BBC_James Clerk Maxwell The Man Who Changed the World
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00:00Our planet is filled with signals invisible to the naked eye, but space itself can be
00:28just as noisy. This is Cambridge University's radio telescope observatory. It's used to
00:42examine the far reaches of space, to answer questions about the very origin of our universe.
00:54These magnificent dishes are detecting signals from radiation left over from the Big Bang.
01:00But they're not optical telescopes in the sense of looking through an eyepiece and seeing
01:03a planet or a star. These dishes are detecting radio waves. These telescopes allow us to
01:13see the unseen. Extraordinary images like these are made possible thanks to radio waves,
01:26microwaves and gamma rays. The thing is all these waves are connected. They're all different
01:35types of something we call electromagnetic radiation. Visible light, the light that you
01:41and I can see is just a tiny portion of this broader spectrum of waves. And we use waves
01:47to probe the outer reaches of our universe, but we use them for so much more. In fact,
01:55electromagnetic waves are at the heart of modern technology. We use them every day in
02:00everything from medicine to communications. Our mastery of these waves was made possible
02:10when one man published a set of equations in 1865. A man called James Clerk Maxwell.
02:21His name's barely known to the public, and yet he's probably the finest scientist Scotland's
02:26ever produced. And 150 years after his greatest discovery, I'm setting out to explore the
02:32story of the man and his work. Excuse me, can I ask you a question? Do you recognise
02:46this person? No. Do you know who he is? Alexander Graham Bell? No idea. He looks like a banker
02:54and an economist maybe. James Clerk Maxwell. Still no idea? Still no idea. James Clerk
03:01Maxwell. Never heard of him. Albert Einstein. You're so close! James Clerk Maxwell. Name
03:10ring a bell? Maxwell's Equations. Maxwell's Equations. I don't know what they're about,
03:15but I've heard of them. Right, you do physics? I do physics. Okay, James Clerk Maxwell, and
03:20this is your test. I just failed physics. That's his statue. That's his statue. You
03:28probably pass that quite regularly, do you? Quite regularly, so it's quite an embarrassment
03:31to say I don't know who he is. No, but no one. I've been asking everyone here. James
03:34Clerk Maxwell. No one knows who he is? Any ideas? This is the statue of James Clerk Maxwell,
03:46and yet virtually no one around here knows who he is. But I don't blame them, because
03:51Maxwell seems to have slipped through the cracks of history, at least as far as the
03:55public's concerned. So who was he? James Clerk Maxwell was a 19th century Scottish scientist.
04:06He used his genius to work across a wide range of subjects. Astronomy, physiology, colour,
04:15physics, thermodynamics, electricity and magnetism. He touched on all of these, and
04:23changed many of them beyond recognition. He caused a revolution in physics, and gave us
04:30the laws for one of the four fundamental forces of the universe. Einstein kept a picture of
04:38Maxwell on the wall of his study, and once said, I stand on the shoulders of James Clerk
04:44Maxwell. It's a sentiment shared by many physicists today. Maxwell did for electricity and magnetism
04:51what Isaac Newton did for gravity. He's one of my great heroes. He's one of the greatest
04:56scientists we're ever, ever going to encounter. He's on a par with Einstein, with Newton,
05:01with Archimedes. He transformed our way in which we understand the world. He's probably
05:07the greatest scientist Scotland's ever produced. We're still living in the shadow of his achievements,
05:12and yet no one knows who he is. Even me, a Scot and a scientist, just got this vague notion of what he did.
05:20But I want to change that. I want to rediscover James Clerk Maxwell.
05:32Born in Edinburgh in 1831, Maxwell was the only child in a landowning family from Galloway.
05:42The scientific revolution of the previous centuries was changing our view of the world,
05:48but modern science was still in its infancy.
05:55The 19th century would see groundbreaking discoveries,
06:01and Maxwell would be at the heart of it, compelled by a probing mind.
06:13His inquisitive nature was obvious, even in childhood. When he was a boy, the zoetrope was a new invention, and the young Maxwell loved them.
06:34He was kind of hypnotic. In a sense, these are the forerunners of movies and television.
06:44You can imagine kids in the 19th century just being mesmerised by them. Most of them would have been happy just to sit back and enjoy the show, but Maxwell wanted to know how they worked.
06:55The moving figures are a trick of the eye. Stop the drum spinning, and you can see the simple sketches that help create the moving image.
07:11This simple illusion captivated Maxwell. As a child, he would build his own zoetrope strips to entertain his family and to understand how they worked.
07:22This desire to understand the world around him continued into adulthood.
07:30Ages 14, he produced a paper on geometric shapes that showed such mathematical ingenuity it was published,
07:40and then read at the Royal Society of Edinburgh by an established professor, as James was deemed too young.
07:47As a teenager, he conducted home-made experiments into light and colour.
07:54And by the time he arrived at Cambridge University, aged 19, he'd already published three mathematical papers.
08:05From the age of 14, Maxwell had been using mathematics to explain how the world worked.
08:10It was a talent he would rely on for many of his discoveries, and it was key to establishing his scientific reputation.
