0:00:05 > 0:00:09Everything around us exists somewhere on a vast scale,
0:00:09 > 0:00:12from cold to hot.
0:00:13 > 0:00:17The tiniest insects, all of us, the Earth, the stars,
0:00:17 > 0:00:21even the universe itself, everything has a temperature.
0:00:25 > 0:00:27I'm Dr Helen Czerski.
0:00:27 > 0:00:31In this series, I'm going to unlock temperature's deepest mysteries.
0:00:34 > 0:00:35Across three programmes,
0:00:35 > 0:00:39I'm going to explore the extremes of the temperature scale...
0:00:41 > 0:00:46..from some of the coldest temperatures to the very hottest,
0:00:46 > 0:00:49and everything in between.
0:00:49 > 0:00:53I'm a physicist, so my treasure map is woven from the fundamental
0:00:53 > 0:00:55physical laws of the universe,
0:00:55 > 0:00:57and temperature is an essential part of that.
0:00:58 > 0:01:01It's the hidden energy contained within matter.
0:01:03 > 0:01:08And the way that energy endlessly shifts and flows
0:01:08 > 0:01:11is the architect that has shaped our planet.
0:01:13 > 0:01:15And the universe.
0:01:16 > 0:01:19It's not often that I get up at 5am to watch a pond,
0:01:19 > 0:01:21but this one's worth watching.
0:01:24 > 0:01:29In this programme, I'll be exploring the incredible science of heat.
0:01:30 > 0:01:33What temperatures does it reach on the inside there?
0:01:33 > 0:01:36- 100 million degrees. - That's just a ludicrous number!
0:01:38 > 0:01:43I'll reveal how our ability to harness heat lies behind some of
0:01:43 > 0:01:46humanity's greatest achievements,
0:01:46 > 0:01:48from the molten metals that gave us tools...
0:01:52 > 0:01:56..to the searing energy of plasmas
0:01:56 > 0:02:00that offer the promise of almost unlimited power.
0:02:02 > 0:02:06Temperature is in every single story that nature has to tell, and in this
0:02:06 > 0:02:10series, I'll be exploring why, what temperature means,
0:02:10 > 0:02:13how it works, and just how deep its influence
0:02:13 > 0:02:15on our lives and our world really is.
0:02:47 > 0:02:51I love steam engines because they're so raw.
0:02:51 > 0:02:55You can see where the energy's coming from and where it's going to.
0:02:55 > 0:02:59This one's called Braveheart. It was built in 1951
0:02:59 > 0:03:01and still going strong.
0:03:01 > 0:03:03The steam out there is amazing!
0:03:04 > 0:03:08WHISTLE BLOWS
0:03:14 > 0:03:19Steam locomotives like Braveheart are a symbol of an age
0:03:19 > 0:03:23when it seemed that our ability to harness heat knew no bounds...
0:03:27 > 0:03:31..allowing us to drive our trains, run our factories,
0:03:31 > 0:03:34and propel our ships.
0:03:34 > 0:03:37The age of steam was about building machines to get stuff done,
0:03:37 > 0:03:42but to get the engineering right, people had to ask previously
0:03:42 > 0:03:45unanswered questions about what heat really was.
0:03:48 > 0:03:52And with the answers came an understanding of just how much heat
0:03:52 > 0:03:53could do for us.
0:03:56 > 0:03:59We're going past the modern world and the houses and computers and
0:03:59 > 0:04:01technology that we take for granted,
0:04:01 > 0:04:03all of which require a control of heat.
0:04:03 > 0:04:07All of that is built on the foundation of the Industrial
0:04:07 > 0:04:09Revolution, things like this engine.
0:04:11 > 0:04:16Right at the heart of the engine is the rawest bit and the first form
0:04:16 > 0:04:20of heat humans learned to control, and that is fire.
0:04:40 > 0:04:44In all of human history, there can be few moments more
0:04:44 > 0:04:47significant than the discovery of fire.
0:04:56 > 0:04:58The spark is so brief,
0:04:58 > 0:05:03such a tiny flash of light, and yet the start of such a huge story.
0:05:04 > 0:05:08A long time ago, perhaps around a million years, our ancestors
0:05:08 > 0:05:13could sit around a fire for the first time when they chose.
0:05:13 > 0:05:17And I'm sure that fire was just as mesmerising for them as it is for
0:05:17 > 0:05:20us, this flood of heat and light conjured up at will.
0:05:21 > 0:05:25You don't need any understanding of physics to appreciate this,
0:05:25 > 0:05:27or to be fascinated by it.
0:05:29 > 0:05:34It must have seemed amazing that something as apparently dead
0:05:34 > 0:05:37and inert as wood could suddenly change into flame,
0:05:37 > 0:05:40releasing so much heat.
0:05:42 > 0:05:44Our ancestors couldn't have known it,
0:05:44 > 0:05:48but mastering that spark opened the door
0:05:48 > 0:05:50to a whole new way of being human.
0:05:54 > 0:06:00The ability to create fire provided our ancestors with warmth,
0:06:00 > 0:06:03protection, and a means of cooking food.
0:06:05 > 0:06:07But for all the usefulness of fire,
0:06:07 > 0:06:12unlocking its full potential was still a long way off.
0:06:12 > 0:06:17For almost all of human history, we had no idea what heat could do
0:06:17 > 0:06:20for us because we just didn't know what it really was.
0:06:24 > 0:06:28It wasn't that long ago that people thought heat was a substance
0:06:28 > 0:06:29in its own right.
0:06:30 > 0:06:33A weightless fluid called caloric
0:06:33 > 0:06:37that could flow in and out of solids and liquids,
0:06:37 > 0:06:39altering their temperature.
0:06:41 > 0:06:46Not until the early 20th century did we discover that heat isn't
0:06:46 > 0:06:49a substance, but something else entirely.
0:06:54 > 0:06:57To show you,
0:06:57 > 0:06:59I'm going to heat up my favourite snack.
0:07:00 > 0:07:03What I've got here are popcorn kernels.
0:07:03 > 0:07:06And each one is the seed of a plant.
0:07:06 > 0:07:09But inside them, they've got a little bit of water.
0:07:09 > 0:07:13What's happening is that energy is flowing into the kernels.
0:07:13 > 0:07:16And the water molecules, as they heat up,
0:07:16 > 0:07:18are moving faster and faster.
0:07:22 > 0:07:24That water, the liquid water,
0:07:24 > 0:07:28is being pulled apart and so the liquid is becoming a gas
0:07:28 > 0:07:31and the popcorn kernels are filling up with steam.
0:07:31 > 0:07:36Every single one of these kernels is now a very small pressure cooker.
0:07:36 > 0:07:38And eventually...
0:07:38 > 0:07:40POPPING
0:07:40 > 0:07:42Ooh!
0:07:44 > 0:07:49And the pressure bursts the kernel out of shell.
0:07:49 > 0:07:52The whole kernel turns inside out, and then you get popcorn.
0:07:52 > 0:07:54That is flying everywhere!
0:07:57 > 0:07:59And the important point here
0:07:59 > 0:08:01is that the heat energy is all about movement.
