0:00:07 > 0:00:11This is the vibrant heart of a 21st century city.
0:00:11 > 0:00:15There's something strange but wonderful about Piccadilly Circus.
0:00:15 > 0:00:17Strange because, as far as the eye can see,
0:00:17 > 0:00:19there's nothing natural.
0:00:19 > 0:00:23There's not a tree, not a flower, not a blade of grass.
0:00:23 > 0:00:25But wonderful because we made it.
0:00:27 > 0:00:31We've transformed matter to create the world that we live in.
0:00:38 > 0:00:42My name is Mark Miodownik, and as a materials scientist
0:00:42 > 0:00:45I've spent my life trying to understand
0:00:45 > 0:00:47what's hidden deep beneath the surface
0:00:47 > 0:00:50of everything that makes up our modern world.
0:00:57 > 0:01:01For me, the story of how materials have driven human civilisation
0:01:01 > 0:01:04from the Stone Age to the Silicon Age
0:01:04 > 0:01:06is the most exciting story in science.
0:01:08 > 0:01:12Without our mastery of the stuff that we found around us,
0:01:12 > 0:01:15we would have no buildings, no cars,
0:01:15 > 0:01:18no roads, no art.
0:01:18 > 0:01:20Nothing.
0:01:20 > 0:01:24This series is the story of how we created our 21st century world,
0:01:24 > 0:01:28how we unlocked the secrets of the raw materials of our planet
0:01:28 > 0:01:30and created our future.
0:01:42 > 0:01:46Gleaming, lustrous, volatile metals.
0:01:51 > 0:01:54Everything around us is shaped by metal.
0:01:54 > 0:02:00Metal has driven human civilisation - power, war, industry -
0:02:00 > 0:02:03and yet it's mysterious stuff.
0:02:03 > 0:02:06It's only in the last 60 years that we've begun to unravel
0:02:06 > 0:02:09the secrets hidden deep within the metal at the atomic scale,
0:02:09 > 0:02:12how it is that it can be strong enough to build empires
0:02:12 > 0:02:17and yet soft enough that I can crumple it in my hand,
0:02:17 > 0:02:20why it is that it seems inert and unchanging
0:02:20 > 0:02:25and yet sometimes can behave almost as if it's alive.
0:02:28 > 0:02:32Take a look at this. It looks like a normal paperclip,
0:02:32 > 0:02:35but if I scrunch it up so it's unrecognisable
0:02:35 > 0:02:37and then put a blowtorch on it...
0:02:39 > 0:02:40HE LAUGHS
0:02:40 > 0:02:43Isn't that amazing? Isn't that marvellous?
0:02:43 > 0:02:45I mean, that is indistinguishable from magic.
0:02:45 > 0:02:48This... This metal remembers its shape.
0:02:48 > 0:02:50Normal metals don't do this.
0:02:50 > 0:02:53We've engineered this metal to have a memory.
0:02:53 > 0:02:57How we got from the Stone Age to being able to manipulate matter
0:02:57 > 0:03:00and make metals like this is the story of this programme.
0:03:09 > 0:03:13Let me take you back to when it all began -
0:03:13 > 0:03:15the dawn of civilisation.
0:03:24 > 0:03:26This is where our ancestors first settled.
0:03:26 > 0:03:31It's where East meets West, where Africa meets Asia.
0:03:32 > 0:03:35Underneath my feet, the Earth's crust is shifting.
0:03:37 > 0:03:40And the geology here gave our ancestors
0:03:40 > 0:03:44access to something that would change their world.
0:03:46 > 0:03:49This is one of the first places on Earth
0:03:49 > 0:03:52that man stepped out of the Stone Age
0:03:52 > 0:03:55and transformed rock into metal.
0:03:55 > 0:03:58And it all started with copper.
0:03:59 > 0:04:03It's these green streaks that may have been the first clue
0:04:03 > 0:04:05there was something a bit special about this rock.
0:04:05 > 0:04:09Somehow, we worked out that when you've got this type of rock,
0:04:09 > 0:04:13you can do something amazing with it.
0:04:17 > 0:04:20We don't really know when our ancestors first discovered
0:04:20 > 0:04:23what this marvellous green rock can do.
0:04:23 > 0:04:25They might have just ground it up
0:04:25 > 0:04:28to use it as a powder to decorate their pottery,
0:04:28 > 0:04:32or maybe it happened to be just lying by the fire.
0:04:32 > 0:04:35But either way, they discovered something really rather marvellous
0:04:35 > 0:04:38about what this stuff can do if you add it to a fire.
0:04:38 > 0:04:43Now, the thing about the fire is, you need it to be very, very hot
0:04:43 > 0:04:46and for that you need a lot of air,
0:04:46 > 0:04:48and that's why they built their fires on hillsides.
0:04:48 > 0:04:51These hillsides are extremely windy,
0:04:51 > 0:04:53so the air is being funnelled into the fire.
0:04:53 > 0:04:56It's actually a genius idea.
0:04:56 > 0:04:58And then, when they'd got a very hot fire,
0:04:58 > 0:05:01they added the green rock.
0:05:01 > 0:05:05And then they kept the temperature high for hours, and they waited.
0:05:12 > 0:05:15So when the fire died down,
0:05:15 > 0:05:20they would have found bits of a hard stone, black stone,
0:05:20 > 0:05:22but amongst that black stone,
0:05:22 > 0:05:26look, there's tiny little shiny bits of metal.
0:05:26 > 0:05:30They'd transformed rock into metal, it's absolutely extraordinary!
0:05:30 > 0:05:34Here we have rock... I mean, there's rock everywhere,
0:05:34 > 0:05:36but they'd found the power of transformation.
0:05:39 > 0:05:43Look! Look how bright that is! A bright piece of copper.
0:05:43 > 0:05:47We know they did it on this hillside because we've found the remnants
0:05:47 > 0:05:50from early smelting of our ancestors.
0:05:50 > 0:05:52So they did that here,
0:05:52 > 0:05:56and this was the beginning of human civilisation,
0:05:56 > 0:05:58the age of metals.
0:06:11 > 0:06:14Our ancestors realised that with copper,
0:06:14 > 0:06:16they could make strong tools,
0:06:16 > 0:06:19better than anything they'd had before.
0:06:19 > 0:06:23This copper chisel represents the leap out of the Stone Age.
0:06:23 > 0:06:26Everything we have in our civilisation today
0:06:26 > 0:06:28is due to metal tools like this.
0:06:28 > 0:06:30If they get blunt, we can sharpen them.
0:06:30 > 0:06:32If they get bent, we can re-straighten them.
0:06:32 > 0:06:35If they get damaged, we can repair them.
0:06:35 > 0:06:37It's simply the perfect material for tools.
0:06:39 > 0:06:42Nothing else our ancestors had in their world
0:06:42 > 0:06:47could have done this - not stone, not bone, not wood.
0:06:49 > 0:06:52So what's so special about metal?
0:06:52 > 0:06:55It's all down to its inner structure.
0:06:57 > 0:07:01Metals are made of crystals, and that's a very surprising fact,
0:07:01 > 0:07:03because they don't seem to behave
0:07:03 > 0:07:06anything like the crystals we are more familiar with.
0:07:06 > 0:07:09I'll show you what I mean. I've got a quartz crystal here.
0:07:09 > 0:07:12That's what you mean when you say "crystal".
0:07:12 > 0:07:16And this is what a quartz crystal says when you hit it with a hammer.
0:07:19 > 0:07:21You see? That's what we think of
0:07:21 > 0:07:24when we think of crystals being hit with a hammer.
0:07:24 > 0:07:28But if I say to you that this piece of metal is made of crystals,
0:07:28 > 0:07:31you know already that it's not going to do that.
0:07:31 > 0:07:34It's going to be quite malleable, I can do this.
0:07:34 > 0:07:37In fact, that's how you work metal, you change its shape.