08:18Because while still in his twenties, he used maths to solve a riddle that had puzzled scientists for centuries.
08:25Saturn's rings, a vivid band surrounding one of our solar system's giant planets.
08:31We'd become accustomed to their beauty, but in previous centuries, they were an enigma.
08:39Galileo first drew them in 1610, and they immediately fascinated astronomers.
08:44By the mid-19th century, we knew the rings were composed of at least two vast, concentric circles over 250,000 kilometres in diameter.
08:55The rings were so large that they could be seen from a distance of up to a hundred kilometres.
09:02The rings were so large that they could be seen from a distance of up to a hundred kilometres.
09:08The rings were so large that they could be seen from a distance of up to a hundred kilometres.
09:16But what were the rings made of, and why did they stay in place?
09:20In 1855, the Cambridge College published an open competition to answer those very questions,
09:27but the answer would have to be accompanied by a full mathematical proof.
09:32Maxwell's response were enemy stripes as one of Britain's top physicists.
09:39There were three possible explanations for Saturn's rings.
09:43One possibility was that the rings were solid rock or ice.
09:47Another, that they were entirely fluid.
09:51A third explanation said the rings were made up of lots of individual particles that circled Saturn.
09:59As the rings were over a billion kilometres away, proving which explanation was right seemed impossible.
10:05As the rings were over a billion kilometres away, proving which explanation was right seemed impossible.
10:08So how did Maxwell go about disentangling those options?
10:12Well, with great difficulty.
10:14But of course, what's really striking, what's very impressive, is that he did it using pure maths.
10:18And you wouldn't perhaps instantly think that this was a problem you could tackle that way.
10:22You'd think, well, the way to do it is to just build a big telescope and have a look.
10:26But the mathematics that Maxwell brought to bear on this allowed him to look at these three cases
10:32and to basically decide which one of them was the correct answer.
10:36So if we take, first of all, the case of a completely solid ring,
10:40there's a particular mathematical equation that describes that case.
10:44The distance from the centre of the planet to the centre of the rings.
10:48That's this big R here.
10:52The maths is incredibly complicated.
10:56And as a geologist, I'm a bit out of my depth.
11:00But I understand the basic point.
11:04Maxwell reduced the physical world to mathematical symbols
11:08and then used maths to predict what was happening around Saturn.
11:12Maxwell said that a solid ring was possible,
11:16but only if most of the material was bunched together on one side of the planet.
11:20And of course, if you look through a telescope, it doesn't look like that.
11:24So that model was discarded. Back to the drawing board.
11:28Maxwell then assumed that the rings were fluid
11:32and came up with an equation to describe how that might work.
11:36Off he goes with his complicated mathematics.
11:40He found that if the rings were fluid, physical forces acting on them would eventually break them up into lumps.
11:44So he discounted this possibility.
11:48And that leaves the third possibility,
11:52which is that the rings consist of a very large number of independently moving particles.
11:56Particles that are all orbiting Saturn on their own.
12:00And what he boiled all of that down to was an equation to tell you
12:04how many particles you would need in order to have the system stable.
12:08And sure enough, this seemed to work.
12:12So it wasn't just that he'd shown that the other two possibilities were wrong,
12:16but that this third possibility did actually work as well.
12:20What I find staggering is just the notion that you can just use numbers to predict something.
12:24Absolutely. No knowledge about it directly.
12:28I think for me, that's almost a watershed moment in how we do physics
12:32because it laid the foundations for really how we do physics today
12:36because there's many examples, everything from the Higgs boson
12:40to studying distant galaxies where you can make theoretical predictions
12:44and it might be years or decades or even centuries before you can fully test those predictions.
12:48But hey, it works.
12:52We're just zooming in on the ring plane.
12:56That's great, isn't it?
13:00Yeah, amazing.
13:04Here they are. Right on cue.
13:08Would you think Maxwell would have given to have seen this?
13:12Oh, I'm sure he would have loved it.
13:16Almost 130 years after Maxwell's prediction,
13:20there were images that proved his theory beyond doubt.
13:24In 1977,
13:28an ambitious NASA launched the Voyager probe.
13:32Three years later, it sent home sensational images
13:36of Saturn's rings.
13:40In 2009, the Cassini probe confirmed those findings.
13:44Saturn's rings were made of millions of icy rocks.
13:48In recognition of his work,
13:52a division between the rings is known as the Maxwell gap.
13:56But his maths has been applied beyond Saturn.
14:04This image from the Taurus constellation
14:08shows a young sun at the heart of a huge cloud of dust and rocks.
14:12As the cloud circles the star,
14:16we see images where rocks are clumping together to form planets.
14:20We're witnessing the birth of a solar system.
14:24And the maths we use
14:28to understand this process is the same as Maxwell's work
14:32on Saturn's rings.
14:36Maths is a powerful tool that physicists use to understand
14:40and to predict the universe, and Maxwell was a master of it.
14:44To understand the problems of Saturn's rings,
14:48Maxwell had put a marker down.