0:08:06 > 0:08:10As atoms and molecules take energy on board, they start to speed up.
0:08:13 > 0:08:17The faster the movement, the hotter the substance is.
0:08:20 > 0:08:25And the crucial point about all this movement or energy
0:08:25 > 0:08:29is its extraordinary ability to transform things.
0:08:32 > 0:08:34Even matter itself.
0:08:40 > 0:08:42I've come to Alderley Edge in Cheshire.
0:08:42 > 0:08:45- This goes around your back...- So this is just going round there.
0:08:45 > 0:08:48- That's right.- ..to see some early evidence of how we learnt to take
0:08:48 > 0:08:51advantage of this hidden ability of heat.
0:08:55 > 0:08:58Dating back some 4,000 years,
0:08:58 > 0:09:02the Alderley Edge mines are some of the oldest in Britain.
0:09:04 > 0:09:07Mind the steps. It's a bit slippery in places.
0:09:07 > 0:09:10Nigel Dibben from the Derbyshire Caving Club
0:09:10 > 0:09:12has offered to take me inside.
0:09:13 > 0:09:16Is your light on? There's mine on.
0:09:17 > 0:09:19Follow me in.
0:09:23 > 0:09:25Just mind your head here. It gets a bit low.
0:09:25 > 0:09:28- So this is all man made? - This is all man made.
0:09:30 > 0:09:33You can see some of these pick marks on the wall along here.
0:09:42 > 0:09:44I tell you what,
0:09:44 > 0:09:47this is not the easiest commute for anyone coming to work down here.
0:09:47 > 0:09:50Whatever's down the other end must have been pretty valuable.
0:09:55 > 0:10:00After a few more minutes, we come to the heart of the mine.
0:10:00 > 0:10:03This is what I really want you to have a look at.
0:10:03 > 0:10:05That's spectacular!
0:10:05 > 0:10:07That is a fabulous colour, isn't it?
0:10:07 > 0:10:10It's such an unexpected colour to find in the gloom, isn't it?
0:10:10 > 0:10:13And have a look down here as well.
0:10:13 > 0:10:16There's a bit more down the bottom, this shaft here.
0:10:16 > 0:10:19- Oh, yeah, a huge, great big stripe of it.- Down the bottom there.
0:10:24 > 0:10:28This mineral is chrysocolla, and it's dissolved into water
0:10:28 > 0:10:31that's dripping through the rock here, and then it's been redeposited
0:10:31 > 0:10:32in this beautiful sheet.
0:10:32 > 0:10:35And the spectacular colour is a hint
0:10:35 > 0:10:38as to why those early miners came down here.
0:10:38 > 0:10:43The pure version of the mineral that the miners were after is this.
0:10:44 > 0:10:46And this is malachite.
0:10:47 > 0:10:50When I was a kid, I was fascinated by semi-precious gems,
0:10:50 > 0:10:53and it was malachite that got me started on that.
0:10:53 > 0:10:54I couldn't leave it alone.
0:10:54 > 0:10:58It's a beautiful, deep, rich, green colour.
0:10:58 > 0:10:59And it's not just me - it's been
0:10:59 > 0:11:02used by humans for millennia as a green
0:11:02 > 0:11:04pigment because of the way it looks.
0:11:06 > 0:11:09But malachite doesn't just have style, it has substance.
0:11:12 > 0:11:15Because when you take malachite and heat it up,
0:11:15 > 0:11:17you start to transform it.
0:11:19 > 0:11:21Malachite is a mineral,
0:11:21 > 0:11:24which means it's made of lots of different types of atoms,
0:11:24 > 0:11:27all bound up together, but you can't see what's in there.
0:11:27 > 0:11:31But once you heat it up, you can drive off the smaller atoms,
0:11:31 > 0:11:33the carbon and then the oxygen,
0:11:33 > 0:11:36and then what you have left is the element that's at the heart of this,
0:11:36 > 0:11:38which is this.
0:11:38 > 0:11:42It's copper, the first metal to be smelted from its ore.
0:11:42 > 0:11:45Copper is strong and malleable and shiny.
0:11:45 > 0:11:48It's completely different from the mineral it came from.
0:11:48 > 0:11:52And the clear implication is that heat can change things.
0:11:52 > 0:11:55And so it wasn't far to the next step of the imagination.
0:11:55 > 0:11:59Because if heat can change this into this, what else can it do?
0:12:02 > 0:12:07The answer came when people realised that just as heat can turn rock into
0:12:07 > 0:12:10metal, so with a little know-how
0:12:10 > 0:12:14it could also be used to alter the metal itself.
0:12:22 > 0:12:27In the year 793, Anglo-Saxon Britain came under attack...
0:12:33 > 0:12:37..when Viking raiders first landed on the Northumbrian coast.
0:12:43 > 0:12:47While the Vikings' reputation as fearsome warriors is
0:12:47 > 0:12:51well-documented, what's less well-known is their skilful
0:12:51 > 0:12:55craft work, especially with metals.
0:12:58 > 0:13:04A skill calling not only for a sense of design, but also a sophisticated
0:13:04 > 0:13:06understanding of temperature.
0:13:15 > 0:13:20To find out more, I've come to meet historical blacksmith Jason Green.
0:13:25 > 0:13:29- And how hot will it get in there? - Around 1,300 degrees.
0:13:29 > 0:13:34Under Jason's watchful eye, I'm going to attempt to make a Viking
0:13:34 > 0:13:39dagger, a process that starts with heating up a small piece of steel,
0:13:39 > 0:13:41before hammering it into shape.
0:13:44 > 0:13:47- That's it.- OK.
0:13:47 > 0:13:48Not setting the grass on fire.
0:13:48 > 0:13:51- The only way you're going to learn is to do it.- By doing it.
0:13:51 > 0:13:54Right, well, there is going to be a lot of doing, isn't there?
0:13:59 > 0:14:02You can feel as it cools, it suddenly stops going anywhere!
0:14:02 > 0:14:04- Yeah, it starts getting harder. - Yeah.
0:14:05 > 0:14:08Blow by blow, my dagger starts to take shape.
0:14:09 > 0:14:15Both externally and, more importantly, deep inside the metal.
0:14:17 > 0:14:19We don't tend to think of metals
0:14:19 > 0:14:22as being crystals, but in fact they are.
0:14:25 > 0:14:28That means their atoms are arranged
0:14:28 > 0:14:30into a highly regular, repeating pattern.
0:14:34 > 0:14:38What's happening as we heat is that the crystals are changing because
0:14:38 > 0:14:41the heat makes them slightly more mobile,
0:14:41 > 0:14:44it allows you to push atoms around.
0:14:45 > 0:14:50As I hammer away, each impact rearranges the atoms inside...
0:14:52 > 0:14:56..creating tiny knots within the crystalline structure.
0:14:58 > 0:15:00As these knots accumulate,
0:15:00 > 0:15:04it becomes harder for the atoms to move over each other.
0:15:06 > 0:15:09And this helps make the metal stronger.
0:15:12 > 0:15:16And so all of this raw action,
0:15:16 > 0:15:19this hammering, thumping, and the heating,
0:15:19 > 0:15:23is changing things at a very tiny scale inside the metal itself.