0:07:37 > 0:07:42And that's...that's really strange, because that means
0:07:42 > 0:07:46that the crystals in this metal are changing shape instead of exploding.
0:07:47 > 0:07:49Inside the metal crystal,
0:07:49 > 0:07:53the basic building blocks of everything in the universe, atoms,
0:07:53 > 0:07:56are arranged in a regular lattice structure.
0:07:56 > 0:07:58But they're not static.
0:08:00 > 0:08:04When they're hit, metals can shuffle atoms from one side to the other,
0:08:04 > 0:08:06like a Mexican wave.
0:08:08 > 0:08:11They can move, rearrange themselves,
0:08:11 > 0:08:14and this is why the crystal can change shape.
0:08:16 > 0:08:18Metals alone behave like this.
0:08:18 > 0:08:22As well as not shattering when you hit them,
0:08:22 > 0:08:24they actually get stronger.
0:08:28 > 0:08:30The impact creates waves of shuffling atoms
0:08:30 > 0:08:34which collide with each other and create blockages.
0:08:34 > 0:08:37These make it harder for the atoms to shuffle around,
0:08:37 > 0:08:39making the metal stronger.
0:08:42 > 0:08:44So the more hammering you do,
0:08:44 > 0:08:46the more blockages you form in the crystal,
0:08:46 > 0:08:48and so the stronger the metal gets.
0:08:52 > 0:08:55It was the strength of metal over stone and wood
0:08:55 > 0:08:58that became its main attraction.
0:09:02 > 0:09:04With metal tools,
0:09:04 > 0:09:09our ancestors could conceive of grandiose projects.
0:09:09 > 0:09:13It's believed the limestone blocks that built the pyramids of Egypt
0:09:13 > 0:09:15were carved using copper chisels.
0:09:19 > 0:09:22But soon copper wasn't enough.
0:09:22 > 0:09:25Our love affair with metals consumed us.
0:09:25 > 0:09:28Here on the shores of what's now Israel,
0:09:28 > 0:09:32metals from distant lands were traded.
0:09:33 > 0:09:37And it was one of these, tin, that moved on the story of metals,
0:09:37 > 0:09:42as our ancestors began to mix metals together.
0:09:42 > 0:09:46So they took some copper...some tin,
0:09:46 > 0:09:49and they melted them together to make a mixture,
0:09:49 > 0:09:51which we call an alloy.
0:09:51 > 0:09:54And they created a new metal, bronze.
0:09:57 > 0:09:59Bronze was the creation of man the metal-smith,
0:09:59 > 0:10:01rather than a gift of nature,
0:10:01 > 0:10:06and it gave its name to a new era, the Bronze Age.
0:10:07 > 0:10:10Now, this is a nail made out of pure copper,
0:10:10 > 0:10:14and as metals go, copper's pretty weak.
0:10:14 > 0:10:16Have a look at this.
0:10:20 > 0:10:23After a while, it just can't get any further,
0:10:23 > 0:10:26and so the metal itself buckles.
0:10:26 > 0:10:30If I do the same with tin nail... let's see what happens.
0:10:30 > 0:10:32Tin is actually softer than copper, even.
0:10:34 > 0:10:37That's a real joke for a nail, isn't it?
0:10:37 > 0:10:38But here's the odd thing.
0:10:38 > 0:10:42The mixture, a bronze nail...
0:10:42 > 0:10:44well, this is much stronger.
0:10:46 > 0:10:47Ha-ha-ha-ha!
0:10:48 > 0:10:51It's so strong it's knocking the wood out of this vice.
0:10:53 > 0:10:56So that's odd, isn't it? You add two soft metals together,
0:10:56 > 0:11:00and you get something much harder and much stronger.
0:11:00 > 0:11:01How do you explain that?
0:11:04 > 0:11:07In bronze, the tin atoms replace some of the copper atoms,
0:11:07 > 0:11:09which are smaller.
0:11:09 > 0:11:13This interferes with the lattice structure,
0:11:13 > 0:11:17making it more difficult for the atoms to shuffle across the crystal.
0:11:17 > 0:11:20This makes the new alloy much stronger.
0:11:24 > 0:11:26The strength of bronze
0:11:26 > 0:11:29gave us the means not only to build, but to destroy.
0:11:30 > 0:11:32As well as tools,
0:11:32 > 0:11:36we made the swords and shields of conquest and dominion.
0:11:38 > 0:11:39Bronze propelled the evolution
0:11:39 > 0:11:43of a new, complex, more technological society.
0:11:43 > 0:11:46It also created new occupations,
0:11:46 > 0:11:49such as mining, manufacturing and trading metals.
0:11:50 > 0:11:54Bronze dominated the world for 2,000 years.
0:11:56 > 0:12:00But it wasn't the metal to take us into the industrial age.
0:12:00 > 0:12:04About 1200 BC, another metal rose to prominence.
0:12:05 > 0:12:08Iron.
0:12:08 > 0:12:13Iron is one of the most plentiful elements in the Earth's crust,
0:12:13 > 0:12:17but it's fiendishly difficult to work with.
0:12:19 > 0:12:25Owen Bush has spent nearly 20 years learning how to tame iron.
0:12:25 > 0:12:27It doesn't look very promising
0:12:27 > 0:12:30as a way to start a civilisation, does it?
0:12:30 > 0:12:34- It's the basics, the beginning of it. - So what happens next?
0:12:34 > 0:12:37- You take this stuff...- Heat it up. - OK.- And hit it.
0:12:42 > 0:12:48Pure iron can't be easily extracted from its native rock.
0:12:49 > 0:12:54There are several stages before it can be hammered into submission.
0:12:55 > 0:12:57So this whole process of bashing it
0:12:57 > 0:13:01and putting it back in the furnace is to get purer and purer iron.
0:13:01 > 0:13:03- Yes, it is.- You're trying to purify
0:13:03 > 0:13:07this very strange substance that's come out of the furnace.
0:13:07 > 0:13:10Yeah, I'm literally beating the crap out of it.
0:13:12 > 0:13:15As Owen continues to hammer the iron,
0:13:15 > 0:13:21more and more impurities are exposed to the air and burn off as sparks.
0:13:21 > 0:13:26By bashing it, you're left with a purer metal.
0:13:26 > 0:13:28This is wrought iron,
0:13:28 > 0:13:31wrought at the blacksmith's anvil.
0:13:31 > 0:13:33If you'd like to have a bash, by all means.
0:13:33 > 0:13:36I would love to do that, I've never done that before.
0:13:36 > 0:13:42Mastery of iron by our ancestors would not have been easy.
0:13:42 > 0:13:45To show me just how difficult it is to work with, Owen challenges me
0:13:45 > 0:13:49to make the simplest and most common of iron products.
0:13:49 > 0:13:52Well, we're going to try and squash it flat and forge a nail out of it.
0:13:52 > 0:13:55I know in theory what this stuff should do,
0:13:55 > 0:14:00but I've never hit it with a hammer, I've never done what you do.
0:14:00 > 0:14:01- That's good to go.- OK.
0:14:01 > 0:14:02Right.
0:14:04 > 0:14:08- That's it.- Oh, yeah, so there's bits flying off, I can really feel...
0:14:08 > 0:14:10You can feel something happening in the metal.
0:14:10 > 0:14:13There's a kind of response to you.
0:14:13 > 0:14:17- There's something addictive to this. - Yeah, it's primal, isn't it?- Yeah!
0:14:17 > 0:14:20- Now, yeah, back in.- Back in, yeah.
0:14:20 > 0:14:22You can see, when it came out, it was bubbling,
0:14:22 > 0:14:24and as it cools down the...
0:14:24 > 0:14:26Yeah, then I can see it becoming a bit brittle.
0:14:26 > 0:14:31It sort of freezes in your hands and you're not making any headway.
0:14:31 > 0:14:34Yeah, well, you're getting feedback from it,
0:14:34 > 0:14:37and because every bit's different, you have to use that feedback
0:14:37 > 0:14:42so you don't end up with a flattened, destroyed blob, fundamentally.