14:52He wanted the scientific establishment to take him seriously, and they did.
14:56When Maxwell delivered his paper,
15:00it was the only one that the Cambridge Committee received.
15:04No-one else came up with an explanation.
15:08Overnight, Maxwell became known as one of Britain's great theoretical physicists.
15:12It was a shock to those who knew him, because his teenage precociousness
15:16had been followed by groundbreaking experiments as an undergraduate.
15:20So perhaps it's no wonder that Maxwell was made professor
15:24here at Aberdeen's Marshall College at the tender age of 25.
15:28His star was on the rise.
15:32His career may have been taking off,
15:36but this was a difficult time for Maxwell.
15:40Maxwell was extremely close to his parents,
15:44but his mother had died when he was eight,
15:48and just a few months before Maxwell arrived in Aberdeen, he lost his father.
15:52Maxwell expressed his grief in a letter to a friend,
15:56but the passage gives a revealing insight into his humanity
16:00and the deep feelings he had for family and friends.
16:04Either be a machine and see nothing but phenomena,
16:08or see your life interwoven, as it is with many others,
16:12and strengthened by them, whether in life or death.
16:16Maxwell's move to Aberdeen meant he was far from friends,
16:20and amongst colleagues twice his age.
16:24He threw himself into his work.
16:28Whether it was his industry or his solitude,
16:32Maxwell came to the attention of the college principal, Reverend Daniel Dewar.
16:36Dewar befriended his new professor,
16:40and Maxwell became a regular visitor for dinner,
16:44which is how he met the principal's daughter, Catherine.
16:48Maxwell's relationship with Catherine reveals the character of the man beyond his scientific genius.
16:52Deeply affectionate, he had a lively sense of humour
16:56and a passion for poetry.
17:00As their relationship blossomed, Maxwell plucked up the courage to ask Catherine
17:04to share their lives together, and his marriage proposal included a poem.
17:08Will you come along with me on the fresh spring tide
17:12My comforter to be through the world so wide
17:16And the life that we shall lead on the fresh spring tide
17:20Will make you mine indeed, though the world so wide
17:24No stranger's blame or praise will turn us from our ways
17:28That brought us happy days on our own burn side
17:34Maxwell married Catherine in 1858,
17:38and throughout their lives they remained devoted to each other.
17:42She would be a valued assistant
17:46in many of his future experiments, and he even became a willing guinea pig
17:50for one of his great obsessions.
17:54Strange as it may seem,
17:58in Maxwell's time we didn't really know
18:02what colour was, or why we saw colour at all.
18:06In the 17th century,
18:10Isaac Newton had given us food for thought.
18:14By using a prism, he had split sunlight into separate colours,
18:18the familiar colours of the rainbow.
18:22He showed that what we perceive as white light
18:26is actually a mixture of different colours.
18:30Newton said that every colour we see
18:34was the result of mixing the colours we see in the rainbow.
18:38He tried, and failed, to establish the rules of mixing.
18:42150 years later, we weren't much wiser.
18:46Maxwell was interested in colour, and why we perceive it
18:50throughout his life.
18:54And his first real breakthrough
18:58came as a Cambridge student.
19:02Artists seemed to be ahead of scientists on this.
19:06For centuries they had been creating a vast palette of colours,
19:10often by just mixing red, blue and yellow.
19:14Artists referred to these three
19:18as the primary colours,
19:22and using them they could create entirely different colours.
19:26So if a painter was mixing red and yellow, he would get orange.
19:30And if he was mixing blue and red,
19:34then he'd get purple.
19:38But if they were mixing blue and yellow, then they would get green.
19:42As a student, Maxwell read about the work of Thomas Young.
19:46Young thought that there was something significant
19:50about the number of primary colours.
19:54But he also thought biology had a role to play.
19:58Young argued that the human eye had three receptors in it,
20:02each one sensitive to a particular colour.
20:06He argued that the brain worked like a painter, combining messages from each receptor
20:10to develop this perception of colour.
20:14It was a stroke of intuitive genius.
20:18We just didn't have any proof.
20:22Young thought that these receptors
20:26corresponded to the painter's primary colours.
20:30Taken by Young's three-colour theory, Maxwell wanted to test it.
20:34He devised a way to mix
20:38primary colours with mathematical precision.
20:42He then tested those mixtures on a wide range of people
20:46to see if they all perceived the same colour.
20:50And he did this with a deceptively simple tool.
20:54So this looks old. What's this then?
20:58This is Maxwell's original colour wheel, which we are very pleased to have in the laboratory.
21:02So that's the original thing?
21:06Yes, it's been used a lot.
21:10And that's because Maxwell used this to test out the mixing of lights
21:14among all his friends when he was here in Trinity College.
21:18It is pretty antique, as you can see, but the idea is
21:22you put different amounts of the coloured papers here
21:26and then when you rotate them, they mix up.
21:30And this works because the typical time
21:34for a colour to mix is about one minute.
21:38And so if it goes faster, the eye will interpret this as a mixture of the colours.
21:42And this is a motorised version, is it?