0:15:23 > 0:15:25And that's what gives iron and steel
0:15:25 > 0:15:28its strength and that's why it's so useful.
0:15:28 > 0:15:31But a blade's strength doesn't come from hammering alone.
0:15:34 > 0:15:39It also requires clever manipulation of its temperature.
0:15:39 > 0:15:42The knife's now back in the forge, glowing cherry red,
0:15:42 > 0:15:44and that means it's about 800 degrees C.
0:15:44 > 0:15:48And that matters because the crystal structure at this temperature,
0:15:48 > 0:15:51this is the one we want. It's very strong, it's really useful.
0:15:51 > 0:15:53If I let it cool down slowly,
0:15:53 > 0:15:56it will change back to the room temperature structure.
0:15:57 > 0:16:01And so in order to keep this crystal structure, so it's a useful knife,
0:16:01 > 0:16:03this is what we do...
0:16:04 > 0:16:06..which is very satisfying!
0:16:14 > 0:16:17As the hot metal is plunged into the water,
0:16:17 > 0:16:20its temperature plummets in just a few seconds.
0:16:23 > 0:16:25By cooling it so quickly,
0:16:25 > 0:16:28the atoms haven't got time to shift into the shape that they want to
0:16:28 > 0:16:32have, and so they're stuck, locked in with a very strong structure.
0:16:34 > 0:16:40Finally, one last round of heating to remove any remaining brittleness.
0:16:43 > 0:16:46There we go. One finished fighting blade.
0:16:46 > 0:16:48I'm so impressed that with such simple tools
0:16:48 > 0:16:50you can make something so useful.
0:16:50 > 0:16:53That's brilliant. Thank you very much.
0:16:58 > 0:17:02By turning wood into flames,
0:17:02 > 0:17:06rock into metal,
0:17:06 > 0:17:09and soft metal into hard,
0:17:09 > 0:17:14our ancestors' growing understanding that heat could transform matter
0:17:14 > 0:17:17altered the course of human civilisation.
0:17:22 > 0:17:23But for thousands of years,
0:17:23 > 0:17:26this knowledge was only applied to solids.
0:17:29 > 0:17:33The next leap forward would see people using heat to exploit another
0:17:33 > 0:17:37form of matter, one with astonishing potential.
0:17:40 > 0:17:41Gas.
0:17:44 > 0:17:47But to understand how gases respond to heat,
0:17:47 > 0:17:52we first need to take a step back and look at what gases are
0:17:52 > 0:17:54and how they behave.
0:18:03 > 0:18:05Humans love a bit of spectacle,
0:18:05 > 0:18:08anything with colour and music and fun.
0:18:08 > 0:18:11But the stereotype of a scientific experiment is almost exactly the
0:18:11 > 0:18:15opposite, a dusty basement with someone who hasn't seen daylight for
0:18:15 > 0:18:18a week, writing down measurements that no one will ever read.
0:18:21 > 0:18:24But there have been exceptions. There have been experiments
0:18:24 > 0:18:29set up with the theatrical drama to match their scientific significance.
0:18:29 > 0:18:33And one of my favourites happened in 1654, and it was all organised
0:18:33 > 0:18:35by a man called Otto von Guericke.
0:18:38 > 0:18:42The aim of the experiment was to demonstrate a very specific and
0:18:42 > 0:18:45extraordinary property of gases.
0:18:48 > 0:18:51And heading up the guest list was none other than the Holy
0:18:51 > 0:18:54Roman Emperor, Ferdinand III.
0:18:57 > 0:18:59When the Emperor and his guests were all seated,
0:18:59 > 0:19:03it was time for the star of the show, and that was two metal
0:19:03 > 0:19:06hemispheres like these, with flat inner surfaces.
0:19:06 > 0:19:09Von Guericke placed the two hemispheres together and then
0:19:09 > 0:19:12started to take out the air from the inside.
0:19:14 > 0:19:18This created a vacuum which held the two halves of the sphere together.
0:19:21 > 0:19:22And it was what Von Guericke
0:19:22 > 0:19:24did next that made everyone pay attention.
0:19:27 > 0:19:30He set up a team of horses on either side...
0:19:32 > 0:19:34..put the sphere in between,
0:19:34 > 0:19:36and gave the command for the horses to pull.
0:19:41 > 0:19:43To show you what happened next,
0:19:43 > 0:19:47we're going to attach our sphere to the modern equivalent
0:19:47 > 0:19:51of Von Guericke's horses - a pair of 4X4s.
0:19:54 > 0:19:56Stand by.
0:19:57 > 0:19:59I'm actually quite nervous.
0:19:59 > 0:20:02Three, two, one.
0:20:02 > 0:20:03Go!
0:20:07 > 0:20:09So the tension's out of the rope.
0:20:12 > 0:20:15So now a little bit on the accelerator, just up to 1,000.
0:20:18 > 0:20:19Feel it taking the strain.
0:20:23 > 0:20:26OK. Keep going up to 1,300.
0:20:35 > 0:20:37Can feel it in the car.
0:20:37 > 0:20:39OK, up to 1,600.
0:20:41 > 0:20:43The engine is not happy!
0:20:48 > 0:20:51I think we might have established the sphere really works.
0:20:51 > 0:20:53OK, let's pause there, so stop.
0:20:56 > 0:20:58It's impressive. It really is impressive.
0:21:02 > 0:21:06Just as our sphere stood up to a pair of 4X4s,
0:21:06 > 0:21:08so Von Guericke's was also able
0:21:08 > 0:21:12to resist the pull of two sets of horses.
0:21:16 > 0:21:20To Von Guericke, it was the proof of something he'd long suspected,
0:21:20 > 0:21:25that gases like air exert an incredibly strong force.
0:21:33 > 0:21:37All the air around me looks completely calm, but it isn't.
0:21:37 > 0:21:41It's a gigantic, three-dimensional game of molecular bumper cars.
0:21:41 > 0:21:44Even in one cubic centimetre of air,
0:21:44 > 0:21:49there are nearly 30 million trillion air molecules and they're bumping
0:21:49 > 0:21:50into each other all the time.
0:21:50 > 0:21:56Just one molecule will collide several billion times every second.
0:21:56 > 0:21:59And every single collision gives a little bit of a push, and so if they
0:21:59 > 0:22:03bump into us, they push, and that's what air pressure is.
0:22:03 > 0:22:04And the question then is -
0:22:04 > 0:22:07if I'm being pushed on by this pressure all the time,
0:22:07 > 0:22:09why aren't I being squeezed?
0:22:11 > 0:22:14And the answer is that every time I breathe in,
0:22:14 > 0:22:16I'm taking air molecules into my lungs.
0:22:16 > 0:22:20And they're pushing out on the walls of my lungs and because the
0:22:20 > 0:22:24inward push and the outward push exactly balance, I don't notice.
0:22:28 > 0:22:31And that was why Von Guericke needed to generate a vacuum.
0:22:31 > 0:22:35You can only see how strong air pressure really is when you take
0:22:35 > 0:22:39away the push from the other side. At the end of the demonstration,
0:22:39 > 0:22:44all they needed to do was let a little bit of air back in and it was
0:22:44 > 0:22:46almost as though the pressure hadn't been there.