0:14:49 > 0:14:51What I began to learn with Owen
0:14:51 > 0:14:54is just how much of this process is trial and error,
0:14:54 > 0:14:58how different iron ores could behave very differently.
0:14:58 > 0:15:02All the variables of heat, of ore, of fuel
0:15:02 > 0:15:05meant that the quality of your iron
0:15:05 > 0:15:08depended absolutely on the quality of your blacksmith.
0:15:11 > 0:15:14You're just hammering down to give it a bit of a head.
0:15:16 > 0:15:17Lovely.
0:15:18 > 0:15:20That's quite satisfying.
0:15:20 > 0:15:22You got some good hits in there.
0:15:22 > 0:15:24There we have our little nail.
0:15:24 > 0:15:28What a beauty! My first nail.
0:15:29 > 0:15:30And it was the iron nail
0:15:30 > 0:15:33that was to underpin the next great civilisation.
0:15:38 > 0:15:42The Romans were expert at manipulating iron.
0:15:42 > 0:15:45Their blacksmiths travelled everywhere with them,
0:15:45 > 0:15:48forging the weapons and shields of Empire.
0:15:52 > 0:15:56But the Romans never built big with iron.
0:15:56 > 0:16:00They were limited by what the blacksmith could do at his anvil.
0:16:03 > 0:16:06And so, we would be constrained for another 1,500 years
0:16:06 > 0:16:11until the next great step in our mastery of metals
0:16:11 > 0:16:15a new technology that would unleash the Industrial Revolution.
0:16:15 > 0:16:19Ironbridge Gorge in Shropshire was at the heart of this new revolution.
0:16:19 > 0:16:22A man called Abraham Darby started making iron pots
0:16:22 > 0:16:24and, almost overnight,
0:16:24 > 0:16:28he turned this sleepy valley into the iron capital of England.
0:16:33 > 0:16:35The key was the fuel.
0:16:35 > 0:16:39Darby realised that, with fires made from coke,
0:16:39 > 0:16:42partially burned coal, he could reach much higher temperatures.
0:16:42 > 0:16:46And that would do something that would transform iron.
0:16:51 > 0:16:53When it got hot enough, something happened
0:16:53 > 0:16:56that opened up vast new possibilities for iron.
0:16:56 > 0:16:58It melted and became liquid.
0:16:59 > 0:17:03This was the birth of a new type of iron cast iron.
0:17:09 > 0:17:1318th century engineers must barely have been able
0:17:13 > 0:17:14to contain their excitement.
0:17:14 > 0:17:19Now, instead of working iron at an anvil,
0:17:19 > 0:17:21they could pour it into a mould.
0:17:21 > 0:17:24And the mould could be any shape or size they wanted.
0:17:30 > 0:17:34Darby's furnaces worked around the clock.
0:17:34 > 0:17:36They turned the night sky red.
0:17:36 > 0:17:39And the roar could be heard for miles around.
0:17:39 > 0:17:44There seemed no limit to what this exuberant new industry could do.
0:17:44 > 0:17:48And this was proof of it. It was built by Abraham Darby's grandson.
0:17:48 > 0:17:52And it was the first iron bridge in the world.
0:18:07 > 0:18:09This was a golden age of engineering,
0:18:09 > 0:18:13when it seemed only our imaginations could limit us.
0:18:13 > 0:18:16We crossed whole countries with iron railways.
0:18:16 > 0:18:18We crossed rivers with iron bridges.
0:18:18 > 0:18:20TRAIN WHISTLE SOUNDS
0:18:20 > 0:18:23The engineers of the industrial world
0:18:23 > 0:18:27were seduced into thinking that their every ambition was achievable.
0:18:30 > 0:18:33But, the dreams were about to come crashing down.
0:18:33 > 0:18:38On 1st June, 1878, the great and the good of Victorian Britain
0:18:38 > 0:18:43were assembled by the banks of the River Tay here in Dundee
0:18:43 > 0:18:47to applaud the opening of the longest bridge in the world.
0:18:57 > 0:18:59It had been designed by Thomas Bouch,
0:18:59 > 0:19:02an ambitious railway engineer, who may have considered
0:19:02 > 0:19:05the Tay Bridge a stepping stone to a knighthood.
0:19:07 > 0:19:11But, one dark winter's night in 1879 would change all that.
0:19:13 > 0:19:17A train left Edinburgh, north, on the Aberdeen line.
0:19:17 > 0:19:20Storms were raging across the country.
0:19:20 > 0:19:22And when the train got to the Tay,
0:19:22 > 0:19:26gale force winds were ripping through here.
0:19:26 > 0:19:30As the train crossed the bridge, something terrible happened.
0:19:30 > 0:19:34The iron girders cracked, and the bridge collapsed.
0:19:34 > 0:19:37The train plunged into the icy waters.
0:19:39 > 0:19:40There were no survivors.
0:19:42 > 0:19:45It was a terrible human tragedy.
0:19:45 > 0:19:49But what made it worse was that it was a man-made tragedy.
0:19:49 > 0:19:52The pinnacle of our engineering achievement,
0:19:52 > 0:19:54the iron bridge, had failed.
0:19:57 > 0:20:00Nobody had any idea why.
0:20:00 > 0:20:02It was a Victorian mystery.
0:20:17 > 0:20:21I asked Rhona Rogers, from Dundee Museum, how events unfolded that night.
0:20:21 > 0:20:26A couple of hours after the train had plunged into the water,
0:20:26 > 0:20:29crowds began to gather on the north side of the bridge.
0:20:29 > 0:20:33People looking for loved ones that were expected home
0:20:33 > 0:20:36waited for news with none coming.
0:20:36 > 0:20:39Tell me about Thomas Bouch, how did he react?
0:20:39 > 0:20:43He was on the boat the next day that went out
0:20:43 > 0:20:46to look for survivors or any signs of the wreckage,
0:20:46 > 0:20:50and he was described as being in a very sorry state.
0:20:50 > 0:20:55And he rapidly became very ill and then died a couple of months later.
0:20:55 > 0:21:01He died from water on the lung, that's the official cause of death,
0:21:01 > 0:21:04but a lot of people say it was shame and stress,
0:21:04 > 0:21:08the shame and stress of what had happened, about his loss of career
0:21:08 > 0:21:11and not becoming the success in life he had wanted.
0:21:11 > 0:21:14How did the rest of the country react?
0:21:14 > 0:21:16Was it just a local tragedy?
0:21:16 > 0:21:20No, it was the longest bridge of its type at this time in the world,
0:21:20 > 0:21:24so reactions were global.
0:21:24 > 0:21:27It affected engineering on a world scale.
0:21:27 > 0:21:30And it was a very personal thing for people in Dundee.
0:21:30 > 0:21:33Quite significant, isn't it, that you can still see the remnants of the bridge now?
0:21:33 > 0:21:36They're like tombstones, aren't they?
0:21:36 > 0:21:39Yes, a permanent memorial to the dead, yes,
0:21:39 > 0:21:44the 75 who lost their lives, of which only 45 were washed ashore.
0:21:45 > 0:21:50The cornerstone of the Industrial Revolution - cast iron -
0:21:50 > 0:21:53had failed catastrophically.
0:21:53 > 0:21:56Now the burning question was, why?
0:21:59 > 0:22:01In the immediate aftermath of the disaster,
0:22:01 > 0:22:04there were many theories as to what had gone wrong.
0:22:04 > 0:22:07I've come to Sheffield University to test my own theory.
0:22:10 > 0:22:14Postgraduate students Ben Thomas and Lucy Johnson have designed
0:22:14 > 0:22:18and built a scale model of one of the bridge's iron pillars,
0:22:18 > 0:22:21and we're going to put it to the test.
0:22:23 > 0:22:26So, just like in the real structure, you had these cast irons and this cross brace stuff
0:22:26 > 0:22:31- is exactly how the piers of this railway bridge were constructed? - Yeah.
