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- Herausgeber: Icon Books
- Kategorie: Wissenschaft und neue Technologien
- Sprache: Englisch
- Veröffentlichungsjahr: 2019
Asked to name a great physicist, most people would mention Newton or Einstein, Feynman or Hawking. But ask a physicist and there's no doubt that James Clerk Maxwell will be near the top of the list. Maxwell, an unassuming Victorian Scotsman, explained how we perceive colour. He uncovered the way gases behave. And, most significantly, he transformed the way physics was undertaken in his explanation of the interaction of electricity and magnetism, revealing the nature of light and laying the groundwork for everything from Einstein's special relativity to modern electronics. Along the way, he set up one of the most enduring challenges in physics, one that has taxed the best minds ever since. 'Maxwell's demon' is a tiny but thoroughly disruptive thought experiment that suggests the second law of thermodynamics, the law that governs the flow of time itself, can be broken. This is the story of a groundbreaking scientist, a great contributor to our understanding of the way the world works, and his duplicitous demon.
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PROFESSOR MAXWELL’S DUPLICITOUS DEMON
THE LIFE AND SCIENCE OF JAMES CLERK MAXWELL
BRIAN CLEGG
Contents
ix
For Gillian, Rebecca and Chelsea
Acknowledgements
As always, thanks to the brilliant team at Icon Books who were involved in producing this book, notably Duncan Heath.
Thanks also to the various experts who have written on James Clerk Maxwell, and to the help from David Forfar and John Arthur of the James Clerk Maxwell Society.
Demonic Interlude I
In which the demon is summoned
I appreciate that demons rarely feature in popular science titles. Not even in books on the god particle,* which is somewhat remiss. Yet a demon I am. I was originally summoned into being by the eminently respectable, God-fearing Scottish professor James Clerk Maxwell, and proclaimed to be a demon by his fellow Scot and physicist William Thomson. I was born – as are so many things in your universe – out of the second law of thermodynamics.
This ‘law of thermodynamics’ business may sound boringly mired in the steam age, and that’s certainly how it originated. But the second law determines how the universe works. Strictly speaking, incidentally, the second law is the third law, as an extra one was added in at the top of the list after the first two were proclaimed, but to avoid – or possibly cause – confusion, the late-comer was named the zeroth law. The second law 2can be phrased in two ways, either of which sounds perfectly innocuous. Yet in those simple statements lie the foundations of reality and the doom of everything.
It’s the second law that decides that effect follows inevitably from cause. It’s the second law that ensures that books on perpetual motion machines remain on the fiction shelves in the library. Indeed, it’s the second law that determines the flow of time in your world (it’s far more flexible in mine). If you could prove that the second law could be broken, you would set chaos loose to reign in the world. As a demon, this sounds an attractive proposition – and it’s appropriate, as breaking that law is exactly what I was created to do.
How does my charge sheet read? You can either say that the law states that heat passes from a hotter to a colder body, or that entropy – the measure of the disorder in a system – always stays the same or increases. But I was brought into being to challenge this law. Do you think it doesn’t matter if some piddling law of physics is broken? This is the law that explains why a dropped glass breaks and never unbreaks. It makes it possible for life to exist on Earth and it predicts the end of the universe. And without it, the many engines that your lives depend on, from cars to computers, would fail. So, don’t disrespect the second law.
The early twentieth-century English physicist and science writer Arthur Eddington† said: ‘If someone points out to you that your pet theory of the universe is in disagreement with Maxwell’s equations [James Clerk M’s masterpiece that describe how electromagnetism works] – then so much the worse for Maxwell’s equations. If it is found to be contradicted 3by observation – well these experimentalists do bungle things sometimes. But if your theory is found to be against the second law of thermodynamics I can give you no hope; there is nothing for it but to collapse in the deepest humiliation.’
Which raises the curtain for me. My sole purpose in life is to show that the second law of thermodynamics can indeed be broken. I enable heat to travel from a colder to a hotter place. Uncomfortably for a demon, I am able to reduce the level of disorder in the world. And if I can truly achieve this, it’s not me, but every physicist since Victorian times who must collapse in the deepest humiliation.
I am, as Churchill might have put it, a riddle, wrapped in a mystery, inside an enigma. Whether anyone has been able to find the key to defeat me remains to be seen in the pages to come. But first, we need to discover the young James Clerk Maxwell.