21:46This is a motorised version of it, and we can actually demonstrate how the colour mixing works
21:50with this rather pretty demonstration here.
21:54We're going to mix red and blue, we'll rotate it rapidly
21:58and then we'll see which colour we produce.
22:02This is a trick the human eye.
22:06So if you were going to bring up that light... This one here?
22:10Instead of moving figures, he'd be mixing colours just as artists did,
22:14but with mathematical precision.
22:18When he mixed red and blue, he got the same colour artists did
22:22when they mixed paint.
22:26That's kind of magenta. Yes, it's a sort of magenta colour.
22:30If the colour mixing was related to the artist's primary colours,
22:34then perhaps mixing red, yellow and blue in equal measure would produce white.
22:38But it didn't.
22:42So Maxwell tried different combinations.
22:46We can begin now to reveal green as well as blue here.
22:50And if we just do a little bit of fiddling around with these disks,
22:54we'll be able to get equal amounts of red, green and blue
22:58in the colours we observe.
23:18So it's white. It's white.
23:22It's the only colour you'd call that, white.
23:26This is a demonstration of the fact that the primary lights...
23:30Notice the word light, not pigments.
23:34The primary lights are red, blue and green.
23:38And you can create any colour of light by suitable mixture of different proportions of these.
23:42What happens in paintings, pigments absorb light,
23:46whereas this is emitting light.
23:50So the upshot of all of this was that Maxwell was able to produce
23:54a diagram which could indicate how you would create any colour
23:58by mixing the three primary colours.
24:02Maxwell's colour triangle allowed him to pick a specific colour
24:06and work out how much of each primary colour would be needed to reproduce it.
24:10This was made possible by his mathematical precision
24:14and systematic testing.
24:18Maxwell's work swept aside a sea of confusion.
24:22And demonstrated that we see colours in paints differently
24:26to the way we see colours in light.
24:30He established the primary colours for light as red, blue and green.
24:34He realised the receptors in our eyes were sensitive to those three.
24:38And that by mixing them
24:42we perceived a vast range of colours.
24:46A few years later
24:50he provided a stunning display that he was right.
24:58In 1861, Maxwell was invited to the Royal Institution in London
25:02to give a lecture on colour vision.
25:06But he didn't want to just talk about the principles.
25:10He wanted to demonstrate them to his audience.
25:20What he did would astonish them.
25:24Maxwell took three photographs of the same object.
25:28Each photo had a different filter on it.
25:32One was red, one was green and one was blue.
25:36That gave Maxwell three photographic plates that he could use to project an image with.
25:40When Maxwell projected the image from the red photograph onto the wall
25:44he got a red picture.
25:48Although the photography was black and white, this was interesting, but hardly revolutionary.
25:52But if you project all three images onto the wall
25:56at the exact same spot, something special happens.
26:06The audience were looking at the world's first colour photograph.
26:10They were stunned.
26:18Maxwell had chosen the perfect subject for his picture.
26:22A brightly coloured tartan ribbon.
26:26By layering red, green and blue images on top of each other
26:30Maxwell established the possibility of creating colour photographs.
26:34150 years later
26:38we use this method daily because this three-colour principle
26:42is used in colour TV, computer screens, even mobile phones.
26:46The colours we see on our screens, however big or small
26:50are created by carefully mixing the primary colours.
26:58Maxwell's work on colour provides the basis for our present understanding of colour vision.
27:02He even proposed an explanation for why some people were colour blind.
27:06He said the receptors in their eyes were faulty
27:10and that this radically altered how they perceived colour.
27:14Three weeks after his colour show
27:18Maxwell was elected to the Royal Society for his work on Saturn's rings
27:22and on colour. He was now counted amongst the finest physicists in Britain
27:26and he was 29.
27:30Despite his success
27:34a year earlier, Maxwell had found himself out of a job.
27:38When Marshall College merged with Aberdeen University
27:42he had lost out to an older professor.
27:46Out of work, Maxwell and Catherine took a trip to the country
27:50to somewhere very special to James.
27:54A quiet place, hidden deep in Galloway, just west of Dumfries.
27:58A place called Glenlair, his family home.
28:06Maxwell's family had been established in the area for centuries
28:10and he was born in Edinburgh
28:14but James had spent an idyllic childhood here.
28:18Playing in the fields
28:22swimming in the stream, running through the woods
28:26nature truly was his playground
28:30and that fostered the curiosity about how the natural world worked.
28:34For the first decade of his life, Maxwell was homeschooled by his mother.
28:38She encouraged his inquisitiveness
28:42look up through nature, she said, up to nature's God.
28:50Glenlair remained an important place to Maxwell throughout his life
28:54it was somewhere that rooted him, a safe haven
28:58a home.
29:02And the current owner of Glenlair knows just how that feels.
29:06So what was it like growing up at Glenlair?
29:10Well, I was a ten year old little boy when I came here
29:14and I had the run of the place. My dad was quite an old chap
29:18and he and my mother, and I was an only child
29:22they were elderly, so they didn't really keep an eye on me.