0:22:31 > 0:22:35'The corners of each pier of the bridge were made of cast iron,
0:22:35 > 0:22:37'and that's what we're testing today.
0:22:39 > 0:22:43'The first test is to see how good the pillar is at carrying loads under compression.'
0:22:45 > 0:22:50'Could the cast iron have collapsed just under the weight of the train?'
0:22:50 > 0:22:53Cast iron's supposed to be quite strong in compression,
0:22:53 > 0:22:56so we've got a very simple compression test straight through the middle here.
0:22:58 > 0:23:01'We started to apply pressure to the model.
0:23:01 > 0:23:04'But before the pillar gave way, this happened...'
0:23:04 > 0:23:06LOUD METALLIC CLANG
0:23:06 > 0:23:11Oh dear, what was that? What happened there?
0:23:11 > 0:23:15There's no obvious breaks, which is good news.
0:23:15 > 0:23:20It may be that it started to crack up here on the test rig.
0:23:20 > 0:23:21Really?
0:23:21 > 0:23:25- So we might have broken the test rig...- No, don't say that!
0:23:25 > 0:23:27Lucy, give me hope.
0:23:27 > 0:23:32- We can't see that anything's obviously broken with the bridge itself.- OK.
0:23:32 > 0:23:35So, the good news is that the bridge is stronger than our test rig?
0:23:35 > 0:23:36It looks that way, yeah.
0:23:36 > 0:23:40'Cast iron is known to be strong under compression,
0:23:40 > 0:23:44'and the bridge had taken the weight of the train many times before.
0:23:44 > 0:23:48'But there were other forces at play on the bridge that night,
0:23:48 > 0:23:50'not least the strong winds.'
0:23:50 > 0:23:55So, because of the wind, the gale force winds, there were forces
0:23:55 > 0:23:59on these cast iron struts that would be making them bend that way.
0:23:59 > 0:24:02They were all trying to bend over like a tree in the wind,
0:24:02 > 0:24:05and the question is, can that material take that kind of force?
0:24:07 > 0:24:10'In that situation, one side of the bridge will be compressed,
0:24:10 > 0:24:13'but the other side will stretch.
0:24:13 > 0:24:17'So I took a single bar from the model
0:24:17 > 0:24:20'and this time I put it in a machine that tests the metal under tension.
0:24:21 > 0:24:24'I'm going to see what happens when you stretch it.'
0:24:25 > 0:24:26BANG
0:24:26 > 0:24:29'With very little force, it snaps.'
0:24:32 > 0:24:36'At the point where the bar broke is evidence of what makes cast-iron weak.'
0:24:36 > 0:24:40Look at where it's fractured. There's this enormous hole there.
0:24:40 > 0:24:45That is an impurity in the material which has very little strength,
0:24:45 > 0:24:48and when you use a microscope to look at this material
0:24:48 > 0:24:52you see not only big flaws in it, like these strange holes,
0:24:52 > 0:24:56but deep inside the metal there are loads of little black blobs,
0:24:56 > 0:25:01black-grey blobs, and they are a material called graphite.
0:25:01 > 0:25:06They're embedded in the material, and there's no way to remove them,
0:25:06 > 0:25:09you can make them smaller but they are always going to be in cast iron.
0:25:11 > 0:25:15It's the very process of making cast iron that causes its weakness.
0:25:15 > 0:25:18The casting process traps in many of the impurities
0:25:18 > 0:25:21that a blacksmith would have hammered out.
0:25:23 > 0:25:26The most important one is graphite - carbon.
0:25:29 > 0:25:34It forms lumps that sit within the microstructure of the metal.
0:25:34 > 0:25:36And it's these lumps that make the metal weak.
0:25:38 > 0:25:39This is what graphite looks like.
0:25:39 > 0:25:42You know it, because it's the stuff of your pencil.
0:25:42 > 0:25:44It's a very weak material,
0:25:44 > 0:25:48so if you have loads of this stuff embedded in your iron,
0:25:48 > 0:25:52it's not surprising that that iron is going to be weak.
0:25:53 > 0:25:57But back in the 19th century, this interior world of metals
0:25:57 > 0:25:59was still hidden from us.
0:26:03 > 0:26:07What it comes down to is this - we were building bridges out of iron
0:26:07 > 0:26:09without fully understanding the material.
0:26:09 > 0:26:12We needed to change our relationship with metal
0:26:12 > 0:26:14from one of mastery to one of understanding.
0:26:16 > 0:26:20All we really knew was that cast iron had failed us.
0:26:20 > 0:26:23We desperately needed a stronger metal.
0:26:24 > 0:26:27But the answer wouldn't lie in making the purist iron possible.
0:26:27 > 0:26:30It would turn out to be far more complex.
0:26:33 > 0:26:38The Victorian engineers looked to history for the strongest iron they could find.
0:26:40 > 0:26:44The metal smiths of old used it to make swords of legendary strength.
0:26:45 > 0:26:48They called it 'good iron'.
0:26:48 > 0:26:50We call it steel.
0:26:53 > 0:26:58Back in the forge, Owen is going to reveal the secret of good iron -
0:26:58 > 0:27:02making the iron pure, but not too pure.
0:27:03 > 0:27:07Following the techniques of ancient swordsmiths,
0:27:07 > 0:27:11he hammers the iron and then folds, and heats and folds again,
0:27:11 > 0:27:16exposing more and more of the iron to the air, so the impurities burn away.
0:27:19 > 0:27:22So I'm just going to cut it in half...
0:27:24 > 0:27:26Then bend it back on itself.
0:27:30 > 0:27:31Back in the fire.
0:27:31 > 0:27:34We had four layers, now we've got eight, next fold 16.
0:27:34 > 0:27:38If this was to be the edge material of the blade I'd probably
0:27:38 > 0:27:41take it up to somewhere between 700 and couple of thousand layers.
0:27:41 > 0:27:42A thousand layers?
0:27:49 > 0:27:53- So what's coming off the edge there? - That's iron oxide.
0:27:53 > 0:27:55- So that's its skin, really?- Yeah.
0:27:57 > 0:28:02'Through a combination of skill and experience the swordsmiths knew
0:28:02 > 0:28:06'when their metal was pure enough to hammer into a blade.
0:28:07 > 0:28:11'Then they added at touch of magic - it's called quenching.
0:28:13 > 0:28:16'They thrust the red hot blade into a cooling liquid.
0:28:19 > 0:28:23'When they drew it out again the edge had hardened.'
0:28:24 > 0:28:27When you read the accounts written down about this process,
0:28:27 > 0:28:31you find all sorts of weird materials,
0:28:31 > 0:28:36like, people would get the urine of a redheaded boy,
0:28:36 > 0:28:40or they'd get a goat which had only fed on the fern for three days
0:28:40 > 0:28:43and they would quench into that - what do you think about this?
0:28:43 > 0:28:50If it worked, if your master smith taught you to quench in the urine of a redheaded boy,
0:28:50 > 0:28:54then if it worked for him there's no reason why you'd stop.
0:28:54 > 0:28:55And, also it adds mystique, doesn't it?
0:28:55 > 0:28:59'Technique and temperature worked a mysterious alchemy,
0:28:59 > 0:29:03'creating a metal that kept its sharp edge.
0:29:03 > 0:29:06'A metal with almost magical properties.'
0:29:08 > 0:29:12The master swordsmiths had manipulated iron so skilfully
0:29:12 > 0:29:15they had unwittingly created a totally new metal.
0:29:15 > 0:29:17Steel.
0:29:17 > 0:29:21The strong, reliable metal the Victorian engineers needed
0:29:21 > 0:29:23to fulfil their growing ambitions.
0:29:26 > 0:29:29But the problem is, as we've just seen,
0:29:29 > 0:29:32it takes a huge amount of time, effort, expertise,
0:29:32 > 0:29:35to just make this one, small blade.