At the risk of sounding like Frankenstein’s monster, prepare to meet my creator. 4
* For those not familiar with this term, it is a nickname for the Higgs boson, which came to public attention when it was discovered using the Large Hadron Collider at CERN in 2012. Amusingly for those of us with demonic tendencies, physicist Leon Lederman wanted to call his book on the search for the particle The Goddamn Particle, because the Higgs was such a pain to pin down. The publishers objected that this might be considered too irreverent by the public and resorted to the misleading alternative of The God Particle, which really winds up most physicists.
† A man totally lacking in the wondrous beard sported by each of his Scottish counterparts.
Chapter 1
Not a little uncouth in his manners
There was nothing to suggest the coming of a demon in James Clerk Maxwell’s early life. We ought to get that convoluted name untangled first of all. Over the years, those writing about him have never been sure what to call him. Some have resorted to Clerk Maxwell or even an approach he would never have countenanced, the hyphenated Clerk-Maxwell, but his name was not really double-barrelled and ‘Maxwell’ does the job far better.
Maxwell’s father was originally called John Clerk (pronounced to rhyme with ‘park’). This family, existing on the boundary between the upper middle class and the aristocracy, had a complex history. One of Maxwell’s distant ancestors, another John Clerk, had bought the vast lowland Scottish estate of Penicuik, and with it a baronetcy* back in 1646. His second grandson married an Agnes Maxwell, who brought with her the equally impressive estate of Middlebie. Over the years (and quite a lot of intermarrying of cousins) the name ‘Clerk’ was 6always associated with Penicuik and Maxwell with Middlebie – and when appropriately named cousins came together, they sometimes took the name Clerk Maxwell.
By Maxwell’s father’s time, Middlebie was only a shadow of its former self, a ‘small’ 1,500-acre (600-hectare) holding, which is why their estate house ended up a good 30 miles from the town of Middlebie itself. The rest of the estate was sold off to cover some risky speculation in mining and manufacturing by Maxwell’s great-grandfather. John Clerk’s older brother George was the principal heir, but part of John’s inheritance was what was left of the Middlebie estate. This was not an act of generosity on George Clerk’s part. The estate was entailed such that Middlebie and Penicuik could not be held together – otherwise, he would likely have held on to the whole thing. Splitting estates was considered bad form. When John Clerk received this new position, he took the traditional laird’s name, tacking ‘Maxwell’ on after Clerk.
Edinburgh and Glenlair
James Clerk Maxwell was born on 13 June 1831, at his parents’ home, 14 India Street, Edinburgh – now, appropriately enough, the home of the James Clerk Maxwell Foundation. This was a three-storey townhouse on a cobbled street set back from Queen Street, one of the three parallel roads that form the heart of the city. Maxwell was a late and, in all probability, a spoiled child. His mother, Frances Cay before marriage, had lost her first child Elizabeth as a baby. Frances was almost forty when Maxwell turned up.
Maxwell’s father, John, had been a successful advocate (the Scottish equivalent of a barrister), but by the time Maxwell was two, John Clerk Maxwell had settled into his new role 7of country landowner. The family left the Edinburgh house behind, still owning it but renting it out throughout Maxwell’s life. Middlebie had no grand manor, unlike brother George’s imposing Palladian-style Penicuik House,† but John and Frances arranged for a relatively humble home, Glenlair, to be built for them on the farmland known as Nether Corsock.
The social distance between the lively city of Edinburgh and the rural isolation of Middlebie was far more than the 80 or so miles between them suggests. Edinburgh was a modern Victorian city, encouraging scientific and literary thought. Middlebie might as well have remained stuck two centuries in the past. And that 80 miles was made to seem greater still by the difficulties of travelling in rural parts of Scotland. The route, via Beattock, took two complete days, needing a stop along the way. The vehicles available were hardly state-of-the-art. In the biography of Maxwell written just three years after his death by Lewis Campbell, a lifelong friend since school who became a professor of classics, and William Garnett, another friend who was an English electrical engineer, it is noted that:
Carriages in the modern sense were hardly known to the Vale of Urr. A sort of double-gig with a hood was the best apology for a travelling coach, and the most active mode of locomotion was in a kind of rough dog-cart, known in the family speech as a ‘hurly’.
It’s indicative of John’s nature – which seems to have been inherited by his son – that when outbuildings were added to the house 8in 1841, not only did John plan what was required, he drew up the working plans for the builders to use. Although he was a lawyer, according to Maxwell’s early biographers, when not on a case, John ‘dabbled between-whiles in scientific experiment’. He even published a paper in The Edinburgh New Philosophical Journal on an automated printing device entitled ‘Outline of a plan for combining machinery with the mechanical printing-press’. John Clerk Maxwell was exactly the right kind of father to encourage his son to take an interest in the natural world.
