'Hamish Cruickshank is a gamekeeper on the Atholl Estate.'" "You got a hell of an office." "It's one of the best offices in the world." "It's fantastic." "147,000 acres of office." "So if I was coming up here in 1785, it wouldn't be much different, I guess?" "Not much different." "You would be wearing the same sort of equipment as I'm wearing now." "The tweeds - really only the design has changed over the years." "Think you've more camouflaged in the landscape than I am!" "Certainly looks like it!" "Don't think I could stalk up on some deer with this." "Hutton chose to explore Glen Tilt because two of Scotland's great rivers meet here." "The River Dee runs over a bedrock of pink granite." "The River Tay has a bedrock of grey sandstone." "Where the rivers met," "Hutton hoped the granite and sandstone would also meet." "The contact, the meeting place, is right down the river and that's what Hutton was going for." "And if he could find where the two rocks met, maybe he would find evidence that granite had flowed as a molten liquid into the sandstone." "As Hutton made his way along the river, he could see the grey sandstone frustratingly close to, but never quite touching, the pink granite." "Then Hutton arrived at these rapids." "This is the bit." "Look at this!" "Wonderful." "Hutton must have been just so pleased to see this." "You can see there the grey rock, that's the layered rock, and then in front of us here, this pinky rock, which is the granite." "And here, especially over on the other side, you can see it's all mixed in." "If you come and look, actually there, look down there, you see the pink rock and the grey rock is all muddled in." "And that's the bridge." "There used to be a bridge over here." "Now there's no easy way to get across." "Well, Hutton had saddle sores." "I think I'm going to have rope burns." "Woo-hoo!" "This is the rock Hutton was looking for." "There's a cracker over here." "Look at this." "This is the beautiful red granite and this is the grey layered rock, the sandstone." "You can see how the granite is injecting itself forcefully into the sandstone." "This is a brilliant bit." "Look at this." "It's just mad." "There's bits down here." "It's so irregular." "It's kind of like Italian ice-cream or something." "Lovely." "You know, it's crystal clear here that the granite came from molten rock." "It's getting injected in all directions." "It's this way, this way, over there it's going up there, it's across that way." "This is like a geological battle zone." "These rocks showed that the landscape had changed." "It had not, as the Bible said, remained unchanged since creation." "Molten granite was proof of a giant heat engine in action." "This discovery in Glen Tilt was a great moment for Hutton." "It's the kind of thrill that every geologist is after." "It's why I too am fascinated by the rocks all around us." "The core to being a geologist is this ability to read the landscape but it's really hard to explain to someone else." "You just get used to it." "It's kind of intuitive." "It's kind of like a curse as well because suddenly you can't really..." "I don't know, enjoy a landscape without thinking," ""What is that?" "How was it formed?" "Is that sandstone?"" "I always get told off when I'm on holiday for working when I'm looking at the landscape." "My wife says, "Stop geologising, stop working!"" "I say, "I'm just looking." But it's true." "I think a geologist can't look at what's around and not think, "How was that formed?"" "From his observations in Scotland," "James Hutton had proved much of his theory of the earth as a system." "Rocks were molten and cooled." "They were eroded and built up again." "Hutton was not yet satisfied, and he set off once more." "This time he was in search of clues as to how long this planet cycle of renewal had been going on for." "Was the earth thousands of years old, as the Bible said, or was it much, much older?" "In 1788, Hutton headed to Siccar Point on the Berwickshire coast, just a few miles from his old farm." "This time in April, normally, the seas round here can be treacherous, but we've got a beautiful calm sunny day, which is pretty much the weather Hutton had when he came here by boat with two friends to try and convince them about his theories of the earth." "What Hutton was on the lookout for turned out to be the most celebrated geological find in history." "Hutton knew this coast well." "What intrigued him was the different angles of the rocks along the cliffs." "He had seen vertical layers along part of the coast... ..but he knew that further north, the angle changed completely - the layers were horizontal." "'Hutton's curiosity made him take a closer look.'" "Cheers." "It's so good to be here." "I mean, I guess..." "I guess it looks like a pretty normal piece of rocky foreshore to most people, but this place is geological gold." "I mean, quite