Michael Mosley explores how history shaped science. Here, he looks at how atomic theories and the strange concepts of quantum physics came into being.
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There are some great questions that have intrigued
and haunted us since the dawn of humanity.
What is out there?
How did we get here?
What is the world made of?
The story of our search to answer those questions is the story of science.
Of all human endeavours, science has had the greatest impact
on our lives - on how we see the world, on how we see ourselves.
Its ideas, its achievements, its results are all around us.
So how did we arrive at the modern world?
Well, that is more surprising and more human than you might think.
The history of science is often told
as a series of eureka moments,
the ultimate triumph of the rational mind.
But the truth is that power and passion,
rivalry and sheer blind chance have played equally significant parts.
In this series, I'll be offering a different view of how science happens.
It's been shaped as much by what's outside the laboratory as inside.
This is the story of how history made science
and science made history. And how the ideas that were generated changed our world.
It is a tale of power, proof and passion.
This time, delving deep to find order and beauty.
What is the world made of?
Beneath the surface, our world is stranger than we can possibly imagine.
Standing here, it certainly feels as if I am standing on a solid surface.
But this is an illusion, however convincing.
Nothing is really solid.
And you and I? Well, we consist almost entirely of empty space.
If you took the entire population of the world, all six billion of us,
and removed that empty space, then we could be squeezed into a cube smaller than that.
And it gets stranger.
Mobile phones and other electronic devices which we rely on.
Well, they rely on particles that, by any normal definition, simply don't exist.
These insights all come from our attempts to find out what the world is made of.
Over the millennia, our understanding has moved ever deeper,
revealing new layers that make up the material world.
It may seem like an academic, esoteric quest.
It's anything but.
Every time we've gone down a layer and achieved a deeper understanding of matter,
that knowledge has spawned new technologies and huge amounts of wealth and power.
The first people who systematically tried to unlock the secrets
of what the world is made of, and to alter it, were the alchemists.
They flourished in the late Middle Ages,
working in secret, protecting their knowledge with codes and ciphers.
It's easy to dismiss the alchemists as deluded mystics,
forever trying to turn lead into gold.
Or, perhaps, conmen,
who used simple chemistry to impress the gullible.
But the roots of a scientific investigation
of what the world is made of, lie in their secret laboratories.
The alchemists' beliefs about matter were largely based on ideas
that had come down from the ancient Greeks, who believed that,
well, pretty well everything around you was made up of earth, fire, air and water.
Theirs was a system of beguiling simplicity.
Everything in the world was a combination of just four idealised elements...
Now, they were completely wrong in that, but the central principle, that you can explain a complex world
by just simple building blocks or elements, that was important.
But what really interests me about the alchemists is their practical abilities.
I want to try and repeat a bizarre experiment,
performed by one of the last of the alchemists, a German called Hennig Brand.
Brand believed he was on the brink of discovering the philosopher's stone,
a substance that reputedly turned base metals into gold.
He thought he could find it in human urine.
-How long have you had this?
-Well, we've not had it...
Whoa! Jeez, yeah, no, I got a good waft of that one!
-But it gets worse.
I suspect Hennig Brand was not tremendously popular with the girls.
Having boiled down our starting material, we will then,
sort of, reduce it to a solid.
Finally, we'll distil it and see if we can get something interesting.
Let me try and bring you into the mindset of the alchemists.
They believed that everything on Earth was in some way alive - and that included metals.
Metals would grow in the earth like seeds and,
like the human body decomposing, they would also decompose. They would rust.
But metals could also be improved.
They could be made better. They could be purified.
And if that happened, they became gold, the purest metal of all.
It was the legendary philosopher's stone
that the alchemists believed could bring about this transformation.
Here it is. Here it is. We've been...
It looks absolutely putrid, I have to say.
Well, I can tell you that, even as a chemist, and I've smelled
-a lot of stuff, this is seriously, seriously unpleasant.
So we've boiled down about half a litre of urine
to this and you can see that it's starting to get a bit pasty.
There's all sort of white solids.
Oh, God! Oh, God that is bad!
That is really bad! Oh.
But what he would have had to do was to transfer it into this retort.
So we're going to pour it in through the top.
I'm just going to run it down this glass rod.
And the next thing presumably is extreme heat?
And now, the trial by fire, if you will.
It involved great technical skill.