0:22:56 > 0:23:01The ability of molecules to exert pressure is one of the most
0:23:01 > 0:23:04fundamental properties of not just air, but all gases.
0:23:09 > 0:23:13But Von Guericke's discovery also raised an important question.
0:23:15 > 0:23:19If cold air molecules could have such a powerful effect,
0:23:19 > 0:23:24what might be achieved if those same molecules were heated up?
0:23:36 > 0:23:39I've travelled to the north of England to meet a bunch
0:23:39 > 0:23:42of enthusiasts with a head for heights.
0:23:45 > 0:23:49Harry Stringer is from the Pennine Region Balloon Association.
0:23:51 > 0:23:55He's been flying hot air balloons for over 25 years.
0:23:57 > 0:24:01- So, where are we going today?- Well, we'll clear the tree tops here...
0:24:01 > 0:24:04- That sounds like a good start! - Yeah, and then we'll go up
0:24:04 > 0:24:07- to about 1,000 feet.- OK. - Hands on.
0:24:08 > 0:24:10Hands on.
0:24:10 > 0:24:16The very first hot-air balloon, launched in 1783, was the brainchild
0:24:16 > 0:24:20of two brothers called Joseph and Etienne Montgolfier.
0:24:20 > 0:24:22Oh, we're free.
0:24:22 > 0:24:24OK, we're way.
0:24:25 > 0:24:30One story goes that Joseph had been staring into his fireplace one
0:24:30 > 0:24:34evening, when he had the idea of filling a paper bag with hot-air.
0:24:36 > 0:24:40On letting the bag go, he observed that it began to rise.
0:24:41 > 0:24:46And this encouraged the brothers to repeat the experiment, but this time
0:24:46 > 0:24:49with a much larger, purpose-built balloon.
0:25:02 > 0:25:03Until the 1780s,
0:25:03 > 0:25:07the sky was just a place for clouds and birds, and humans certainly
0:25:07 > 0:25:10didn't go up there. But when the first balloons came along,
0:25:10 > 0:25:14people could look up and wonder, what's it like up there?
0:25:14 > 0:25:17And the problem, if you were curious about the sky,
0:25:17 > 0:25:20was that gravity was holding you down to the ground.
0:25:20 > 0:25:24But the really ingenious thing about hot-air balloons is how they use
0:25:24 > 0:25:29heat, together with the force of gravity itself, to get around this.
0:25:38 > 0:25:41The mechanism of these is beautifully simple.
0:25:41 > 0:25:43There's a bag above me, filled with hot-air.
0:25:43 > 0:25:46What the burner does is it allows the balloonist to play around with
0:25:46 > 0:25:49the density of the air by controlling its temperature.
0:25:49 > 0:25:52And as the air inside there is heated up,
0:25:52 > 0:25:55and it could get up to 100 Celsius, it expands.
0:25:58 > 0:26:03As the air expands, its individual molecules push outwards,
0:26:03 > 0:26:06making the air inside the balloon less dense.
0:26:08 > 0:26:11And that's where gravity comes into play.
0:26:11 > 0:26:13Gravity is pulling everything,
0:26:13 > 0:26:15everything I can see, down to the ground.
0:26:15 > 0:26:19But because the air inside the balloon is less dense than the air
0:26:19 > 0:26:23around it, everything around us is being pulled down more,
0:26:23 > 0:26:27so it's squeezing the less dense balloon upwards and so balloonists
0:26:27 > 0:26:30are floating on top of the denser air around them.
0:26:36 > 0:26:39But temperature doesn't just enable a balloon to rise,
0:26:39 > 0:26:42it also controls how it falls.
0:26:47 > 0:26:49So, how do you make us come down?
0:26:49 > 0:26:53We'll have a parachute vent. It's massive. You can see it.
0:26:54 > 0:26:56I could pull this red line...
0:26:56 > 0:27:01- Yeah.- ..and it will open the valve and then I just close it and the
0:27:01 > 0:27:04gulp of hot air loss will cause the balloon to descend.
0:27:18 > 0:27:22- We are safe.- Can we stand up now? - We can. We can.
0:27:23 > 0:27:28The discovery that heating up air could make it expand enough to lift
0:27:28 > 0:27:32people into the skies was a milestone in human innovation.
0:27:34 > 0:27:39And it wasn't long before we began to put that very same heat energy
0:27:39 > 0:27:41to a much more practical purpose.
0:27:53 > 0:27:56It was something that emerged from a very 18th-century problem.
0:28:02 > 0:28:04300 years ago, mine owners in Britain
0:28:04 > 0:28:06were facing a serious crisis.
0:28:12 > 0:28:16Since many ore deposits sat well below the water table,
0:28:16 > 0:28:20they were finding that their mines could go only as deep
0:28:20 > 0:28:23as the drainage technology at the time allowed,
0:28:23 > 0:28:26resulting in many mines going out of business.
0:28:29 > 0:28:34What was needed was a way to haul all that water up to the surface,
0:28:34 > 0:28:37so that the miners could get to the ore below.
0:28:40 > 0:28:46And in 1712, an ironmonger called Thomas Newcomen hit upon the answer,
0:28:46 > 0:28:49with the world's first commercial steam engine.
0:28:52 > 0:28:53And it worked by harnessing
0:28:53 > 0:28:57the immense energy contained within hot steam.
0:29:03 > 0:29:07The principle behind Newcomen's engine is exactly the same one that
0:29:07 > 0:29:09Otto von Guericke had demonstrated.
0:29:09 > 0:29:12And that is how hard air pressure can push,
0:29:12 > 0:29:15especially when there's a vacuum on the other side.
0:29:15 > 0:29:17I've got a plastic bottle here
0:29:17 > 0:29:20with some water in the bottom, and I'm going to put it in the microwave
0:29:20 > 0:29:21to heat the water up.
0:29:26 > 0:29:29What's happening inside the microwave is that the water
0:29:29 > 0:29:32molecules are being given energy and they're not just heating up,
0:29:32 > 0:29:35but some of them are turning into a gas, into steam.
0:29:35 > 0:29:39And that steam is starting to fill up the bottle.
0:29:39 > 0:29:41And it's what happens next that's important.
0:29:45 > 0:29:48Tip it into this water here.
0:29:50 > 0:29:52SHE LAUGHS
0:29:52 > 0:29:57And you can see that what happens is that the bottle has been crushed
0:29:57 > 0:29:59and it's now full of water.
0:29:59 > 0:30:02And the reason for that is that as it filled up with steam,
0:30:02 > 0:30:04the air was pushed out.
0:30:04 > 0:30:06And then when I cooled the steam down,
0:30:06 > 0:30:09it condensed from a gas back into a liquid,
0:30:09 > 0:30:11which takes up much less space.
0:30:13 > 0:30:17So there's a partial vacuum left in bottle and so there was all the air
0:30:17 > 0:30:22pressure pushing in, nothing pushing back, and the bottle was crushed.
0:30:29 > 0:30:32This is the principle that Newcomen used to drive his engine.