simply, this is the most important geological site on the planet." "You'd never know it to look at it, but there's a huge story to be told here - an epic tale of geological violence." "It takes you a while to see it, to get your eye in, but Hutton, Hutton knew instantly what he'd seen." "Nothing less than the birth and death of whole worlds." "What's remarkable is that Hutton could see all of this not in a giant cliff but a five-foot-high section of rock." "In these horizontal and vertical layers of rock, he saw one long geological cycle piled on top of another." "These layers of vertical grey rock started off as slurries of sand and mud sloped off an ancient landmass and deposited in the ocean." "They built up on the sea bed as horizontal sheets inch by inch over millions of years." "But although they started off horizontal, all that was about to change, because the ocean started to close." "What Hutton couldn't have known, but we've since discovered, is that continents move slowly across the globe, and this is why the rock layers are vertical and don't lie flat." "Over millions of years, a continent slowly and relentlessly drifted towards Scotland." "The sea-bed crumpled, pushing the layers of bedrock upright, higher and higher, until they became hills and mountains." "And there, erosion started again, rivers and rain wearing down the land." "On top of the upright grey layers, fresh sediment gradually built up and solidified into new flat layers of rock." "Hutton didn't know exactly what caused the formation at Siccar Point." "His brilliant insight was to realise it must involve gradual processes that happened not in biblical time but in deep time, stretching back immeasurably." "Hutton was right and we now know how old these layers of rock are." "This grey rock is around 425 million years old and this red rock is about 345 million years old." "The gap between the two is 80 million years." "And that is ultimately Hutton's most important legacy - an appreciation of deep time..." "..the timeline of a planet." "Hutton had a phrase that he used, he said, "No vestige of a beginning, no prospect of an end."" "In other words, a timelessness in which small gradual changes can achieve almost anything." "Here at Siccar Point, James Hutton realised that if one ancient rock formation could sit on top of another, this process must have taken an inconceivable length of time." "He had no idea of how long." "Indeed, he never offered an exact timescale." "He could only imagine the cycle of the Earth had gone on endlessly." "Hutton's recognition of Deep Time was an extraordinary breakthrough, every bit as significant in its way as Darwin's theory of evolution or Einstein's theory of relativity." "As with all these great scientific advances it was difficult for people to believe." "Ideas in geology..." "Well, in science for that matter, are kind of like a relay race where the baton gets passed from hand to hand." "Hopefully each time the baton gets passed along, the ideas get more solid and more accepted." "But in the case of Hutton, that baton got seriously dropped along the way." "60 years after Hutton's death, Britain's most respected physicist tried to calculate the age of the Earth." "A Scottish scientist so successful he could afford a luxury yacht like this." "Its time to introduce you to a very different kind of scientist." "William Thomson - better known as Baron Kelvin of Largs." "He was a colossus of world science." "He's best known for the temperature scale." ""Degrees Kelvin," - that's him." "He was everything that Hutton wasn't." "He was deeply embedded in the academic establishment." "He was forceful, articulate, a real showman." "Kelvin was a brilliant scientist supremely confident in his own ability." "He rejected Hutton's theory of the Earth as a system of endless change." "The Earth had to have an age, even if it was far older than the Bible said." "Kelvin thought that Hutton and his followers were unscientific." "His main problem was the claim that the Earth showed" ""no vestige of a beginning, no prospect of an end,"" "and that it was in a kind of perpetual motion." "In other words he thought that geologists were trying to break the laws of physics." "It was time to smash that idea to pieces." "Kelvin was a showman." "And he had a dramatic way to show that the Earth must be losing energy all the time." "That could have been my head." "Here we have our 15 kilogram cannonball." "15 kilos I can hardly hold it." "It's a lot heavier than it looks." "All right, so what do we do?" "So I want you to stand in position and we'll bring the cannonball up." "'Dr Stuart Reid from Glasgow University 'shows me why Kelvin was convinced that Hutton's theory 'of endless change in the Earth was wrong.'" "Just hold it with your hands." "'This canon ball is a pendulum.'" "So heavy it's pulling me forward, it's such a weight." "Bring it right up