Controlling temperature, making the furnace and glass retorts.
But his strong constitution and persistence produced strange results.
So what had he extracted from the urine?
I can show you and, if you look, we've actually got it stored
under water, much as Brand probably would have stored it.
I think what we should do is see what happens when it burns.
Oh! Whoo! Whoo! Whoo!
-You can see the plumes of white smoke.
-Good Lord! Am I OK to touch?
You can, in fact, lift it, yes.
-It's beautiful and I think terrifying at the same time.
It is phantasmagorical, isn't it?
I mean it really is unearthly.
It's magic of the highest order.
Brand, of course, never found the philosopher's stone.
His discovery was named "Giver of Light", or phosphorous.
It became rather important.
It was later used to make the match.
It's tempting to think of the alchemists as a bunch of mystics who made a few lucky discoveries,
but if you look at the equipment behind there, it tells a very different story.
You have scales, oven, retort -
equipment you would find in any modern chemistry lab.
I have absolutely no doubt that the quest to understand what the world
was made of was hugely helped by the work done down the years by the alchemists.
But by Brand's time, the alchemists were on the wane.
And the ancient idea of a world made up of just four forms of matter was about to be demolished.
As Europe moved out of the Middle Ages, new forces started to shape science.
Powerful, absolute monarchies ruled the continent.
They were hungry for weapons as they battled for supremacy.
That led to a strategic interest in more and better metals.
The hunger for metals was insatiable and the dirty business
of getting metal ores out from deep underground became ever more important.
Mines were one of the places where challenges to the age-old beliefs started to emerge.
Air had long been considered a single indivisible substance,
a basic building block of the world.
But as Europe industrialised, it became increasingly obvious that this was far from the truth.
People realised, from personal experience,
that there were lots of different airs, with very different properties.
There was bad air, which killed men down mines and mysteriously extinguished candles.
There was fire damp, which ignited below ground without warning.
And the wonderfully-titled Phlogisticated Air, produced by combustion.
All of this raised questions.
What were these airs?
How many were there?
Across Europe, experimenters went looking for answers.
In Yorkshire, the challenge was taken up by the natural philosopher Joseph Priestley...
..a man who set out to probe the hidden mysteries of nature.
Joseph Priestley was a precocious youth.
By the age of four, he could recite perfectly
all 107 questions and answers in the Westminster Shorter Catechism.
He joined the church, but he also became a brilliant experimenter.
He was looking for God, not just in the Bible, but in the natural world.
Priestley was among the foremost air experimenters of the day.
And it was these new airs or gases that would help create a new vision of what the world is made of.
Priestley set out to study airs by heating different substances...
..including an old alchemist favourite, red calx.
I love the way the colour changes, as it's going from a sort of orange to a very rich red.
Priestley heated it to a high temperature and the orange powder transformed into a shiny metal.
And with a new piece of equipment, the pneumatic trough, he collected a new air.
OK, and here it is.
A precious container full of mystery gas. Now, to test it.
Turn it upside down
-and then quickly remove the lid.
-And it reinflames...
Goes out again and then it burns.
He described what he'd collected as "good air".
And he was enchanted by its fiery properties.
It turned out to be the most important of the new airs yet discovered.
In 1774, Priestley went on a fateful trip to Paris.
Now, he could never ordinarily have afforded such a thing, but on this occasion he went as the guest of a
British aristocrat and he took with him knowledge of his new discovery.
When he arrived in Paris, Priestley was invited to dine
with the golden couple of French experimental science,
Antoine and Marie-Anne Lavoisier.
They had created the best-equipped private laboratory in Europe,
dedicated to measurement and precision.
He had a vaulting ambition to define a new science - of chemistry.
His contribution to how we live now is arguably as great as that of Newton or Darwin.
When he was a young man, Lavoisier said, "I am avid for glory".
And he achieved that, though at huge personal cost.
They couldn't have been less alike, the Paris sophisticate and the working-class Yorkshire man.
I imagine that Priestley was rather overwhelmed by the occasion,
by the magnificent setting, the fine wines, by Antoine Lavoisier and by his brilliant guests.
As he later wrote to his wife, "most of the philosophical people of the city were present".
And, as evening developed, the conversation turned to the subject of airs.
Priestley soon told them about his recent discovery, an air with fiery properties,
and then he also told them exactly how to make it.