Maxwell’s first eight years must have seemed idyllic for a well-off child of the period. His parents allowed him remarkable freedom, neither preventing him from mixing with the local farm children, nor beating out of him the thick Galloway accent he picked up from his friends, which surely must have put a strain on their class-driven sensibilities. In fact, they seem to have been unusually unstuffy for a Victorian family.‡ Theirs was a home where there was little room for formality, but plenty of humour, an approach to life that would later stand Maxwell in good stead.
The estate combined the contrasting terrains of moorland and farmland and ran alongside the curving banks of the River Urr. A small burn feeding the Urr ran at the edge of the meadow beyond the house. By digging out a hollow in the bed of the burn, the Maxwells provided themselves with a swimming pool. Though it would have been freezing cold even at the height of summer, it was no doubt a great attraction for the young Maxwell.
Given their relative wealth, the Maxwells could have readily afforded a tutor for their son. It’s telling that when Mary Godwin 9(later Mary Shelley), the author of Frankenstein, was young, her family was described as being of a ‘very restricted income’, yet her brothers were sent to boarding school and she had ‘tutors in music and drawing as well as a governess’. The Maxwell family was far better off than the Godwins, but displaying an unusual interest in her child for a wealthy parent of the day, Frances looked after Maxwell’s schooling herself. Things would soon change, though. The death of Frances from abdominal cancer in 1839, aged just 47, must have caused the bottom to drop out of the eight-year-old James’s world.
While his father, John, had certainly gone along with Frances’ wish to devote her time to raising the boy, he either wasn’t able or didn’t wish to do the same himself. It was one thing to let the young Maxwell play with his local contemporaries, but the nearby schools were very limited in their educational standards and John could not see his son attending one. For a while, he tried out a young man as a tutor, just sixteen when he took on the job. The teenager had neither the talent nor the experience to keep the bright and curious young Maxwell interested and his efforts failed miserably. Maxwell became difficult and would not accept his lead.
The tutor (whom Maxwell later felt it inappropriate to name) was also rough, even by the standards of the period. Maxwell’s experience apparently included being ‘smitten on the head with a ruler and [having] one’s ears pulled ’til they bled’. As his contemporary biographers who knew him well put it, the effects of this harsh treatment remained ‘in a certain hesitation of manner and obliquity of reply which Maxwell was long in getting over, if, indeed, he ever quite got over them’.
In this difficult time, Maxwell’s release was the chance to roam free on the estate, observing the natural world close-up. 10This is something that his father had always encouraged, and Maxwell took a particular interest in the variations in colour he saw in nature. He was especially interested in crystals, which fascinated him in the way that their colours changed as they were put under pressure. His father’s friend, Hugh Blackburn, a professor from Glasgow University, added a novel delight, allowing Maxwell to help him launch a series of hot air balloons from the Glenlair estate.
Maxwell had the usual youngster’s excitement and interest in everything around him. According to the early biography, among his favourite phrases were ‘Show me how it doos’, and ‘What’s the go o’ that§?’ This enthusiastic curiosity about the world around us seems natural in youth – speak to children at primary school and you can’t miss the way that they are enthused by science – but many lose that sense of wonder during their secondary school years. Maxwell held on to a childlike fascination for the rest of his life.
The Academy
It was clear, though, that the attempt to use the failing tutor to deal with Maxwell’s education was a disaster that could not be sustained; Frances’ sister, Jane Cay, who lived in Edinburgh, came to the rescue. She suggested to John that Maxwell could come to live in the city with John’s unmarried sister Isabella. Isabella’s house was ideally placed to walk to the prestigious Edinburgh Academy – Maxwell could get a decent education and live under the supervision of his aunts during term time, then return to roam free on the Glenlair estate in the holidays. This wasn’t, however, a matter of his father dismissing Maxwell 11solely to his aunts’ care – in the winter particularly, John Clerk Maxwell spent regular evenings in Edinburgh with his son.
Glenlair wasn’t a grand aristocratic country house – it was effectively a large farmhouse,¶ though Maxwell would extend it considerably in the 1860s. It was big enough to entertain and to have space for Maxwell’s scientific ventures when he was older, but on a scale where it still felt homely. Glenlair would remain an important focal point for Maxwell throughout his life.||
Despite the suggestion that he was rendered hesitant by the bad treatment of his tutor, Maxwell seems not to have been a sensitive child. And it’s just as well, given his reception when he was sent to the Edinburgh Academy for the first time at the age of ten. Schoolchildren have never been slow to pick on those who are different, and Maxwell offered them rich opportunities for mockery, especially as the first-year class was full and so he was plunged straight in with older, better-established boys.