to your nose." "Right here we go." "'When I let the pendulum go, it'll swing back towards me." "'If it hits me, my head will end up like the melon.'" "OK, here we go." "Why exactly is this not braining me then?" "It's not possible for the cannonball to end up swinging higher than where you let go of it, because it can't gain energy from nowhere and in actual fact it's losing energy because of friction in the rope cos of the air resistance as it's moving back and forth" "So the amplitude is decreasing as it's swinging and you can see that." "'For Kelvin this demonstrated that the planet, just like the pendulum, 'must lose energy all the time." "The Earth could not be 'in a cycle of change that would never slow and never stop.'" "You know it's a simple but effective demonstration of the real problem that Kelvin had with Hutton's theory the perverse notion that the Earth was constantly creating destroying then recreating its surface over and over again forever." "In fact the Earth should be constantly losing energy, just like this pendulum will eventually come to a halt... eventually." "Based on the principle that everything has to start and stop," "Kelvin was sure that the Earth had a beginning - an age." "Hutton was a bit, well, woolly, he never gave a precise age for the Earth." "Kelvin wasn't going to let him get away with that." "Grand claims needed to be backed up by hard figures and he, Lord Kelvin, was the man to get them." "He was going to take on the most audacious and controversial question of the era." "Lord Kelvin was going to calculate the age of Planet Earth." "This is a lump of granite... and we're gonna try and melt it." "Now, granite melts about 1,200 degrees Celsius several tens of kilometres buried beneath our feet." "We're going to try and melt it here with a blow torch." "Take it away." "Meanwhile I'm going to film it with a thermal infrared camera which is going to try and capture the heat and already I can see it soaring up." "It's 280, 300 degrees Celsius." "Whoa, it's bright, that's for sure!" "Kelvin believed the Earth started off molten." "Now it's hard to look at." "That's 1,000." "We're at 1,000 degrees Celsius." "The melting point of rock was Kelvin's start point to calculate the age of the Earth." "He took this as the temperature of the planet when it was created." "And there it is - 1,200 degrees Celsius!" "HE CHUCKLES Oh, yeah, look at that!" "This is molten rock!" "Beautiful!" "Kelvin argued that the planet couldn't stay molten forever." "Can we stop a second?" "This is now just basic physics." "Once something's heated up it can't stay hot - it has to cool down." "From his experiments Kelvin knew how long it took small objects to cool down." "If he scaled up his figures to calculate how long it would take an object the size of the planet to cool down, then he would have the exact age of the Earth." "For years, Kelvin continued to tweak and refine his calculations." "He finally put the age of the Earth at between 20 and 40 million years." "Although we now know the calculations aren't accurate," "Lord Kelvin's figures had an enormous impact." "He provoked intense debate about the age of the Earth and upset nearly everyone." "This is Kelvin." "Most times I've seen this statue, he's had a traffic cone on his head." "And he was ridiculed too when he published his age of the Earth." "The Church hated it because it made the Earth too old." "Fellow scientists they hated it because it made the Earth too young." "There just wasn't enough time for Darwin's theory of evolution to happen." "And as for Hutton's heat engine, well, on Kelvin's timescale, that was a non-starter." "Lord Kelvin had made a crucial error." "His calculation was based on the idea that the Earth had cooled to a completely solid state." "But as we now know the Earth's interior didn't just cool like a lump of molten rock." "Parts of it stay molten, just as Hutton imagined but couldn't prove." "Kelvin might have been wrong but his age of the Earth stood for almost 50 years." "Right up until 1898 when the rocks themselves revealed the truth." "A few years before Kelvin died, there was a major breakthrough." "Scientists discovered a source of energy deep within the planet that has helped keep the Earth molten far longer than Kelvin could have imagined." "Radioactivity." "MACHINE BEEPS" "This is a pretty ordinary lump of granite from the Scottish Highlands." "MACHINE CRACKLES" "And those clicks you're hearing are particles that are hitting the thin sheet at the front of this Geiger counter." "They're coming from a tiny amount of radioactive uranium contained in the rock." "MACHINE CRACKLES" "We tend to think of radioactivity as man-made but it's actually a natural phenomenon." "A powerful energy source that's been around since the birth of the Solar System." "Radioactivity is one of the key forces that makes Hutton's theory correct." "I'd