0:30:33 > 0:30:37At the heart of Newcomen's engine lay a large metal cylinder,
0:30:37 > 0:30:40housing a piston and filled with hot steam.
0:30:42 > 0:30:48Cooling this steam with water simultaneously created a vacuum
0:30:48 > 0:30:52and caused the weight of the atmosphere to push down on the
0:30:52 > 0:30:54piston, driving the engine.
0:30:54 > 0:30:59The cylinder was then refilled with hot steam and the cycle repeated.
0:31:03 > 0:31:08Soon, Newcomen's steam engines were popping up all over Britain.
0:31:10 > 0:31:14Each one a symbol of heat's ability to perform useful work.
0:31:19 > 0:31:23But Newcomen's design had one major weakness.
0:31:26 > 0:31:29The brilliant thing about steam engines is that they convert heat
0:31:29 > 0:31:33energy, this type of energy you can't really see, into mechanical
0:31:33 > 0:31:36work, the sort of thing that can push pistons
0:31:36 > 0:31:39and turn wheels and do practical things.
0:31:40 > 0:31:45And Newcomen's engine worked, but it was spectacularly inefficient -
0:31:45 > 0:31:48of all the energy and the coal that went in,
0:31:48 > 0:31:52only one or 2% was converted into useful, mechanical work.
0:31:56 > 0:31:58The mystery was why.
0:32:00 > 0:32:02Where was all that heat energy going?
0:32:02 > 0:32:05And what could be done to retrieve it?
0:32:09 > 0:32:12To discover the answer, I've come to Coldharbour Mill in Devon.
0:32:15 > 0:32:17Originally built in 1797,
0:32:17 > 0:32:21it's one of the oldest steam-powered woollen mills left in Britain.
0:32:23 > 0:32:25OK, so we won't kill anybody with the other end...
0:32:27 > 0:32:30John Jasper runs the mill's giant steam engine.
0:32:30 > 0:32:33- Like this.- Like that? - You are a natural. Right.- OK.
0:32:33 > 0:32:37And the first thing any steam engine needs, of course, is steam.
0:32:37 > 0:32:40And today, John's invited me to help him make some.
0:32:44 > 0:32:47- So, tell me about these boilers. - This is a Lancashire boiler.
0:32:47 > 0:32:50It holds 20,000 gallons of water.
0:32:50 > 0:32:53Above that water level, you have steam.
0:32:56 > 0:32:58- And you get a bit of steam...- Great.
0:32:58 > 0:33:00So it's basically a sort of steam kettle.
0:33:00 > 0:33:02So these bits are the heating elements.
0:33:02 > 0:33:05Effectively you're shovelling fire into the heating elements...
0:33:05 > 0:33:08- That's it.- And then all of this is the kettle, which is full of water.
0:33:08 > 0:33:10- That's right.- But instead of coming out of the spout...
0:33:10 > 0:33:12- Yes.- ..it goes to a steam engine.
0:33:12 > 0:33:14It just takes a little longer to get to the boil.
0:33:16 > 0:33:19- I'd better do some more shovelling then!- Yeah.
0:33:23 > 0:33:26The engine here is a descendant of a type that was built to address the
0:33:26 > 0:33:29problem of Newcomen's lost energy.
0:33:32 > 0:33:36It was designed by a Scottish instrument maker called James Watt.
0:33:39 > 0:33:43Watt had recently become familiar with a new theory of heat.
0:33:47 > 0:33:51Creating steam is all about putting heat energy into water,
0:33:51 > 0:33:53but there's this strange observation,
0:33:53 > 0:33:56which is that as you start to heat water up,
0:33:56 > 0:34:00you see the thermometer rise and it goes up and up and up,
0:34:00 > 0:34:03and then it gets to 100 degrees and it won't go any further.
0:34:03 > 0:34:08So you can be pumping in huge amounts of heat energy and yet
0:34:08 > 0:34:10the thermometer isn't moving.
0:34:14 > 0:34:17And that's because once water reaches its boiling point,
0:34:17 > 0:34:23all that heat energy is being used up to turn the water into steam.
0:34:24 > 0:34:28And that led to the idea that there are two forms of heat.
0:34:28 > 0:34:31There's the sort which causes the thermometer to rise,
0:34:31 > 0:34:35but there's another type and that is the energy needed just to turn the
0:34:35 > 0:34:40water from a liquid into a gas at the same temperature.
0:34:40 > 0:34:42And that heat is called latent heat.
0:34:46 > 0:34:50The amount of latent heat needed to turn water from a liquid
0:34:50 > 0:34:53into a gas is enormous.
0:34:54 > 0:34:57And the reason that all this matters for steam engines is that steam
0:34:57 > 0:35:00is expensive in terms of energy.
0:35:00 > 0:35:03And when you've got it, you certainly don't want to waste it.
0:35:09 > 0:35:15It was this revelation that creating steam requires huge amounts
0:35:15 > 0:35:20of latent heat that was one of the main reasons why Newcomen's engine
0:35:20 > 0:35:21was so wasteful.
0:35:24 > 0:35:27At the heart of every steam engine, there's a piston.
0:35:27 > 0:35:29That's where the hot gas molecules
0:35:29 > 0:35:32are pushing to create mechanical work.
0:35:32 > 0:35:37The problem with Newcomen's engine was that in order to reset,
0:35:37 > 0:35:40the water needed to be condensed, cooled down.
0:35:40 > 0:35:42And that happened inside the piston,
0:35:42 > 0:35:45so the metal itself had to be cooled down as well.
0:35:45 > 0:35:50And then you needed to use more steam energy to heat it up again
0:35:50 > 0:35:51to create the next stroke.
0:35:52 > 0:35:56In order to conserve all that valuable steam,
0:35:56 > 0:35:59Watt came up with an ingenious invention.
0:36:03 > 0:36:06Watt's solution was a condenser and this is it.
0:36:08 > 0:36:12So instead of having the condensation happening inside the
0:36:12 > 0:36:16piston, the steam was vented out to a separate chamber and that was
0:36:16 > 0:36:19where the condensation occurred.
0:36:21 > 0:36:24And the reason it was a brilliant solution was that the hot parts of
0:36:24 > 0:36:27the engine stayed hot and the cool parts of the engine stayed cool.
0:36:27 > 0:36:29And much less heat was wasted.
0:36:35 > 0:36:37Watt's great insight
0:36:37 > 0:36:42that the more an engine can conserve heat, the more efficient it will be,
0:36:42 > 0:36:45was a watershed moment in the history of steam power.
0:36:48 > 0:36:50Other improvements followed,
0:36:50 > 0:36:54such as the introduction of steam at high pressure
0:36:54 > 0:36:56to generate even greater force.
0:36:58 > 0:37:01These innovations ushered in a mechanical revolution...
0:37:03 > 0:37:06..founded upon the energy of hot gas molecules.
0:37:09 > 0:37:13But as our population grew and our coal supplies dwindled,
0:37:13 > 0:37:17so we began to turn elsewhere for our energy.
0:37:20 > 0:37:22And in some places,
0:37:22 > 0:37:25that's involved tapping into a different source of heat...
0:37:28 > 0:37:33..one that's responsible for some of the most violent natural phenomena
0:37:33 > 0:37:34on the planet.