0:29:35 > 0:29:37So, if the Victorians were going to use steel,
0:29:37 > 0:29:40they were going to have to learn how to mass-produce it.
0:29:40 > 0:29:45And in order to do that they would have to find out what was going on inside this metal.
0:29:47 > 0:29:51A clue would come from another feature of the swordsmith's art.
0:29:51 > 0:29:56The pattern of the sword was the must-have mark of quality.
0:29:57 > 0:30:01Dipping the swords in acid made the intricate swirling patterns,
0:30:01 > 0:30:06created by the folding, twisting and hammering, become more pronounced.
0:30:07 > 0:30:10This process was called etching.
0:30:11 > 0:30:16And etching would be the key to revealing the secret of steel,
0:30:16 > 0:30:19exactly what it was made of.
0:30:20 > 0:30:26Here in Sheffield, in 1863, the single-minded dedication
0:30:26 > 0:30:29of one man provided the flash of insight that changed everything.
0:30:32 > 0:30:36Henry Clifton Sorby was perhaps the last great scientific amateur
0:30:36 > 0:30:41in an age when science was becoming the concern of professionals.
0:30:41 > 0:30:46Sorby pretty much invented the idea of looking at metals through microscopes.
0:30:46 > 0:30:49He was ridiculed by his colleagues.
0:30:51 > 0:30:54But he persevered, and it's lucky for as he did.
0:30:54 > 0:30:57Here, I'm proud to say, I have in front of me
0:30:57 > 0:31:00the original samples he first made.
0:31:01 > 0:31:05Sorby prepared his steel samples in exactly the same way
0:31:05 > 0:31:08as the ancient sword Smiths - he etched them.
0:31:10 > 0:31:14And when he looked at the intricate patterns under the microscope,
0:31:14 > 0:31:17Sorby discovered the secret of steel's strength.
0:31:19 > 0:31:23This is a 150-year-old sample that he prepared.
0:31:23 > 0:31:28Let me show you what he saw and no-one else had ever seen.
0:31:29 > 0:31:36The microscope revealed that steel was a very pure form of iron, much purer than cast-iron.
0:31:36 > 0:31:39But there's still a small amount of impurity there.
0:31:39 > 0:31:44The dark bits that look like rivers are crystals that contain carbon.
0:31:45 > 0:31:49It turned out the whole premise of the iron industry had been false.
0:31:49 > 0:31:53Everyone had thought that what you had to do was beat out the impurities -
0:31:53 > 0:31:56the purer the iron you could get the better it would be -
0:31:56 > 0:31:57And they were wrong.
0:31:58 > 0:32:04Instead, what was needed was precisely the right amount of impurity.
0:32:04 > 0:32:08An alloy of iron and carbon in exactly the right proportions.
0:32:12 > 0:32:15This is the crystal lattice of pure iron.
0:32:17 > 0:32:19And this is steel.
0:32:21 > 0:32:23Carbon atoms sit in the gaps between the iron atoms,
0:32:23 > 0:32:25making steel much stronger.
0:32:27 > 0:32:30But you have to have just the right amount of carbon.
0:32:33 > 0:32:36In cast iron, there's too much carbon
0:32:36 > 0:32:40and the spare carbon atoms form larger blobs within the crystal
0:32:40 > 0:32:42and make the metal weaker.
0:32:49 > 0:32:52Now we knew what made steel so strong.
0:32:54 > 0:32:57But we were still in the dark about how to produce it cheaply
0:32:57 > 0:33:02and on the industrial scale that the 19th-century demanded.
0:33:03 > 0:33:07One day, a Sheffield-based engineer called Henry Bessemer
0:33:07 > 0:33:10stood up at a British science meeting and shocked his audience
0:33:10 > 0:33:13by announcing he could mass-produce steel.
0:33:13 > 0:33:17It required no hammering, no beating, no folding.
0:33:17 > 0:33:22He could make tonnes of the stuff in this, his Bessemer converter.
0:33:27 > 0:33:32This huge bucket that Bessemer designed would have contained
0:33:32 > 0:33:34an enormous amount of molten iron,
0:33:34 > 0:33:37and that, of course, was full of carbon.
0:33:37 > 0:33:42So what Bessemer suggested was that you made this pipe that goes down the bottom here,
0:33:42 > 0:33:46and they pumped air through the liquid iron,
0:33:46 > 0:33:49and that air contained oxygen, and the oxygen reacted
0:33:49 > 0:33:53with the carbon to create carbon dioxide.
0:33:53 > 0:33:57And Bessemer's idea was to just do that long enough to get
0:33:57 > 0:34:00the carbon content of the iron down to about 1%.
0:34:00 > 0:34:04And he designed these enormous cranks on the side here,
0:34:04 > 0:34:08so when the carbon content of the steel is exactly right
0:34:08 > 0:34:11you just crank the whole bucket over and out pours masses
0:34:11 > 0:34:14and masses of this beautiful, liquid steel.
0:34:19 > 0:34:24'I'm going to make steel in a way that's based on Bessemer's principle.
0:34:24 > 0:34:30'Molten iron, which is full of impurities like carbon, is poured into a bucket.
0:34:30 > 0:34:32'I blow oxygen through it,
0:34:32 > 0:34:35'just as air was blown through Bessemer's converter.
0:34:35 > 0:34:39'The oxygen reacts with a carbon to form carbon dioxide,
0:34:39 > 0:34:42'removing most of the carbon.
0:34:42 > 0:34:47'So you should be left with just the right amount of carbon to make steel.'
0:34:49 > 0:34:51Well, the process may be simple, but it's insane.
0:34:51 > 0:34:56I mean you are pumping oxygen or air through a liquid metal,
0:34:56 > 0:34:59and it gets white hot and it's bubbling and you think,
0:34:59 > 0:35:01this is fine, making a small cauldron of it,
0:35:01 > 0:35:05but imagine making a bucket load of the stuff the size of this room!
0:35:05 > 0:35:07That's what Bessemer was doing, and having a go at it
0:35:07 > 0:35:11I realise quite how avant-garde he was.
0:35:11 > 0:35:13What he was proposing was really extraordinary.
0:35:15 > 0:35:19But the process had a major disadvantage - it just didn't work.
0:35:22 > 0:35:25It was too difficult to hit precisely
0:35:25 > 0:35:28the right amount of carbon - just under 1%.
0:35:30 > 0:35:33Bessemer and his converter faced financial ruin.
0:35:36 > 0:35:37But not for long.
0:35:39 > 0:35:44British metallurgist Robert Forester Mushet came to his rescue.
0:35:46 > 0:35:50He suggested they should remove all the carbon
0:35:50 > 0:35:52and then add 1% back in.
0:35:54 > 0:35:55It worked.
0:35:59 > 0:36:04For the first time we could mass-produce high-quality steel.
0:36:04 > 0:36:06We now had a metal that was strong enough
0:36:06 > 0:36:09and tough enough to fulfil our ambitions.
0:36:13 > 0:36:16The breakthrough made Bessemer's name,
0:36:16 > 0:36:20but he had to be forced to acknowledge the part Mushet had played.
0:36:22 > 0:36:25In the end, Bessemer had to agree to pay him
0:36:25 > 0:36:28£300 a year for the rest of his life.
0:36:30 > 0:36:36With mass-produced steel we'd cracked the problem of strength.
0:36:36 > 0:36:3890% of the metal we make today is steel.
0:36:41 > 0:36:46It's allowed as to travel across the globe by rail...
0:36:46 > 0:36:48..by road...
0:36:48 > 0:36:50..and by sea.
0:36:50 > 0:36:56Strong, reliable steel enabled us to build great cities.
0:36:56 > 0:36:59The construction industry would be nowhere without steel,
0:36:59 > 0:37:04and the destruction industry benefited just as much.
0:37:07 > 0:37:11But steel was not the answer to all our ambitions.
0:37:11 > 0:37:15Aluminium would be the metal of the next century.