29:26My childhood must have almost mirrored his
29:30although I was slightly older.
29:34It's difficult thinking, this seems a good place
29:38for theoretical thinking.
29:42Yes, and we have loads of professors who visit here
29:46and nearly all of them stand here and they look out at that view
29:50and they say, I know how he could do it
29:54because it just inspires you.
29:58Try to encapsulate Maxwell, what is he for you?
30:02What appealed to me about Maxwell
30:06is how normal he was as a boy
30:10that he loved outside, he loved the open air
30:14he loved all the creatures
30:18and the gardens and the trees you see around here, thanks to Maxwell.
30:22But it's that emotional attachment that you feel to him?
30:26Yes, it's the way he loved it here, like I love it here.
30:30I've been offered lots and lots of money to sell this place
30:34but there's no way they're going to get me out except in a box.
30:38Like Duncan, Maxwell felt
30:42a strong connection to Glenlair.
30:46His proposal poem to Catherine had been about sharing their lives here
30:50they'd even honeymooned in Glenlair. When they returned here in 1860
30:54it wasn't just a holiday.
30:58On the death of his father, Maxwell had inherited over a thousand acres of farmland.
31:02Dozens of working people relied on
31:06decisions he made. There were fields to sow
31:10animals to tend, buildings to construct.
31:14He raised funds to build a church and was keen to improve
31:18local schooling. It was a responsibility
31:22he took seriously and every summer Maxwell and Catherine
31:26returned here to oversee the estate
31:30and recapture some of the childhood peace he'd found here.
31:34But Maxwell wouldn't stay at Glenlair.
31:38He wanted to be in the thick of scientific research and that meant
31:42a university. After a rejection from Edinburgh
31:46he accepted a position at King's College London.
31:50Whilst there he would produce his finest work
31:54and unravel one of the great mysteries of his age.
32:06Maxwell arrived in London at the end of 1860
32:10and assumed teaching duties immediately.
32:14While there he focused on a subject that had captured his attention many years before.
32:18Ever since his early days at Cambridge
32:22Maxwell's been interested in electricity after it was suggested as an area to look at
32:26by a friend.
32:30That friend's advice was simple. If Maxwell wanted to learn something about
32:34electricity he needed to know Michael Faraday.
32:38Faraday was a self-taught scientist who was revolutionising
32:42our understanding of electricity and magnetism.
32:46Maxwell's
32:50relationship with him was one of the most fruitful in 19th century
32:54science.
32:58We'd known about electricity and magnetism since ancient times.
33:02Most people had experienced the power of electricity through terrifying
33:06lightning storms.
33:10And we'd used magnetism in ships' compasses for centuries.
33:16They were considered completely separate
33:20things for most of our history.
33:24But in the early 19th century scientists like Faraday were beginning to see a mysterious
33:28connection between the two.
33:32Deep in the heart of the Royal Institution Faraday conducted
33:36experiments to understand how they were linked.
33:40In one
33:44experiment a copper wire carrying electricity somehow provoked
33:48a nearby compass to move.
33:52In another Faraday tried to do the opposite.
33:56Use a magnet to generate electricity.
34:00Which led him to invent the electric generator which this is
34:04an example where you have a permanent magnet and a coil of
34:08wire.
34:12And you push and pull the magnet in and out of the cylinder
34:16to generate an electric current.
34:20That's to show that electricity is passing.
34:24Faraday did not use light emitting diodes.
34:28And all electricity power stations
34:32throughout the world use this principle of generating electricity that
34:36Faraday discovered down here in 1831.
34:40Faraday had generated electricity simply by moving a magnet
34:44through a coiled wire. A discovery that would forever be
34:48associated with his name. But he was left with
34:52perplexing questions. There was no physical contact
34:56between the electric wire and the magnetic needle that moved.
35:00Nor between the moving magnet and the copper coil.
35:04They were affecting each other through seemingly thin air.
35:08But how could that be?
35:12Now what Faraday thought was happening was that there were lines of force
35:16coming out of the end of the magnet
35:20which were then cutting the wire within the coil
35:24to move electricity around the coil.
35:28The idea of mysterious lines coming out of the magnet to generate
35:32electricity may have seemed outlandish. But Faraday had a simple
35:36experiment that could prove their existence.
35:40So I took a very powerful permanent magnet
35:44placed some paper on it
35:48sprinkled iron filings
35:52over it
35:56just to represent the lines of force.
36:00It never fails to impress.
36:04Of the magnet. And you can see the three dimensional structure.
36:08So these are coming up here and swinging around.
36:12And Faraday made permanent
36:16examples of this and sent them around to all his mates in Europe to show that space
36:20has structure as a very strong argument for his field theory.
36:24So Faraday thought there was an invisible force field at work here?
36:28It's literally a field. Faraday still brings the word field
36:32into science. And it's invisible as you say.
36:36So this is why this is just a representation. It shows the existence
36:40of those invisible lines.
36:44Faraday's iron filings experiment
36:48revealed the existence of an invisible field stretching out into thin air.