0:37:47 > 0:37:50Just a short distance from Reykjavik
0:37:50 > 0:37:53lies one of Iceland's top tourist attractions...
0:37:56 > 0:37:59..an outdoor health spa known as the Blue Lagoon.
0:38:03 > 0:38:05This is the real attraction around here.
0:38:05 > 0:38:09Lovely warm water at 38 Celsius.
0:38:09 > 0:38:12And full of minerals which are apparently very good for you.
0:38:12 > 0:38:15So on a day like today and in a country with a reputation for being
0:38:15 > 0:38:19chilly, this is clearly the perfect place to relax.
0:38:27 > 0:38:32But despite appearances, this is no natural beauty spot.
0:38:32 > 0:38:36In fact, the Blue Lagoon is entirely man-made...
0:38:40 > 0:38:45..fed by hot water from the nearby Svartsengi geothermal power station.
0:38:53 > 0:38:57Every day, Svartsengi produces enough electricity
0:38:57 > 0:39:00for around 130,000 homes.
0:39:04 > 0:39:09And the source of all that power is the same heat energy that created
0:39:09 > 0:39:11Iceland in the first place.
0:39:22 > 0:39:25Down below my feet, the Earth is far hotter than it is up here.
0:39:25 > 0:39:29There's a huge amount of heat energy available, and anything that takes
0:39:29 > 0:39:32advantage of it is known as a geothermal power source,
0:39:32 > 0:39:35literally heat from the Earth.
0:39:35 > 0:39:38The deeper you go, the hotter it gets.
0:39:39 > 0:39:44To tap into that heat, Svartsengi sits above 13 boreholes,
0:39:44 > 0:39:48stretching two kilometres into the rock below.
0:39:52 > 0:39:56The basic premise here is that a mixture of hot water and steam is
0:39:56 > 0:40:00pumped up from deep down and the steam is separated out and sent
0:40:00 > 0:40:04through a turbine that generates 75 megawatts of electricity.
0:40:04 > 0:40:06That goes into the grid.
0:40:06 > 0:40:10And then the same steam comes back around and reheats the water and
0:40:10 > 0:40:12that supplies domestic hot water
0:40:12 > 0:40:15for about 20,000 homes on this peninsula.
0:40:16 > 0:40:18For the engineers around here,
0:40:18 > 0:40:23the hot water beneath their feet is just one massive treasure trove.
0:40:27 > 0:40:32Utilising the heat of the planet itself has allowed us to take steam
0:40:32 > 0:40:34power to a new level.
0:40:40 > 0:40:42But today, scientists are attempting
0:40:42 > 0:40:46to harness another even hotter form of energy...
0:40:49 > 0:40:53..derived from a strange type of matter that here on Earth makes the
0:40:53 > 0:40:56occasional spectacular appearance.
0:41:13 > 0:41:17Inside the University of Manchester's high-voltage lab,
0:41:17 > 0:41:22a team of researchers is getting ready to recreate one of the most
0:41:22 > 0:41:24awesome natural phenomena on the planet.
0:41:27 > 0:41:29Lightning.
0:41:36 > 0:41:38This beast of a device is an impulse generator,
0:41:38 > 0:41:42and this one is capable of generating two million volts
0:41:42 > 0:41:44between the bottom and the top.
0:41:44 > 0:41:46And here's how it works.
0:41:46 > 0:41:49Normally, when you get a voltage, electric charge will flow.
0:41:49 > 0:41:54But here, each of these red things is a capacitor, and so the electric
0:41:54 > 0:41:56charge can't go anywhere. It's stored on the plates.
0:41:56 > 0:41:59And that means that energy is building up.
0:42:06 > 0:42:09And it's this point here that's the important bit
0:42:09 > 0:42:11because when the switch over there is pressed,
0:42:11 > 0:42:16all of that charge is going to get dumped through that point in around
0:42:16 > 0:42:18a millionth of a second.
0:42:20 > 0:42:25Here to show me what that means in practice is Dr Vidy Peesapati.
0:42:25 > 0:42:28So, what we're going to do right now is make sure that no one else can
0:42:28 > 0:42:31walk in, so if you want to press the black button...
0:42:31 > 0:42:34- That one?- Yes. That's the one. - SIREN
0:42:34 > 0:42:37Now it's ready. Now we basically have to set our voltage...
0:42:37 > 0:42:42Under Vidy's supervision, I'm going to trigger a lightning strike...
0:42:42 > 0:42:45- You want to press F4 on the keyboard.- That one?- Yeah.
0:42:46 > 0:42:49..which we'll also capture using a high-speed camera.
0:42:51 > 0:42:54- Now it's charging.- So we can see the voltage going up here.
0:42:54 > 0:42:57Absolutely. So, it takes around 60 seconds for the entire kit to be
0:42:57 > 0:43:00- charged up.- When this gets to the end, we'll be ready to go.
0:43:00 > 0:43:04We'll let the siren go, telling us there's going to be a flashover.
0:43:04 > 0:43:07And it automatically triggers the first stage.
0:43:07 > 0:43:1260 seconds later, and the generator is ready to fire.
0:43:15 > 0:43:17So, when I hear the siren... SIREN
0:43:21 > 0:43:24CRACK
0:43:24 > 0:43:27- That is an echo and a half, isn't it? Wow!- It is very loud.
0:43:27 > 0:43:28And that is basically a sonic boom.
0:43:28 > 0:43:32- It's like a giant electric whip crack.- It is, absolutely.
0:43:33 > 0:43:37But it's only when you play back the slow motion video that you begin to
0:43:37 > 0:43:40see exactly what lightning really is...
0:43:42 > 0:43:43CRACK
0:43:43 > 0:43:47..a superheated channel of air, with so much energy
0:43:47 > 0:43:52that it's become an entirely different form of matter.
0:43:55 > 0:43:59We're used to the idea of three states of matter - solid, liquid and
0:43:59 > 0:44:01gas, but what we've got here is a fourth,
0:44:01 > 0:44:05because the source of all of that light is a plasma.
0:44:10 > 0:44:15From the sun's fiery surface
0:44:15 > 0:44:19to the clouds of interstellar gas known as nebulae,
0:44:19 > 0:44:23plasmas are found across our solar system and beyond.
0:44:25 > 0:44:30And it's this superheated form of matter that scientists are hoping
0:44:30 > 0:44:33will enable them to unlock a brand-new type of energy...
0:44:37 > 0:44:41..by manipulating one of its strangest properties.
0:44:43 > 0:44:47This is a Crookes tube, named after the British physicist William
0:44:47 > 0:44:50Crookes, who was one of the people to design and use it in the 1870s.
0:44:50 > 0:44:55This was the piece of equipment that opened the door to plasma physics.
0:44:55 > 0:44:59It's a sealed glass vessel and it's got two electrodes -
0:44:59 > 0:45:02the negative one here, and a positive one here.
0:45:02 > 0:45:04And on the inside, there's just a little bit of gas
0:45:04 > 0:45:06at very low pressure.
0:45:08 > 0:45:12And when Crookes turned up the voltage, this is what he saw.