0:37:16 > 0:37:21The century when the secret inner world of metals would finally be revealed.
0:37:22 > 0:37:26The thing about metals is they all look roughly the same.
0:37:26 > 0:37:30But they're not the same. This is steel and this is aluminium.
0:37:33 > 0:37:36Aluminium is three times lighter than steel.
0:37:38 > 0:37:43Here was the perfect metal to take us into the next age
0:37:43 > 0:37:45the age of flight.
0:37:45 > 0:37:50Except for one thing aluminium is just not strong enough.
0:37:52 > 0:37:58Scientists around the world began to look for ways to make aluminium stronger.
0:37:59 > 0:38:02Among them was the German metallurgist, Alfred Wilm.
0:38:04 > 0:38:10Wilm knew that our ancestors had strengthened copper by mixing it with tin,
0:38:10 > 0:38:15and what made steel strong was having the right combination of iron and carbon.
0:38:15 > 0:38:20So, he set about mixing aluminium with other metals.
0:38:22 > 0:38:25He finally ended up with an alloy of aluminium, copper,
0:38:25 > 0:38:28manganese and magnesium.
0:38:28 > 0:38:29He named it duralumin.
0:38:31 > 0:38:34And then he thought, when you want to make really hard steel,
0:38:34 > 0:38:37what you do is you quench it, so he took those alloys
0:38:37 > 0:38:41and he put them in a furnace and he quenched them.
0:38:41 > 0:38:42Here it is...
0:38:44 > 0:38:47..and I'm going to quench it.
0:38:50 > 0:38:56Now, once he'd quenched the alloys the moment of truth came.
0:38:57 > 0:39:01Would it be as strong as steel?
0:39:05 > 0:39:06No.
0:39:07 > 0:39:12And this happened time and time and time and time again.
0:39:13 > 0:39:16Until he could take the disappointment no more.
0:39:16 > 0:39:19He stormed out of his lab and...
0:39:19 > 0:39:22..went boating for a few days.
0:39:24 > 0:39:28But while he was messing about on the river,
0:39:28 > 0:39:31something remarkable happened.
0:39:31 > 0:39:36Something that Wilm had neither planned nor even imagined possible.
0:39:36 > 0:39:38This is the same alloy.
0:39:38 > 0:39:42The only differences is it's a week later now, and watch this.
0:39:45 > 0:39:47It's much, much stronger.
0:39:49 > 0:39:54'And this is what Wilm found when he returned from his boating trip.
0:39:54 > 0:39:58'Without Wilm lifting a finger, his alloy had transformed itself
0:39:58 > 0:40:02'from a weak, bendy substance into a strong, rigid one.
0:40:03 > 0:40:06'It was almost as though the lump of inert metal
0:40:06 > 0:40:12'he had left behind was a living thing that had changed over time.
0:40:12 > 0:40:14'It had grown harder as it aged.'
0:40:16 > 0:40:19What Wilm had discovered was something called age hardening.
0:40:19 > 0:40:21Let me show you how it works.
0:40:21 > 0:40:23So, if this is a crystal of aluminium,
0:40:23 > 0:40:26we know that's really soft.
0:40:26 > 0:40:29What we need is something that's going to make it stronger.
0:40:29 > 0:40:32Actually, he'd found an alloy which, when you leave it over time,
0:40:32 > 0:40:37tiny little crystals grow inside the aluminium crystals.
0:40:37 > 0:40:42They emerge out of a kind of atomistic mist, and it's those
0:40:42 > 0:40:47that harden the crystal, they make it stronger, they reinforce it.
0:40:52 > 0:40:55As new crystals grow, they interfere with the lattice,
0:40:55 > 0:41:00and the aluminium alloy's ability to shuffle atoms and change shape.
0:41:01 > 0:41:03This makes it harder and stronger.
0:41:08 > 0:41:12Wilm had solved the problem of how to make aluminium stronger.
0:41:13 > 0:41:18And he had also revealed metals to be mutable, almost living materials.
0:41:19 > 0:41:25So many of the great discoveries of science come by happy accident.
0:41:25 > 0:41:30From Alfred Wilm's despair came a new understanding of metals,
0:41:30 > 0:41:34an understanding that would finally allow us to conquer the skies.
0:41:37 > 0:41:44His alloy, duralumin, was used to make the fuselage of the Spitfire -
0:41:44 > 0:41:49the only Allied aircraft to remain a front line fighter throughout the Second World War.
0:41:51 > 0:41:55War forced the pace, with new and better alloys.
0:41:55 > 0:41:58Peacetime brought the desire for passenger flight.
0:41:59 > 0:42:03We were about to push metals harder than ever before.
0:42:08 > 0:42:13In great secrecy, the De Havilland company here in Hertfordshire
0:42:13 > 0:42:19embarked on an ambitious plan to build the world's first commercial jet aircraft,
0:42:19 > 0:42:23to tame and harness changeable, mutable metal
0:42:23 > 0:42:27and build a plane strong and reliable enough
0:42:27 > 0:42:31to soar twice as high as man had gone before.
0:42:34 > 0:42:37The plane was the ultimate in modern technology.
0:42:37 > 0:42:41It went higher and faster, and boasted a pressurised cabin
0:42:41 > 0:42:45for the comfort of the jet age passengers and crew.
0:42:45 > 0:42:49It was also the most tested aircraft of its time.
0:42:53 > 0:42:58Mike Ramsden was one of the test engineers on this,
0:42:58 > 0:43:00'the De Havilland Comet.'
0:43:00 > 0:43:03Can you remember the moment when you stood on an airfield
0:43:03 > 0:43:07looking at this Comet taking off, the comet you'd tested?
0:43:07 > 0:43:09It was...
0:43:09 > 0:43:14It was like watching something from outer space, it was so...
0:43:14 > 0:43:18..new, and it sounds corny, doesn't it?
0:43:18 > 0:43:21But there was nothing else like it in the world.
0:43:21 > 0:43:24When the crew were up at double the height
0:43:24 > 0:43:27and double the speed of propeller airliners,
0:43:27 > 0:43:30they just couldn't believe it,
0:43:30 > 0:43:33being able to see both sides of the Channel at the same time.
0:43:33 > 0:43:36And flying high, you had pressurised the cabin.
0:43:37 > 0:43:41Yes, this was a very big engineering challenge.
0:43:41 > 0:43:43To pressurise the fuselage
0:43:43 > 0:43:48so that human beings could survive at that height.
0:43:58 > 0:44:01It was the way to go, it was the way to fly.
0:44:01 > 0:44:03It was the way to arrive.
0:44:07 > 0:44:11It seemed that a golden age of air travel had dawned.
0:44:12 > 0:44:15But it was about to turn to disaster.
0:44:18 > 0:44:22A year to the day after the first passenger flight,
0:44:22 > 0:44:27a Comet disintegrated in midair, killing everybody on board.
0:44:28 > 0:44:32Within months, two more Comets had crashed into the Mediterranean.
0:44:32 > 0:44:34The entire fleet was grounded.
0:44:36 > 0:44:40There was something going on at the heart of metal we didn't understand.
0:44:42 > 0:44:44Did the whole staff, you and all your workmates,
0:44:44 > 0:44:47did you all feel responsible?
0:44:47 > 0:44:52Did we feel guilty, you mean, of killing 100 people?
0:44:52 > 0:44:54Yes, is the short answer.
0:45:05 > 0:45:07Finding the cause was now the priority for Mike
0:45:07 > 0:45:09and his colleagues.
0:45:09 > 0:45:13They knew metal was a mutable material,
0:45:13 > 0:45:17that it could suffer from a damaging phenomenon called metal fatigue.
0:45:17 > 0:45:20They had tested extensively for this.
0:45:22 > 0:45:25But what they couldn't predict were the effects
0:45:25 > 0:45:28of this extreme new environment and the pressurising
0:45:28 > 0:45:32and de-pressurising of the cabin needed for high altitude flight.