love to meet Hutton and, over a whisky and beside a warm fire, tell him about all the things we've discovered since he's been gone." "Top of that list would be radioactivity." "The energy of radioactivity and the heat that it generated has kept parts of the planet's interior molten." "It's part of Hutton's heat engine which has allowed the Earth's surface to be constantly recycled and rejuvenated." "But there's another reason why I'd love to tell him about radioactivity, and that's because as well as explaining his heat engine, it's been responsible for telling us just how old the planet is." "We can now look at the most ancient rocks on our planet and discover their true age." "I've returned to Torridon, in the North West Highlands." "I'm hoping to find the oldest rocks in Britain up here." "I want to find out just how old Scotland is." "And radioactivity will give me the answer." "I'm heading into the back country with fellow geologists John Wheeler and Ian Miller." "You can see it's kind of swirly, can't you?" "Oh, yeah." "'This hill is 50 times older than the era of the dinosaurs." "'It is one of the earliest parts of our planet.'" "Wow, this is spectacular, isn't it?" "Look at this!" "This whole outcrop is just...kind of vein after vein after vein of this beautiful white rock." "This rock is called Lewissian Gneiss." "This is kind of rock heaven for me." "It's just the textures, the shapes the colours of this Lewisian Gneiss - it's beautiful, gorgeous." "And here this stuff's coming across and it stops." "But what's even more fascinating, more mind-blowing than how gorgeous it is, is that this rock could be part of the very first bedrock of Britain." "Here we go." "This is the dark side of geology." "It's cold, hard work." "Yes!" "'Much as I love this rock, we need to take a sample so we can measure its age.'" "OK, that's pretty good." "Is it?" "It's getting nasty now the snow's really coming in but we've got it." "We've got the rock we wanted." "It's a beautiful piece of Lewissian Gneiss." "And apart from just looking gorgeous, this is the question - am I holding in my hand a fragment of one of the oldest bits of Britain?" "We're going to find out but we've got to get it to the lab." "Let's get off this mountain." "So this is it, this is my rock." "Here it is." "The plan now is to find out how old this piece of Scotland is." "The key thing that we have to do first off, is we have to smash the hell out of this rock and we do this in this machine here." "LOUD CLATTERING" "'The ground-up rock contains the radioactive crystals I need.'" "Ha!" "Look at it." "So that's what our rock started like and that's what it is now." "Somewhere in here are the little crystals we want today." "'Now we're going to examine those crucial crystals using an electron microscope.'" "That creates a vacuum?" "That's creating a vacuum inside." "From your sample that you collected, we've managed to extract a large number of zircon crystals." "'The zircon crystals are time capsules." "'They're full of radioactive uranium, which breaks down into lead 'at a regular rate.'" "You can actually see the shape of the crystals quite nicely." "Absolutely, yeah." "That's really beautiful." "'The proportion of uranium and lead left in the zircons will reveal the age of the rock.'" "'The machine spits out an extraordinary bunch of numbers.'" "Lots of numbers." "Lots and lots of numbers." "My gosh, lots of numbers." "Many many numbers." "They're ranging from about 2,500, up to a little bit over 300 million years old." "These ages are just unfeasibly old." "I mean, 3,129 million years." "It is astonishingly old." "It's amazing." "You know the fact that it's between 2.6 and three billion years old is truly remarkable." "I mean this thing has been around for two-thirds of the age of the planet." "The Earth is 4.6 billion years old." "And the notion that a lump of Scotland is almost 3,000 million years old?" "Well, what would Hutton have made of that?" "The rocks of Torridon were created when the very first continents on Earth were being born." "The ancient landscape of Scotland is a witness to billions of years of geological change." "It was one pioneer who made this vision of our landscape possible." "James Hutton made one of the greatest leaps in human thought." "When he looked at the landscape he saw what no-one else had seen before." "He was the first to grasp the true, vast age of the Earth." "And it was that discovery more than any other that's allowed us to piece together the complex story of the life of our planet." "'Next time:" "I'll follow in the footsteps of the gung-ho geologist 'who uncovered Scotland's volcanic past." "'And the unsung hero...'" "You can actually see it starting to go up there." "'..who solved the mystery of what makes continents move across the surface of the globe.'" "Subtitles by Red Bee Media Ltd" "E-mail subtitling@bbc.co.uk"