Across the table, Lavoisier listened intently.
As Priestley later noted, "everyone round that table expressed great surprise".
Armed with Priestley's knowledge, Lavoisier set off to repeat the experiment.
And was soon boasting of HIS discovery,
the same air, but with a new name.
Lavoisier called it "oxygen".
It is the gas of life.
But what Lavoisier did next is, I think, a defining moment in the story of science.
He decided to run the Priestley experiment in reverse,
the gas and the shiny metal recombined to form red calx.
Now, the really significant bit...
He found it weighed exactly the same as before.
This was to become a fundamental principle of modern chemistry.
This was momentous.
Lavoisier had discovered that everything balances.
You can take a substance, split it down into simple elements
then recombine those elements and you get back to where you started.
For me, this marks the beginning of a modern understanding of matter, of how the world is really made.
The science of chemistry now emerged.
Out of connections.
Between the practical skills of the alchemists.
The discovery of new gases.
And a dedication to precise measurement.
The new chemistry would help create a new vision of what the world is made of.
Meanwhile, outside the laboratories of the rich, science was developing
a taste for the spectacular, powered by the new interest in airs.
We're about to re-enact a very important moment in the history of science.
There should be flames, shouts, screams and,
obviously, this is why we're all wearing funny costumes.
In the small French town of Annonay, descendents of a famous family of papermakers, the Montgolfiers,
recreate the time when an ancient dream of taking to the skies became a reality.
It's incredibly hot and smoky under there.
The Montgolfier brothers, when they originally did this experiment, they had no idea about the theory.
They were practical men who wanted to make money and they thought what was happening to straw,
producing something called Montgolfier Gas, which contains levity, which is what lifts it up.
And now we're cooking! Whoa! This is... This is seriously hot.
That was a sight.
It was great fun. We know about flight, but imagine you had never seen anything fly like that before.
It would blow your mind.
The first balloon, made entirely out of paper, soared a mile into the heavens.
The race was now on to carry a man into the skies.
And in November 1783, two brave volunteers took to the air.
The first humans to look down at the surface of their own planet.
But very soon, the hot air balloon had a rival,
backed by the scientific establishment of France.
Just ten days later, another balloon rose.
This was driven by a newly-discovered gas, called inflammable air.
It was 13 times lighter than normal air and considerably less dangerous than using a blazing pile of straw.
It had huge lifting power.
This was science as public event.
Half the city of Paris turned out to watch.
400,000 people, all staring upwards in amazement.
But its success laid down a challenge to the chemist.
How could they make enough of this new gas to fill the skies with floating aeronauts?
It was a challenge picked up by the champion of the new chemistry...
Ever the experimenter, his solution was daring, to find a way to break apart a fundamental substance...
-Nice to see you again.
-Good to see you, Michael.
I love this. I'm very impressed
because I've got a drawing here of what Lavoisier's original apparatus looked like
and I think that's pretty damned close.
This apparatus was constructed to test Lavoisier's idea
that water could be split into two very different gases,
oxygen and the new inflammable air.
-So what we have is a system to essentially make rust in a great hurry.
So we have iron in the centre and then we have water
which is trickling down, and by raising the temperature,
what we do is, we essentially speed up the reaction.
Right, so the oxygen in the water is going to bind to the iron?
Absolutely. The iron is essentially the oxygen getter in this system.
If I let a bit of water in at this end,
that's going to get very hot and you can see
with trained steam and that's why we have a bit of pressure behind it.
-But it's now going to drain through and in the centre it should be reacting with the iron.
-We may be able to see bubbles down the far end.
-We've got bubbles.
-Congratulations. Well done!
I'm very impressed.
And those bubbles cannot be steam.
-Because the steam would be condensed here in the copper coil
and so that must be some, let's call it non-condensable gas.
But is it inflammable air?
We're getting anxious now, aren't we?
Well, we're ready.
We're going to put the splint in there.
And it was definitely hydrogen and it worked.
-It was in fact that pop sound...
..that you do get when hydrogen ignites. There's no question.
That was inflammable air as it was called in the 18th century.
Lavoisier's success encouraged Napoleon
to create a military balloon corps powered by hydrogen gas.
These two gases that make up water, hydrogen and oxygen,
were part of Lavoisier's bold new vision
of what the world is made of...
Elements. 33 in all.