36:52These fields he thought
36:56were responsible for the experimental results he'd seen.
37:00Despite having physical
37:04proof, Faraday lacked a mathematical description of how the field
37:08was generated or why it affected things around it.
37:12Without a mathematical
37:16proof, many 19th century scientists dismissed the theory
37:20as speculative. But Maxwell had followed Faraday's
37:24work for years and set out to prove him right.
37:32Maxwell had plenty of time to mull over the problem.
37:42The walk from his Kensington home to King's College was an eight-mile round
37:46trip every day. And during the walk, he allowed his mind
37:50to wander. On those walks and at work
37:54he'd company. Apparently Maxwell
37:58always had a dog and he always called it the same name.
38:02From childhood onwards, every dog was called Toby.
38:06And Toby, whichever one it was, rarely left his side.
38:10Toby was a constant companion at home and in the lab.
38:14It's a sign of Maxwell's eccentricity that he would talk to Toby.
38:18He said he liked his company. During his walks
38:22to and from work, Maxwell, perhaps Toby, broodied
38:26over the mysterious relationship between electricity and magnetism.
38:34His aim was to provide a mathematical
38:38explanation for the link between the two.
38:42After years of thinking and who knows how many
38:46miles walking, he came up with a set of equations that described the relationship
38:50between electricity and magnetism.
38:54Equations that would change our lives forever.
38:58Sorry, Frank, but this is just gobbling it to me. I'm just looking at it
39:02trying to make sense of it. Well, it's not much easier for me.
39:06That's what he wrote first of all. And looking at these, they probably mean a little more to me
39:10than to you. But 20 years later, they were written in a simpler form
39:14which is the way that... This form here. That looks more manageable.
39:18But it still looks a bit confused. Could you take us through it then?
39:22Right, well, the first one says that if you've got an electric charge
39:26it spreads an electric field out all over space.
39:30Just like his work on Saturn's rings, each equation is a mathematical
39:34description of something observed in the real world.
39:38So the first equation described how a static electric
39:42charge generates an electric field.
39:46And the second, that
39:50magnetic poles always come in pairs.
39:54The third equation describes how a changing magnetic field
39:58generates an electric field.
40:02And the fourth equation, that an electric current surrounds
40:06itself with a magnetic field. But Maxwell realised
40:10there was something missing. Maxwell's genius
40:14was to realise that each of these equations is fine until you put them together.
40:18And then he realised something was missing, and it was in this final equation.
40:22He said, there has to be another term.
40:30And what this extra piece says is if an electric
40:34field is changing, it will surround itself with a magnetic field.
40:38Which is like the sort of mirror of this equation which says
40:42if a magnetic field is changing, it will surround itself with an electric field.
40:46So just take these two together and just think about it for a second.
40:50If I've got a magnetic field changing, it surrounds itself with an electric.
40:54If the electric is changing, it surrounds itself with a magnetic.
40:58And if that is changing, it will surround itself again with an electric, and so on.
41:02Faraday to Maxwell, electric to magnetic, back and forth, back and forth.
41:06So there's a coupling basically between the two.
41:12Maxwell's equations were saying that electric and magnetic fields
41:16were inextricably linked. Changes in one
41:20created changes in the other.
41:24It helped explain so much.
41:28When Faraday moved these magnet, he changed the position of the magnetic field.
41:32And this triggered an electric field which caused
41:36electricity to flow through the wire.
41:40And when electricity passed through a wire, it wrapped a magnetic field around it,
41:44causing the compass needle to move.
41:48Using pure maths,
41:52Maxwell had unified electricity and magnetism
41:56and shown there were two aspects of the same thing.
42:00One was the electromagnetic field.
42:04This alone would have guaranteed Maxwell's entry
42:08to the Scientist's Hall of Fame.
42:12He could have rested on his laurels.
42:16But whether it was his natural curiosity or the long walks with Toby, he didn't stop there.
42:20He used his equations to test another of Faraday's ideas.
42:24Faraday had guessed that under certain circumstances,
42:28electric and magnetic field lines could be disturbed by waves travelling along them,
42:32almost like ripples on the surface of water.
42:40Maxwell used his equations
42:44to show that the fields could fluctuate in time with each other
42:48and cause what Maxwell called an electromagnetic wave.
42:52He could even measure the speed of the wave.
42:56This says the electromagnetic wave travelled through space
43:00and buried in here, he was able to extract the speed
43:04that the wave travels.
43:08And when he put the numbers in from things that Faraday and others had already measured,
43:12he worked out the speed and it came out as a phenomenal 300,000 kilometres every second, roughly.
43:16And that, I think, is the moment of discovery
43:20because he knew that people had measured the speed of light,
43:24which was 300,000 kilometres every second.
43:28Now, at this moment, you think, is this a coincidence or are these equations telling me something?
43:32And, of course, they're telling you something and the message is
43:36light is an electromagnetic wave.
43:40This was a stunning conclusion.
43:44Maxwell had explained what light itself was.
43:48At the same time, he'd introduced something new to science.
43:52Electromagnetic waves.