0:45:36 > 0:45:38The real problem was a combination of factors,
0:45:38 > 0:45:41one of which was that this aircraft had to go higher
0:45:41 > 0:45:46than ever before, up five miles high, which caused a compression
0:45:46 > 0:45:48and decompression of the fuselage,
0:45:48 > 0:45:51so you have it almost breathing in and out, in and out,
0:45:51 > 0:45:53every time it takes off and lands.
0:45:55 > 0:45:58The stress of constant pressurisation and de-pressurisation
0:45:58 > 0:46:00eventually tolled on this aeroplane.
0:46:03 > 0:46:05Metal will break if you bend it often enough.
0:46:05 > 0:46:09In the Comet's fuselage, tiny fatigue cracks appeared.
0:46:09 > 0:46:13What began as a very small fracture close to a window
0:46:13 > 0:46:16spread in to a catastrophic crack.
0:46:16 > 0:46:18The whole aircraft came apart mid-flight.
0:46:18 > 0:46:21The cause was a combination of metal fatigue
0:46:21 > 0:46:24and concentrations of stress within the fuselage.
0:46:26 > 0:46:30It's a weird quirk of fate that these windows were square
0:46:30 > 0:46:32because that's exactly the wrong shape
0:46:32 > 0:46:35if you want to minimise the concentration of stress.
0:46:35 > 0:46:39So at the corners the stress is all concentrated
0:46:39 > 0:46:41and started forming little cracks,
0:46:41 > 0:46:44it was those that were the big problem.
0:46:44 > 0:46:48Today we know that you mustn't have square windows
0:46:48 > 0:46:50in these kind of pressure structures.
0:46:50 > 0:46:54If you look at any aircraft today, you'll never see a square window.
0:46:57 > 0:46:59Comet changed everything.
0:46:59 > 0:47:01New regulations would make sure that metal was replaced
0:47:01 > 0:47:03before it became fatigued.
0:47:03 > 0:47:07But the most important lesson we learnt was just how little we knew.
0:47:09 > 0:47:12Extreme conditions were causing extreme reactions
0:47:12 > 0:47:15inside the metal that we didn't understand.
0:47:15 > 0:47:18We desperately needed to see what was happening
0:47:18 > 0:47:22deep inside the metal crystal.
0:47:25 > 0:47:27One young scientist was about to make a breakthrough
0:47:27 > 0:47:30and I know him really well because a few decades later
0:47:30 > 0:47:33he was one of my lecturers here at Oxford University,
0:47:33 > 0:47:35Professor Sir Peter Hirsch.
0:47:40 > 0:47:45Hirsch's team was one of the first to take thin foils of metal
0:47:45 > 0:47:48and look at them under a brand new kind of microscope,
0:47:48 > 0:47:51a transmission electron microscope,
0:47:51 > 0:47:54which increased magnification by tens of thousands.
0:47:54 > 0:47:58Hirsch would finally see inside the metal crystal
0:47:58 > 0:48:02and what he found would send shock waves around the world of material science.
0:48:05 > 0:48:07Meeting up with Professor Hirsch again,
0:48:07 > 0:48:11he explained that in the 1950s there were theories
0:48:11 > 0:48:15about why metals behaved as they did, but still no proof.
0:48:17 > 0:48:21What was really needed was an experimental technique
0:48:21 > 0:48:26which was universally applicable whereby you could see inside metals.
0:48:29 > 0:48:31And that's what Hirsch discovered.
0:48:31 > 0:48:34This is the film he took of his original experiments.
0:48:34 > 0:48:40He saw for the first time deep inside the metal crystal,
0:48:40 > 0:48:43where, incredibly, the metal looked like it was alive.
0:48:43 > 0:48:47Those moving little lines and loops are the Mexican waves of atoms
0:48:47 > 0:48:50shuffling across the metal crystal.
0:48:50 > 0:48:53They're changing the shape of the crystal.
0:48:53 > 0:48:56Suddenly everything fell into place.
0:48:56 > 0:49:00The technique revealed a new micro-world, if you like,
0:49:00 > 0:49:02inside a metal.
0:49:02 > 0:49:06You suddenly saw the inside of a metal
0:49:06 > 0:49:09and all sorts of things were revealed.
0:49:09 > 0:49:15It was very, very exciting.
0:49:15 > 0:49:17We were now in a position to prove
0:49:17 > 0:49:20what had previously only been guessed at...
0:49:20 > 0:49:23That metals were dynamic crystals,
0:49:23 > 0:49:25that these ripples were caused by atoms
0:49:25 > 0:49:28shuffling within the crystal, changing the metal's shape.
0:49:31 > 0:49:34This explained what we'd known for centuries, but never fully understood...
0:49:34 > 0:49:37Why metal would change shape
0:49:37 > 0:49:41rather than crack when it was hit with a hammer.
0:49:41 > 0:49:46And also why it became stronger when it was alloyed.
0:49:46 > 0:49:49It showed that designing the internal architecture of metal
0:49:49 > 0:49:51was the key to progress.
0:49:55 > 0:50:01Microscopy finally allowed us to master the micro-world of metals.
0:50:03 > 0:50:06Hirsch's breakthrough reignited our passion and belief for metals.
0:50:06 > 0:50:08We could start to design our own metals,
0:50:08 > 0:50:11and there was a huge flowering of metallurgy.
0:50:11 > 0:50:14There seemed to be no problem we couldn't solve.
0:50:14 > 0:50:18'And we were facing another.
0:50:18 > 0:50:21'How to get a metal to work in the most extreme environment on earth.
0:50:21 > 0:50:24'A jet engine.'
0:50:24 > 0:50:26Let me show you what I mean.
0:50:26 > 0:50:28Inside jet engines,
0:50:28 > 0:50:30is an incredibly difficult place for metals to be.
0:50:30 > 0:50:32Extremely hot temperatures.
0:50:32 > 0:50:35Extremely high stress they had to put up with.
0:50:35 > 0:50:37So they had to design a new alloy
0:50:37 > 0:50:39that could cope with this environment.
0:50:39 > 0:50:41And it was called "superalloy".
0:50:41 > 0:50:43So-called because it was so super.
0:50:43 > 0:50:45Here's a bit of it here.
0:50:45 > 0:50:47I'm going to pit it against our old friend steel,
0:50:47 > 0:50:49who, of course, we know and love.
0:50:49 > 0:50:52I'm going to hang weights off these two wires.
0:50:52 > 0:50:53It's the same weight, in both cases,
0:50:53 > 0:50:57and they're the same thickness of wire.
0:50:57 > 0:50:59So, now they're under the same stress.
0:50:59 > 0:51:01Now, I'm going to make it harder for them,
0:51:01 > 0:51:05because they'll have to hold that up while under huge temperatures,
0:51:05 > 0:51:09which means me putting a blowtorch on them.
0:51:09 > 0:51:12OK, are you guys ready? Let's go.
0:51:17 > 0:51:20So, the steel wire succumbed within a few seconds.
0:51:20 > 0:51:24And that's only a fraction of the heat inside a jet engine.
0:51:27 > 0:51:31I could be here all day with the superalloy.
0:51:31 > 0:51:32This superalloy can take this.
0:51:34 > 0:51:37I know these metals all look the same, but inside this superalloy
0:51:37 > 0:51:39is the most-exquisite microstructure,
0:51:39 > 0:51:43that was designed for this purpose.
0:51:43 > 0:51:45To control the movement inside the metal,
0:51:45 > 0:51:49and make it unbelievably strong at high temperatures.
0:51:51 > 0:51:54'The cubes of material within the superalloy
0:51:54 > 0:51:56'are called "gamma prime crystals".
0:51:56 > 0:51:58'They sit within the alloy,
0:51:58 > 0:52:00'affecting its ability to change shape.
0:52:01 > 0:52:03'Which makes it incredibly strong,
0:52:03 > 0:52:06'even at temperatures close to its melting point.'