His list included the newly discovered gases,
but he didn't get it entirely right.
He also included heat and light.
It was a tentative new list of the building blocks of matter.
Lavoisier's work coincided, tragically for him, with the upheaval of the French Revolution.
He made money from collecting taxes. He was a hated tax farmer.
Lavoisier must have realised that he was vulnerable.
A member of the revolutionary government had denounced former tax farmers like him
as leeches on the people, but he chose not to flee.
Here in La Place de la Concorde,
Lavoisier was put to death.
This was more than an individual tragedy.
As one of Lavoisier's colleagues put it,
it took just an instant to sever his head and over 100 years would not suffice to produce another like it.
We have now gone down a layer in our understanding of what the world is made of...
To a world of elements.
Each of them considered an unbreakable building block of matter
and this new understanding would begin to release great power.
Our journey now moves to the sublime landscape of the Lake District.
At the end of the 18th Century this was home to William Wordsworth, one of the great poets of the day.
Wordsworth was a leading member of a movement called Romanticism.
They prized feelings and intuition over cold hard logic.
Romantic science sounds like a contradiction in terms
but, as we'll discover, the romantic poets had a surprisingly profound effect on the story of science.
That might sound unlikely,
but the link can be found here in Wordsworth's Dove Cottage.
So this is, of course, William Wordsworth and over here we've got another of the romantic poets.
This is Samuel Taylor Coleridge, Rime Of The Ancient Mariner and Kubla Khan.
But the man I've really come to see is him,
Humphry Davy, one of Britain's greatest chemists.
So what's he doing here?
Well, Humphry Davy and the romantic poets shared an interest in poetry,
in the power of nature and in a certain mood-altering substance.
They called it laughing gas and Davy generously shared it with his romantic friends.
But the connections went much deeper.
Isn't it gorgeous?
You can see why Davy loved this place
and he shared with the romantic poets a belief that if only you
could understand the laws of nature and live in harmony with them, then the world would be a better place.
Poets and men of science stood in awe
of the hidden powers contained within nature.
They just had different ways of showing it.
And in 1801, Davy's social connections landed him a post at the Royal Institution in London.
Here he was able to carry out research and give public lectures.
His youthful glamour and taste for the spectacular made him an immediate success.
-You might need that.
-Ready to perform, then?
Show time! As I'm sure Humphry Davy once said.
'Dr Peter Wothers is helping to recreate the extravaganza that Davy brought here 200 years ago.'
-Carefully add a drop.
-OK. Can we...
See what happens to your sheep.
There would have been an enthusiastic crowd drawn to these wonderful exhibitions.
Somewhere over there, some ardent young women drawn by his charisma.
Over there you'd probably have seen Samuel Coleridge who was drawn, he said, to collect new metaphors.
And sprinkled throughout the crowd, a new breed of entrepreneur and factory owner who had come here
to collect valuable chemical information.
Humphry Davy had an instinctive understanding
of how spectacle and showmanship could be used to establish science as a powerful force in society,
controlled by a new breed of experts, men like him.
He thrilled his audience with his mastery of one of the wonders of the age...
Is this going to be dangerous?
Potentially, yes. It's very unpleasant material.
OK. I'll button up well, then!
Davy heated an unassuming white powder called potash
to a molten state and then passed electricity through it.
And did Davy have any idea what he was going to get when he did this experiment?
-I don't think he did, no.
-He just did it for a laugh.
Electricity broke the potash apart
..to reveal one of its building blocks.
A new element with a lilac glow.
He called it potassium.
The smoke you can see is actually potassium that's been formed
but is instantly reacting with the air.
This element was so volatile, so reactive,
that it disappeared almost as soon as it was isolated.
I'll just fish a chunk out.
-So this is potassium.
-I've never seen potassium. It looks like a metal, doesn't it?
-It looks like a metal,
but if we cut this it's a very soft metal.
You can see what potassium really looks like.
-This is pure potassium metal.
And you can see that this is already reacting
with the oxygen from the air.
So it's really impressive that Davy was able to do this 200 years ago.
It was quite a remarkable achievement to isolate this reactive metal.
Davy had a real knack for finding new elements.
Eight of them in less than two years.
-There we are.
-I was not expecting that.
But the significance of Davy's work lay in far more than new elements.
It extended to science itself and to popular culture.