0:45:19 > 0:45:22So you can see that this is quite noisy, but there's
0:45:22 > 0:45:26a green glow down this end of the tube.
0:45:27 > 0:45:31Crookes called this eerie light radiant matter.
0:45:34 > 0:45:38Crookes didn't understand what was going on, but we do.
0:45:38 > 0:45:40And it's this.
0:45:40 > 0:45:43When high voltage is applied across the two electrodes,
0:45:43 > 0:45:48it frees up negatively charged electrons from the gas inside
0:45:48 > 0:45:52that are then accelerated towards the flat end of the tube.
0:45:54 > 0:45:58As they strike the glass, they excite the molecules on the surface,
0:45:58 > 0:46:01causing them to give off light.
0:46:04 > 0:46:07And it's the free movement of electrons like this that is the
0:46:07 > 0:46:09defining characteristic of a plasma.
0:46:11 > 0:46:14And which gives it one of its most distinctive properties.
0:46:16 > 0:46:18I've got a magnet here, just a small one.
0:46:18 > 0:46:23When I bring the magnet in here, you can see that beam of electrons is
0:46:23 > 0:46:25being pushed to one side or the other.
0:46:25 > 0:46:28It's being deflected by the magnet.
0:46:31 > 0:46:35So I can actually control what's going on inside a plasma,
0:46:35 > 0:46:37using electric and magnetic fields,
0:46:37 > 0:46:40and that is what makes a plasma really interesting.
0:46:46 > 0:46:52It's this in-built electromagnetism that's opened up the possibility of
0:46:52 > 0:46:57one day channelling the enormous energy inside super hot plasma
0:46:57 > 0:46:58and putting it to use...
0:47:00 > 0:47:05..by exploiting here on Earth a different source of energy,
0:47:05 > 0:47:09the very same type of energy that powers our sun.
0:47:19 > 0:47:24Inside a vast hangar at the Culham Science Centre near Oxford
0:47:24 > 0:47:26sits a machine so complex
0:47:26 > 0:47:30it contains well over 100,000 separate parts.
0:47:32 > 0:47:35This is a fusion reactor.
0:47:35 > 0:47:41Its job is to channel streams of extremely hot plasma and use them
0:47:41 > 0:47:43to manipulate matter at the atomic scale.
0:47:48 > 0:47:53The aim is to unleash the power of the atom itself and reach
0:47:53 > 0:47:55the holy grail of physics.
0:47:57 > 0:47:58Nuclear fusion.
0:48:06 > 0:48:10There's no way anyone would be this close to a fusion reactor if it was
0:48:10 > 0:48:13running because it throws off enormous numbers of neutrons
0:48:13 > 0:48:16which can do a lot of damage and that's why everything
0:48:16 > 0:48:19around me here is surrounded in concrete, three metres thick.
0:48:19 > 0:48:22Just at the moment, they're in a maintenance phase,
0:48:22 > 0:48:24so we can get a little bit closer.
0:48:25 > 0:48:30Here to give me a tour of the reactor is Dr Joanne Flanagan.
0:48:31 > 0:48:35What exactly is it that all of this kit is trying to do?
0:48:35 > 0:48:37We are essentially trying to create an artificial star.
0:48:37 > 0:48:40Actually, we do, we create artificial stars.
0:48:45 > 0:48:49We take hydrogen gas and heat it up to very high temperatures, where it
0:48:49 > 0:48:52becomes ionised, it becomes a plasma.
0:48:52 > 0:48:55What sort of temperatures does it reach on the inside there?
0:48:55 > 0:48:58We routinely reach temperatures of about 100 million degrees,
0:48:58 > 0:49:01which is about ten times hotter than the centre of the sun.
0:49:01 > 0:49:03That's just a ludicrous number!
0:49:03 > 0:49:05It's a number you can't even get your head around.
0:49:05 > 0:49:08It's a crazy hot temperature. We need such high temperatures
0:49:08 > 0:49:10because hydrogen nuclei repel each other.
0:49:10 > 0:49:13To get them to stick, we need them to collide at high speed.
0:49:13 > 0:49:16And that's fundamentally what temperature is.
0:49:16 > 0:49:17High-speed particles.
0:49:17 > 0:49:20Right, how do you make any thing that hot?
0:49:20 > 0:49:23The first step is to run a current through the plasma,
0:49:23 > 0:49:26like an old-style electrical light bulb.
0:49:26 > 0:49:29And that gets us to a few tens of millions of degrees.
0:49:32 > 0:49:36But then we need to pull additional heating systems online to boost us
0:49:36 > 0:49:39- the rest of the way.- So you're just throwing everything at it
0:49:39 > 0:49:41to get energy into it.
0:49:42 > 0:49:46Since there's no material on Earth that can withstand temperatures
0:49:46 > 0:49:51of 100 million degrees, the scientists instead
0:49:51 > 0:49:55contain the plasma by using its electromagnetism.
0:49:58 > 0:50:04At the heart of the reactor lies a giant metal doughnut called a
0:50:04 > 0:50:09tokamak that uses a powerful magnetic field to keep the plasma
0:50:09 > 0:50:11confined long enough for the collisions
0:50:11 > 0:50:13that cause fusion to happen.
0:50:15 > 0:50:21To show me how it works, Jo takes me inside a full-sized mock-up.
0:50:21 > 0:50:24The plasma would be in the space that we're in here and the magnetic
0:50:24 > 0:50:26fields, where do they go?
0:50:26 > 0:50:31The magnetic fields curve around in the shape of the vessel.
0:50:31 > 0:50:34They have a sort of onion-like structure and they hold the plasma
0:50:34 > 0:50:36to the shape of this vessel,
0:50:36 > 0:50:38about five centimetres away from the edges.
0:50:38 > 0:50:41And the plasma is then here in the middle, is it?
0:50:41 > 0:50:43Right where you are.
0:50:43 > 0:50:46As all this plasma is heated up,
0:50:46 > 0:50:49so the hydrogen nuclei inside accelerate,
0:50:49 > 0:50:54getting faster and faster until they reach a speed where they can get
0:50:54 > 0:50:56close enough to fuse.
0:50:59 > 0:51:02So, once you've had a successful collision, what happens next?
0:51:02 > 0:51:07Then you have a very fast neutron that comes out of that reaction.
0:51:07 > 0:51:11So it's the neutrons that are carrying the energy out is their
0:51:11 > 0:51:15- speed.- Yes.- That will go flying off and it will heat something up.
0:51:15 > 0:51:16Yeah.
0:51:20 > 0:51:24The idea is that you would have a lithium blanket surrounding the
0:51:24 > 0:51:25entire device which would capture
0:51:25 > 0:51:28those neutrons and heat up, and you'd have heat
0:51:28 > 0:51:32exchanger pipes that run through that blanket that would then heat
0:51:32 > 0:51:34water to drive the steam turbines.
0:51:38 > 0:51:43But if we're ever to master the searing temperatures of fusion,
0:51:43 > 0:51:47then there's one major obstacle that still has to be overcome.
0:51:50 > 0:51:53Because for now at least, we've yet to find a way of getting
0:51:53 > 0:51:56more energy out from a fusion reactor...