43:56And they were destined to change our planet.
44:00The problem was he hadn't physically demonstrated the existence
44:04of these waves. It was all in the maths.
44:08Physical proof would have to come later.
44:12His equations were an astonishing piece of work,
44:16packed with radical ideas.
44:20With his wide theory of electricity and magnetism, he solved the mystery of what light was
44:24and he predicted the existence of these invisible fields
44:28that would directly affect our life.
44:32You know, that's difficult enough to grasp for a 21st century scientist,
44:36but what on earth did the Victorians think?
44:40The fact is, Maxwell was asking a lot from his peers.
44:44Invisible fields, undetected waves, dense maths.
44:48That's difficult enough for 19th century scientists.
44:52Ironically, Maxwell found himself in a similar position to Faraday.
44:56Surrounded by sceptical colleagues and lacking the proof to vindicate his theory.
45:00But a jubilant Maxwell was undeterred.
45:04He wrote an excited letter to his cousin.
45:08I also have a paper afloat with an electromagnetic theory of light,
45:12which until I'm convinced of the contrary, I hold to be great guns.
45:16The guns may have fired,
45:20but it would be a while before they'd be heard.
45:24It took more than 20 years before a German scientist called Heinrich Hertz
45:28found physical proof for electromagnetic waves.
45:32When he was asked what practical use the wave had, he replied,
45:36it's of no use whatsoever.
45:40This is just an experiment that proves Maestro Maxwell was right.
45:44How wrong he was, because Hertz had discovered radio waves.
45:48Marconi invented the radio, and since then
45:52we've been using them to spread radio and television all over the planet.
45:56But this was just the first in a long list of discoveries.
46:04Using higher frequency radio waves, we developed radar,
46:08which now gets used in everything from aviation to geology.
46:12Microwaves were discovered, which we use in cooking and when we use a mobile phone.
46:16Infrared is used in thermal imaging and in most TV remote controls.
46:20Ultraviolet is used in fluorescent lamps,
46:24security marking and medical research.
46:28X-rays have provided us with a valuable medical tool,
46:32but more recently in security.
46:36And gamma rays have been used to detect and treat cancer,
46:40all these things are connected.
46:44Maxwell had shown that light and the colours we see are electromagnetic waves,
46:48but he predicted there would be more.
46:52Today we know that visible light is just a tiny sliver of a
46:56broad spectrum of electromagnetic waves.
47:00And by understanding and exploiting them, we've revolutionised our world.
47:04All thanks to equations Maxwell published
47:08150 years ago.
47:12That was all part of a future
47:16that Maxwell wouldn't see.
47:20When he first published, people didn't understand him.
47:24You know, back in 1865 there was no sign, no evidence of these
47:28mysterious electromagnetic waves.
47:32Maxwell was asking people to believe that these waves could pass through empty space
47:36and things at a distance. It was just too much to ask.
47:40His equations were initially met with a bewildered silence.
47:4419th century scientists were used to thinking of the world in mechanical terms.
47:48Physically tangible objects that could be touched, measured and felt.
47:52Flying in the face of that was
47:56Maxwell's theory, based on dense mathematics and visible fields
48:00and undetected waves.
48:04Maxwell's theory was a kind of abstract mathematical speculation.
48:08That he had strayed too far from physical reality.
48:12That he was, in essence, away with the fairies.
48:16Maxwell became convinced that he had to develop his theory of magnetism
48:20and electricity. Not long after that publication, he decided
48:24to pursue his own interests and resigned his post at King's.
48:28He was going home.
48:34After the
48:38lukewarm reaction to his 1865 publication,
48:42the comfort of Glenlair was welcome.
48:46Ever industrious, Maxwell produced papers on thermodynamics and even topology.
48:50But always he returned to his electromagnetic theory,
48:54slowly refining it.
48:58After six years in the wilderness, Cambridge University approached him.
49:02They wanted someone to plan and run a lab in experimental
49:06physics. Despite all his achievements, Maxwell was
49:10third in line, after two other candidates had rejected the offer.
49:18In 1871, he left Glenlair
49:22for Cambridge, where he designed and built the Cavendish Laboratory,
49:26which would be responsible for discoveries that shaped physics in the 20th century.
49:30And as its first director,
49:34his open-minded approach set the tone for subsequent generations.
49:38I never try to dissuade a man from
49:42trying an experiment. If he does not find out what he wants,
49:46he may find out something else.
49:50The Cavendish Lab would become a phenomenal
49:54success.
49:58It's within these walls that we discovered the electron, and later on,
50:02the neutron. Watson and Crick were
50:06working here when, in 1953, x-rays were used
50:10to show the structure of DNA.
50:14The Cavendish is now widely regarded as a centre of excellence,
50:18and has produced 29 Nobel Prize winners to date.
50:22But every summer,
50:26Maxwell returned to Glenlair, patiently working out the full
50:30implications of his electromagnetic theory of light.
50:42In 1873, Maxwell released
50:46a dynamical theory of electricity and magnetism.