0:52:09 > 0:52:11That's pretty impressive,
0:52:11 > 0:52:13and, as the jet age progressed,
0:52:13 > 0:52:16scientists and engineers pushed the technology,
0:52:16 > 0:52:19to create more and more powerful engines.
0:52:22 > 0:52:25'Superalloys were some of the strongest metals
0:52:25 > 0:52:26'we had ever created.
0:52:26 > 0:52:29'But the 21st century jet engine
0:52:29 > 0:52:30'would push them to their limit.
0:52:30 > 0:52:33'In this extreme environment,
0:52:33 > 0:52:36'even superalloys will change shape.'
0:52:36 > 0:52:40One of the things we love about metals is their malleability.
0:52:40 > 0:52:42When it's red hot, it behaves like plastic.
0:52:42 > 0:52:45You can make it into whatever shape you want.
0:52:45 > 0:52:49This is wonderful stuff to make an engine out of.
0:52:49 > 0:52:52But the problem is, when you're making an engine
0:52:52 > 0:52:54that needs to be operating at temperatures
0:52:54 > 0:52:56that are themselves red hot,
0:52:56 > 0:52:59deep inside the engine, you've got engine parts
0:52:59 > 0:53:01that really musn't change shape.
0:53:01 > 0:53:06'These turbine blades operate at 1,700 degrees centigrade,
0:53:06 > 0:53:08'and 10,000 RPM.
0:53:08 > 0:53:09'If working in those conditions
0:53:09 > 0:53:13'made them lengthen, even a tiny bit,
0:53:13 > 0:53:15' a phenomenon known as "creep",
0:53:15 > 0:53:18'catastrophe would follow.'
0:53:18 > 0:53:21These engines are designed with the precision of a watchmaker.
0:53:21 > 0:53:24Here, at the back of the engine, you can see the turbine blades rotating
0:53:24 > 0:53:26within the casing.
0:53:26 > 0:53:29If there's any creep in those turbine blades,
0:53:29 > 0:53:32they'll hit the casing, and the whole thing will seize up.
0:53:32 > 0:53:33And that must not happen.
0:53:33 > 0:53:37Unlike with a car, there's no hard shoulder in the sky.
0:53:40 > 0:53:43'Creep can affect any metal.
0:53:43 > 0:53:45'In extreme environments,
0:53:45 > 0:53:47'the boundaries where crystals join
0:53:47 > 0:53:52'can become routes that atoms travel along, elongating the crystals.'
0:53:54 > 0:53:58So, what can we do about creep?
0:53:58 > 0:54:00Metals are made of crystals,
0:54:00 > 0:54:04and if the crystal boundaries are the problem,
0:54:04 > 0:54:07we can't take all the crystals out.
0:54:07 > 0:54:10Or can we?
0:54:13 > 0:54:17'This is the Rolls-Royce turbine blade facility, in Derby.
0:54:17 > 0:54:21'An entire factory dedicated to making blades,
0:54:21 > 0:54:25'which work right at the heart of a 21st century jet engine.
0:54:27 > 0:54:30'Here, they're actually producing turbine blades
0:54:30 > 0:54:33'from a single metal crystal,
0:54:33 > 0:54:36'like a giant diamond of metal.
0:54:36 > 0:54:39'These blades are resistant to creep.
0:54:42 > 0:54:46'Paul Withey is a casting specialist at Rolls-Royce.'
0:54:46 > 0:54:49This is where we cast the single crystal turbine blades.
0:54:49 > 0:54:50This is the wax model of the blade.
0:54:50 > 0:54:53What actually do is, as part of the assembly process,
0:54:53 > 0:54:55we'll fit in the spiral onto the bottom of it,
0:54:55 > 0:54:58to allow us to grow a lot of crystals in at the bottom.
0:54:58 > 0:55:01One crystal is selected through a spiral,
0:55:01 > 0:55:03and made to grow through the whole of the rest of the blade.
0:55:03 > 0:55:07'This is astonishing stuff.
0:55:07 > 0:55:09'We've conquered creep,
0:55:09 > 0:55:12'by growing our own metal.
0:55:12 > 0:55:14'The crystal boundaries that cause creep
0:55:14 > 0:55:17'are prevented by the spiral tube,
0:55:17 > 0:55:20'which stops all but one metal crystal getting through,
0:55:20 > 0:55:25'allowing that single crystal to grow into the whole mould.'
0:55:25 > 0:55:28It's amazing that one of our earliest activities with metal
0:55:28 > 0:55:30was to cast it.
0:55:30 > 0:55:32It's really where we came from, as a civilisation.
0:55:32 > 0:55:35Here we are, one of the most sophisticated pieces of metallurgy
0:55:35 > 0:55:38you can possibly do, and it's casting again.
0:55:38 > 0:55:41Yes. And it's actually using the same process that was used
0:55:41 > 0:55:45over 5,000 years ago, to make art and religious artefacts,
0:55:45 > 0:55:47and here today is being used to make
0:55:47 > 0:55:51some of the most hi-tech engineering components that you can find.
0:56:00 > 0:56:03'In this age of single crystal turbine blades,
0:56:03 > 0:56:06'it seems that we've finally understood how metals work,
0:56:06 > 0:56:09'and how to make them work for us.
0:56:11 > 0:56:13'Paul, and the engineers at Rolls-Royce,
0:56:13 > 0:56:16'are all upbeat about the future of metals.
0:56:16 > 0:56:18'But not everybody agrees.
0:56:22 > 0:56:24'Some of my colleagues in material science
0:56:24 > 0:56:27'are beginning to think we've outgrown metals.
0:56:27 > 0:56:29'We've mastered them,
0:56:29 > 0:56:31'and now we should move on to other materials.
0:56:31 > 0:56:34'But should we dismiss them so easily?'
0:56:34 > 0:56:37Metals are in everything around us.
0:56:37 > 0:56:40The electricity that made that kettle boil
0:56:40 > 0:56:43came down a wire, and that wire itself is made of metal.
0:56:43 > 0:56:45Here's some.
0:56:45 > 0:56:46It's copper.
0:56:46 > 0:56:49So, the Copper Age is embedded in our homes.
0:56:49 > 0:56:51It delivers all our electricity to us.
0:56:51 > 0:56:55Then, the Bronze Age is still here,
0:56:55 > 0:56:56for anyone who likes sculpture.
0:56:56 > 0:56:59Beautiful, aesthetic material.
0:56:59 > 0:57:02The Iron Age is here,
0:57:02 > 0:57:04and steel?
0:57:04 > 0:57:08We spent thousands of years honing this material to be strong, tough,
0:57:08 > 0:57:10and ultra-sharp.
0:57:10 > 0:57:12Let's not forget the modern metals.
0:57:12 > 0:57:14We fly around with aluminium,
0:57:14 > 0:57:17but it's in our kitchens, too,
0:57:17 > 0:57:19in this lovely, wafer-thin metal,
0:57:19 > 0:57:22which is just extraordinarily versatile.
0:57:24 > 0:57:27But there's something a little sad about the history of metals.
0:57:27 > 0:57:29Each one starts out as a revolution.
0:57:29 > 0:57:34But, after a while, they recede, and we take them for granted.
0:57:34 > 0:57:36But I really don't think we should.
0:57:36 > 0:57:39If it wasn't for metals, we'd still be in the Stone Age.
0:57:39 > 0:57:44Everything around us is shaped by metals. Everything.
0:57:44 > 0:57:49It's that step-by-step understanding of the internal structure of metals,
0:57:49 > 0:57:51the secret world of the metal crystal,
0:57:51 > 0:57:54that's been a huge intellectual achievement.
0:57:54 > 0:57:57Metals have driven civilisation forward.
0:57:57 > 0:58:01And, in doing so, they've defined who we are as humans.
0:58:01 > 0:58:04And that's something we should be VERY proud of.
0:58:26 > 0:58:29Subtitles by Red Bee Media Ltd