There was the young author, Mary Shelley, who was inspired and disturbed by Davy's work.
It influenced her when she wrote Frankenstein, a novel which created a powerful and enduring image
of the mad experimenter who is dabbling in forces way beyond his control.
And then there was Davy's friend, the poet Samuel Taylor Coleridge.
Now he actually helped coin the name "scientist"
to describe what people like Davy did.
Alternatives included "science man",
but it was "scientist" that stuck.
But others in the audience had a more practical reaction.
Was chemistry useful? Was there money in it?
Chemistry was about to become a power in the world,
but the journey it took to get there was wonderfully unpredictable.
It starts in the tropics with a deadly problem that threatened the empires of the 19th century.
In Jamaica, once a British colony, I'm hoping to see how they tried to deal with it.
It's quite early morning. It's already unbelievably hot.
-We have a while to go, don't we?
How high are we? Do you know?
Oh, when you reach by Cinchona, you are 5,002 feet above sea level.
Right. Do you get mosquito up here?
-Is it too high?
-Oh, just a few.
On the upper slopes of the blue mountains grows a truly remarkable tree.
I like it here. It's nice.
It's just great to get off.
There are lots of unpleasant creatures in the tropics but the deadliest by far is the mosquito.
It has killed more people than anything else in history.
Now, it carries yellow fever, Dengue fever, but also malaria.
And in the 19th century, malaria was a huge problem for empire builders like the British.
Right. Is it this way?
-How big is it?
-About this high.
-OK. And how old is it?
The best defence against this disease was the bark of the Cinchona tree.
-You know the tree? You ever seen it before?
-It's that one there.
-Yes. This one here.
-Right, this is it.
-It's starts blooming there.
Yeah, this is probably the most amazing tree in history.
-It has relieved more human suffering than anything else.
-Right, and it's the bark we want, isn't it?
-I'm told it's fairly horrible. Have you tried it before?
-Yeah, man. Real bitter.
I've seen somebody, when I was doing medicine, I saw somebody die of malaria
so I have huge, huge appreciation for this.
Right, am I going to enjoy it?
Oh, God! Oh, God!
Oh, you were right!
That is really, really bitter. Just dries up your mouth, doesn't it?
On the grounds that something which is horrible is doing you good
then this must be extraordinarily good stuff.
Cinchona plantations were established all over the tropics.
But every year the empires of Europe needed hundreds of tons of the bark to combat malaria.
So governments looked to chemists to come up with a synthetic alternative.
In 1820, a couple of French chemists managed to isolate
the active ingredient in the bark and they called it quinine.
What people desperately wanted to do next was obviously produce an artificial version of quinine.
The problem was nobody had done anything as complex as that before.
The attempts to do so would open the world to chemistry on an industrial scale.
The challenge to make artificial quinine was taken up in a makeshift lab in London's East End...
in an attic room by young William Perkin.
And I like to think he found his inspiration round the corner, in his local music hall.
MUSIC: "Boiled Beef And Carrots"
Isn't it magnificent?
Now the theatre and in fact all of London would have been lit by gas lights.
And the gas was produced from coal.
Now, one of the rather nasty side products of that process was a black viscous substance called coal tar.
A certain Charles Mackintosh used this stuff and produced waterproof Macs.
But Perkin was about to make a discovery which was far, far more lucrative than that.
The chemicals he used to try and create quinine are highly toxic.
So I'm going to use substitutes to show what the process looked like.
Now from coal tar, other chemists had produced
a substance called aniline which contains similar amounts of carbon, hydrogen and nitrogen as quinine.
So this seemed like a pretty good place to start.
He mixed up his aniline with sulphuric acid
and also a substance called potassium dichromate
which is a sort of chemical mixer.
And then he left it all to sort of brew for a while.
What he found was black, gunky, really quite revolting.
I'm surprised he didn't chuck it away, but he didn't.
In his laboratory, at the top of his parents' house, he distilled, he mixed.
He eventually produced a very interesting little powder.
He had not discovered artificial quinine.
He had instead discovered something which had never been seen before and which he really wasn't expecting.
He had discovered the colour mauve!
He had created the first great synthetic dye and made the world a far more colourful place.
Perkin never did make quinine but he did create a fashion sensation.
The rich and famous loved his synthetic mauve.
This is really beautiful.