50:50The intervening years had allowed
50:54his colleagues time to digest his theory, and it was starting to gain
50:58traction. But he wouldn't live to see it vindicated.
51:02When guests were visiting Glenlair in 1879,
51:06Maxwell found that he could barely walk down to the river. Such was the pain.
51:10The pain was in his stomach. In October of that
51:14year, he was diagnosed with abdominal cancer,
51:18given a month to live.
51:24Maxwell
51:28was just 48 when he received the news.
51:32He knew his mother had died at the same age,
51:36from the same disease.
51:44Nevertheless, he accepted his fate with a calm stoicism
51:48that had defined his life.
51:52Catherine nursed him as best she could.
51:56It's said that on his deathbed, Maxwell breathed deeply,
52:00and with a long look at his wife, passed away.
52:08James Clark Maxwell
52:12died in November 1879.
52:16He was buried in Parton Kirk, his childhood church
52:20miles from his beloved Glenlair.
52:32He lies in a modest grave next to his parents,
52:36and seven years later, Catherine would be buried next to him.
52:44Apart from a plaque outside the cemetery, there's nothing to
52:48many of the others. There's no list of grand achievements.
52:52It's just simple and modest, like the man himself.
53:00A visitor could be forgiven for passing the grave
53:04without a second glance, but for some, this is a
53:08special place.
53:12There's a story that's told around Parton Kirk.
53:16Shortly after the fall of the Berlin Wall, two buses arrived,
53:20and people filed into the graveyard.
53:24A curious local asked who they were. They were, they said,
53:28Russian scientists who had travelled to visit the grave of
53:32Scotland's Einstein.
53:36You know, Maxwell died at a relatively young age, 48,
53:40which even by the standards of his day was an untimely death.
53:44And you just wonder, you know, given the achievements that he had in his lifetime,
53:48what he would have conjured up if he'd lived if he was 60 or 70.
53:52Maxwell may not have been fully
53:56appreciated in his time, but in the decades following his death,
54:00scientists started to recognise his genius.
54:08Eight years after Maxwell's death,
54:12scientists like Hertz discovered radio waves, proving beyond doubt the existence
54:16of electromagnetic waves.
54:20The rest, as they say,
54:24is history. Over a century later,
54:28these waves have changed our planet and are part of our everyday lives.
54:36But focusing on the technological results of his work
54:40means it's important, because he changed the way we understand
54:44reality itself. Before the work of Maxwell
54:48and of Faraday, just before on the experiments, we understood the world
54:52in terms of springs and cogs, a machine-like world.
54:56And that machine-like world was pretty primitive.
55:00What Maxwell's work showed is that the way that we understand
55:04the interaction between material bodies is via
55:08this idea of a field. Not the sort of field we're standing in...
55:12Not a green field. Not a green field, but something that penetrates space
55:16and which really governs the way the world behaves.
55:24Maxwell helped overthrow the mechanical model of the universe that physicists
55:28had held since Newton, and issued in a new era.
55:32We now think of all the forces in the universe
55:36interacting through fields, rather than direct physical contact.
55:44This was a crucial shift in our understanding, prompting Einstein to say
55:48one scientific epoch ended and another began
55:52with James Clerk Maxwell.
55:56Which is, perhaps, why he's still revered
56:00by scientists today.
56:06This meeting we're having here
56:10in Edinburgh today is very special.
56:14We're celebrating the 150th anniversary of Maxwell's publication
56:18of his equations of electromagnetism.
56:22Some of Britain's finest scientists gather at an event
56:26to remember the life and work of James Clerk Maxwell.
56:30Maxwell is all around us.
56:34The technology that's around us today, computing, fibre optics,
56:38cameras, mobile phones, everything depends
56:42on extensions of those Maxwell's equations.
56:46Without those, we wouldn't be where we are today.
56:50Even the internet doesn't exist without them.
56:54Maxwell changed the way we think forever.
56:58You can't
57:02overestimate his contribution, his influence on everything,
57:06both practical and theoretical.
57:10He is the most remarkable Scot intellectually that has ever arisen.
57:14No question about it.
57:18In terms of the sequence of great men of physics,
57:22starting with Galileo and Newton,
57:26and then Einstein, who said that
57:30Maxwell was the greatest physicist after Newton.
57:34It's wonderful to be sitting in the audience of a meeting
57:38surrounded by Nobel Prize winners, the great and the good.
57:42There's a sense of shared excitement.
57:46It's unapologetic geekiness.
57:50The people like Peter Higgs and Nobel Prize winners,
57:54we are still in awe of this giant of physics.
57:58And having got to know the man,
58:02I can understand why.
58:06You know, I can't blame people for not knowing about James Clerk Maxwell.
58:10This is difficult stuff. I just think that given the breadth of his discoveries
58:14and the sheer impact it's had, that it's a travesty that Maxwell's name's not up there
58:18with Newton and Einstein as one of the greats.
58:22He is Scotland's Einstein. We should remember him as such.
58:34A deadly threat from beneath the waves, next on BBC4
58:38In War at Sea, Scotland's Story.
58:52www.bbc.co.uk