0:51:58 > 0:51:59..than we put in.
0:52:06 > 0:52:10Fusion is such an enticing idea - there's no shortage of fuel,
0:52:10 > 0:52:13there's almost no pollution, it would solve so many problems.
0:52:14 > 0:52:16But impressive as all of this is,
0:52:16 > 0:52:21it might not be the technology that crosses the line first.
0:52:21 > 0:52:23Several years ago,
0:52:23 > 0:52:27an idea came along that it might be possible to generate fusion in a
0:52:27 > 0:52:29tiny bubble of gas inside a liquid.
0:52:32 > 0:52:35Theory had predicted that by collapsing a bubble of gas
0:52:35 > 0:52:41incredibly quickly, it might be possible to get the molecules inside
0:52:41 > 0:52:43to heat up enough for fusion to occur.
0:52:44 > 0:52:47But it couldn't be made to work in practice.
0:52:49 > 0:52:53And the idea was discredited. It was basically thrown away.
0:52:53 > 0:52:55But some new science has been done
0:52:55 > 0:52:58and bubbles are back in the world of fusion.
0:53:07 > 0:53:09Just up the road from the reactor
0:53:09 > 0:53:12is one of the companies behind this technique.
0:53:15 > 0:53:19And I've come to meet its co-founder, Dr Nick Hawker.
0:53:22 > 0:53:25So, Nick, what's your solution to the problem of fusion?
0:53:25 > 0:53:29The idea is instead of trying to hold the plasma together with
0:53:29 > 0:53:32magnetic fields, you use an implosion of some kind
0:53:32 > 0:53:35to both compress and heat the plasma.
0:53:35 > 0:53:38And how do you set that up? How does that work in practice?
0:53:38 > 0:53:40This is a plastic target.
0:53:40 > 0:53:42In the middle is a little spherical cavity.
0:53:42 > 0:53:45And then what we have is a high velocity projectile.
0:53:45 > 0:53:47That comes in and it hits this side here.
0:53:47 > 0:53:50That creates an enormously high pressure on this surface.
0:53:50 > 0:53:52So the idea is that when you compress the gas in there,
0:53:52 > 0:53:54because you do it so quickly, it heats up,
0:53:54 > 0:53:56and that's where the energy comes from?
0:53:56 > 0:53:58That's right, yeah.
0:53:58 > 0:54:00The plasma exists for a few hundred nanoseconds.
0:54:03 > 0:54:06To heat the pocket of gas inside the target,
0:54:06 > 0:54:09Nick and his team hit it with a projectile,
0:54:09 > 0:54:12travelling at almost 30,000 kilometres per hour.
0:54:15 > 0:54:17SIREN
0:54:17 > 0:54:20- Is everything armed? - Everything is now armed.
0:54:22 > 0:54:24Three, two, one, fire.
0:54:29 > 0:54:34By filming the moment of impact with high-speed cameras set to record
0:54:34 > 0:54:36at a billion frames per second,
0:54:36 > 0:54:41the team have been able to capture the precise moment the plasma forms.
0:54:45 > 0:54:49On the left of the screen is the view of the gas pocket from side on.
0:54:51 > 0:54:53And on the right, the view from behind.
0:54:53 > 0:54:55So you can see the shock -
0:54:55 > 0:54:58this dark stuff here is the shock coming through.
0:54:58 > 0:55:02That's the first shock which goes into the gas and even that is enough
0:55:02 > 0:55:04to heat it a lot and it starts to turn...
0:55:04 > 0:55:06Well, it turns into a plasma and starts to glow.
0:55:08 > 0:55:11As the projectile strikes the target,
0:55:11 > 0:55:13the gas collapses in on itself,
0:55:13 > 0:55:19causing the molecules inside to heat up so violently that they emit
0:55:19 > 0:55:22a light, briefly turning into a plasma.
0:55:24 > 0:55:27It's beautiful, isn't it? You get this bright light
0:55:27 > 0:55:29and it's a circle and then it becomes a ring
0:55:29 > 0:55:31and the centre of it goes dark.
0:55:33 > 0:55:36It's a very pretty way of doing it, isn't it?
0:55:36 > 0:55:38This beautiful circle that appears out of nowhere.
0:55:38 > 0:55:40And what sort of temperatures are reached in here?
0:55:40 > 0:55:42Average temperature is something like
0:55:42 > 0:55:45in the tens of thousands of Kelvin.
0:55:50 > 0:55:53So this isn't hot enough for fusion, but you can...
0:55:53 > 0:55:56If you hit it faster, can you reach the temperatures you need?
0:55:56 > 0:55:58Yes, it's all about the velocity.
0:55:58 > 0:56:01We think we need to go two or three times faster than this gun.
0:56:01 > 0:56:03So we're looking at electromagnetically launching
0:56:03 > 0:56:07a projectile to try to get to higher and higher velocities
0:56:07 > 0:56:10and then to the temperatures we need for fusion.
0:56:10 > 0:56:12But potentially you can get a huge amount of energy out of it,
0:56:12 > 0:56:15- if it works. - Well, a cavity this size,
0:56:15 > 0:56:17if you burned all the fuel in there,
0:56:17 > 0:56:19that would release about the same amount of energy as a barrel of oil,
0:56:19 > 0:56:22so it's an enormous amount of energy.
0:56:29 > 0:56:32I think it's very likely that fusion energy,
0:56:32 > 0:56:36this technology made possible by fantastically high temperatures,
0:56:36 > 0:56:40will form a significant power source in the future of our civilisation,
0:56:40 > 0:56:42but the exciting thing about it is
0:56:42 > 0:56:46that we don't know which path it's going to take.
0:56:46 > 0:56:49This is the adventure of science and engineering.
0:56:52 > 0:56:55Even though there's not yet one clear solution,
0:56:55 > 0:56:58when it comes to fusion, the game is afoot.
0:57:04 > 0:57:05In this series,
0:57:05 > 0:57:08we've learned how nothing would exist without temperature.
0:57:09 > 0:57:14From the searing heat of the early Earth
0:57:14 > 0:57:19to the cooling that transformed it and allowed life to flourish,
0:57:19 > 0:57:23temperature has been fundamental to the story of our planet.
0:57:26 > 0:57:29But it has also driven our story.
0:57:31 > 0:57:34As our understanding of temperature has grown,
0:57:34 > 0:57:37so we've learned how to use it...
0:57:39 > 0:57:42..to create new materials,
0:57:42 > 0:57:44drive our machines...
0:57:46 > 0:57:49..and to advance our technology.
0:57:50 > 0:57:56Temperature is such a big idea, encapsulated in just one number.
0:57:56 > 0:57:59As a physicist, it's the first thing I measure.
0:57:59 > 0:58:02And as a human, it's the first thing I feel.
0:58:02 > 0:58:04And yet our direct experience
0:58:04 > 0:58:07of temperature is limited to a really narrow range.
0:58:07 > 0:58:11But once you learn about what's beyond that, the extreme
0:58:11 > 0:58:14heat, the extreme cold, and all the subtleties in between,
0:58:14 > 0:58:19it's clear that the possibilities that temperature offers are endless.