It's an antique Victorian dress.
Now, Perkin's mauve was more than simply a fashion statement.
The aniline dyes, which were used to colour this dress,
were the first to be produced on a truly industrial scale.
So strange as it may sound, this dress marks a significant moment in human history, when the synthetic
took over from the natural on a truly massive scale.
By the 1870s, Perkin's factory was making hundreds of tons of dye a year.
Adding Perkin's green and Britannia violet to his growing catalogue of vivid colours.
Perkin is rightly celebrated as the father of industrial chemistry
but the lead soon passed to Germany where industrial chemists worked out how to make ammonia,
which led to artificial fertilisers
which today sustain the global population.
But the journey that began in the tropics with the search for quinine
also led here...to the killing fields of the Great War.
Uniforms were coloured khaki with artificial dyes.
Explosives were produced by the same process used to make fertilisers.
It brought us the horrors of poison gas, chlorine.
A gas used in the dye industry that Perkin had pioneered.
The First World War has been described as the "Chemist's War".
Industrial chemistry became a force in world history,
the result of connections between the discovery of elements,
the growth of European empires
and the colour mauve.
But the search for what the world is made of was far from over.
In universities across the world, researchers had been trying
to make sense of what elements might themselves be made of.
The main theory was that every element is made of tiny indivisible chunks of matter called atoms.
Atoms of different elements join together to make up everything you see or touch.
There was just one rather tricky problem with the idea of the atom -
Seeing is believing. Nobody had actually seen an atom.
They're far too small. Lots of physicists were sceptical about their existence.
Ernst Mach, who leant his name to the speed of sound, said,
"They are just things of thought."
The first physical evidence for the existence of atoms would come from a gloriously unexpected source.
From the world of the supernatural.
To the modern mind, William Crookes is a puzzling sort of scientist.
His interests range from discovering new elements to investigating the world of spirits and ghosts.
Crookes' interest in spiritualism was probably triggered by the death
of his younger brother at a tragically young age.
At the same time, there were photographs claiming to show ectoplasm, spirits, apparitions.
Crookes set about a scientific investigation of these claims.
Crookes invited some of the leading mediums of the day to come to his house and be tested
and they passed the test with flying colours.
He claimed to have seen acts of levitation,
an accordion playing by itself
and strange phantom figures, some of which he photographed.
Was Crookes being naive?
Well, it was only decades since the telegraph had been invented.
If you could communicate across the world then why not with the dead?
The thing is, even in his own laboratory, Crookes was coming
across stuff which was very hard to explain, stuff which was really, if you like, out of this world.
This thing here is called a Crookes tube
and it's simply a glass tube out of which the air has been sucked,
a couple of electrodes and a fluorescent screen.
He passed a high voltage across the electrodes...
and the result was really quite striking.
Isn't that gorgeous?
Looks like a sort of green ray.
Was this a spiritual emanation?
Crookes was a careful experimenter.
He found the glow could be bent with a magnet,
suggesting the glow was in some way electrical.
What he did next was very ingenious.
Crookes made a new tube with another addition, a tiny metal paddle wheel.
Let's see what happens when we turn it on.
This suggested the strange glow was made up of moving particles,
something with a mass to push a wheel.
Now Crookes was thrilled.
As far as he was concerned, this proved beyond all reasonable doubt
that what was happening was a stream of particles were making it spin.
He called this force, this stream, "radiant matter",
and he thought it was a sort of fourth state of being.
For all his skills as an experimenter,
Crookes didn't have a convincing theory of what was happening.
But his curiosity would trigger a whole sequence of experiments that would in turn transform physics,
chemistry and also create a whole new way of looking at this deeply strange world that we all live in.
Atomic theory really started to come into focus here in Cambridge University
in the rather unassuming Cavendish Laboratory
with the work of the physicist, Joseph John Thomson, known as JJ.
He realised that what was causing the tube to glow and the paddle wheel to spin, were a stream of
tiny charged particles, particles far, far smaller than even atoms.
He built more accurate and delicate versions of Crookes' tubes.
Thomson calculated the particles causing the wheel to move were 1,000 times smaller than an atom.
It caused a sensation.
They were named electrons, the first sub-atomic particles to be discovered.
It was an achievement that gained JJ Thomson the Nobel Prize for physics in 1906.
A new layer of our understanding of what the world is made of opened up in the early 20th century.
The world was made of atoms
and they were made up of three fundamental particles,
protons and neutrons packed into a nucleus,
surrounded by electrons moving in orbits.
A suitably grand location to give you a sense of the world of the atom is St Paul's in London.
It's a place where you can start to picture the scale and proportions inside the atom.
If you can imagine St Paul's Cathedral as an atom,
then the nucleus, which is at the heart of the atom,
and where almost all the mass resides, would be smaller than a single grain of sand.
The rest is effectively a void.
It is remarkable.
Everything you think of as solid matter, the building, me, you, the floor I'm standing on,
almost all of it is empty space.
That's why, if you took out the empty space, the entire population
of the world could fit inside the size of a single sugar cube.
And scientists soon realised that inside the atom the traditional laws of physics simply don't apply.
In the early days of atomic theory, they thought of the atom as being like a sort of mini solar system.
You've got the nucleus, the sun at the centre and round it spun the electrons like mini planets.
Soon, however, they realised that electrons are nothing like planets.
The electron is an unbelievably weird beast.
And you simply cannot pin it down.
An electron is never just in one place.
It flits around as if it were in many places at the same time.
By the altar, up there in the dome,
just behind me,
all at the same time.
A new theory was required to explain this strange sub-atomic world.
The behaviour of electrons could only be described, not as certainties, but as probabilities.
Not where electrons are, but where they are likely to be.
The new theory was known as quantum.
Niels Bohr, the father of quantum physics,
once said that if you're not profoundly shocked when you hear about it
then you haven't understood it.
Even Albert Einstein initially rejected quantum theory, saying,
"God does not play dice with the universe."
But quantum theory is nonetheless the foundation of our modern technological society.
1945, and the wartime generation celebrated victory and the possibility of peace and plenty.
They dreamt of how technology could make their lives better.
And behind many of these dreams was the science of the electron.
There was a brand-new world and what made it possible were these.
Now it is rather gorgeous, isn't it?
It's a distant cousin of the Crookes tube and its job was essentially
to control the flow of electrons, to amplify or to switch things.
The valve was the workhorse of the electrical industry.
It was used to amplify electrical signals in radios
and telephone exchanges, and to switch binary signals in early computers.
They were manufactured by the million.
The trouble is, big, chunky, uses a lot of power, gets really hot and is incredibly...
The strange world of quantum theory was to provide a replacement.
It was in a telephone company that quantum theory came of age.
Bell Labs wanted a better, cheaper way of connecting Americans.
To do that, they needed to replace the valve.
Their research team was led by William Shockley,
a slick, clever and rather unlikeable individual.
And this is what Shockley's team came up with.
It is a curious looking beast but this is a model of the world's first transistor.
'You can only make a transistor if you understand how electrons behave.
'You need quantum theory.'
But essentially it was doing what a valve does, control the flow of electrons,
but it did so using the laws of quantum mechanics.
Now, I would put the transistor right up there with the ten greatest
inventions of all time, because it utterly transformed the world.
Big, clunky valve radios soon gave way
to small portable transistor radios, and these in turn were replaced by the micro-processer.
It is astonishing when you think that in just 60 years we have gone from this,
a single transistor, to this, a micro-processor that contains over two billion transistors.
For me, the micro-processor is the ultimate expression
of the power that has been unleashed by trying to understand what the world is made of.
Delving ever deeper into matter has undoubtedly changed our society.
The buildings we live in, the way we travel, how we communicate.
In short, our modern way of life is largely a product of the attempts to find out what we're all made of.
Our attempts are far from over.
There will be new layers to discover, ever more strange.
Perhaps what now seems unbelievable is simply what we do not yet understand.
Next time, the most personal question we have asked.
How did we get here?
Michael Mosley takes an informative and ambitious journey exploring how the evolution of scientific understanding is intimately interwoven with society's historical path.
In this episode, Michael demonstrates how our society is built on our search to find the answer to what makes up everything in the material world. This is a story that moves from the secret labs of the alchemists and their search for gold to the creation of the world's first synthetic dye - mauve - and onto the invention of the transistor.
This quest may seem abstract and highly theoretical. Yet it has delivered the greatest impact on humanity. By trying to answer this question, scientists have created theories from elements to atoms, and the strange concepts of quantum physics that underpin our modern, technological world.