It wasn’t just his accent, marking him out as provincial, that made the young Maxwell a target for mockery. He arrived at the school dressed in a combination of tweed jacket, frilly-collared shirt and brass-buckled shoes that were guaranteed to make him look like a mongrel throwback from fashion history. Maxwell reported that he returned home on the first day with his tunic 12reduced to rags, though he appeared to find this more amusing than frightening.
The Academy was a relatively new school, which had been open for just eighteen years when Maxwell first attended. It was set up to compete with the classical education provided by English public schools. As such, it had a focus on giving its pupils independence and hard discipline alongside a rigid curriculum that focused intensely on the classics with perhaps a spot of maths; there was very little science. As the father of the founder of the Scouting movement Robert Baden-Powell commented in 1832: ‘Scientific knowledge is rapidly spreading among all classes except the higher, and the consequence must be, that that class will not long remain the higher.’
Having such a limited curriculum seemed to be a mark of pride in the public schools. John Sleath, High Master of the prestigious St Paul’s School in London during the early part of the nineteenth century, wrote to his parents: ‘At St Paul’s School we teach nothing but the classics, nothing but Latin and Greek. If you want your boy to learn anything else you must have him taught at home, and for that purpose we give him three half-holidays a week.’
This was a period when public schools were hardly centres of excellence. For example, the pupils of Rugby School took their masters prisoner at sword-point and were overcome after the reading of the Riot Act resulted in an armed rescue. With very little parental supervision, many schools, even the big names, provided a shoddy education in return for their fees. At Eton, to keep the costs of teaching staff down, boys could be taught in groups that were nearly 200 strong. While conditions were not so extreme at Edinburgh, in Maxwell’s early years, classes could have 60 or more pupils. 13
However, reforms were underway in the school system, with more opportunity to have a ‘modern’ side as an alternative to the classics, and Edinburgh Academy was arguably more up-to-date in its approach than many of its older English equivalents. Even so, not used to the pressures of school life, having always had the time to think at his own pace, Maxwell came across as slow to learn. A combination of this and his rural accent earned him the nickname Dafty, which stuck even when it became clear that he was extremely academically gifted. Inevitably, though, so far away from his familiar home and the estate, it took Maxwell a while to bed in. A classmate called him ‘A locomotive under full steam, but with the wheels not gripping the track’.**
Maxwell was not exactly a loner at school, but simply seemed to carry on as he had before, doing his own thing – if others wanted to join him, that was fine, but he seemed in no hurry to conform. Thankfully, his aunts quickly provided him with more conventional clothing when it was realised that his dress appeared more than a little eccentric. Maxwell certainly seemed comfortable when at home at Isabella’s house, 31 Heriot Row, a handsome four-storey grey stone townhouse with a small park out the front. He had a chance to explore both the house’s excellent library and what the natural world of Edinburgh had on offer for him to observe. Though the school took boarders, it always had day boys as well, including Maxwell.
With time, Maxwell’s limited social contact at school grew. A like-minded student who did not consider it embarrassing to 14be academic, Lewis Campbell moved to live near Heriot Row, and soon the two boys spent their journeys to and from school together, developing a strong bond that would last a lifetime. They had now reached an age when the school added mathematics to its limited classical curriculum – something omitted in the first two years – and Maxwell not only found that he excelled at the subject, but that he and Campbell shared a love of maths (and a certain amount of rivalry in their ability to solve mathematical problems).
Once this barrier was broken through, it seemed easier to gain friends who had an interest in science and nature, notably Peter Tait. Another lifelong friend, Tait would himself go on to become one of Scotland’s leading physics professors, in his early career even managing to beat Maxwell to take an academic post. At school, Maxwell came second to Tait in mathematics in 1846 (at the time his best subjects were scripture, biography and English verses) but pulled ahead in 1847. When secure in his little group with Tait and Campbell, Maxwell loved the opportunity to puzzle through mathematical and physical challenges, something that inspired him at the age of fourteen to come up with his first academic paper – though strangely his investigations owed as much to the arts as the sciences.
The young mathematician
Maxwell’s father regularly took him to meetings of both the Royal Society of Edinburgh and the Royal Scottish Society of Arts (RSSA). It was here that Maxwell became familiar with the work of the local artist David Ramsay Hay. In Hay’s philosophy, Maxwell found a point of view that was similar to his own – Hay both delighted in the beauty of nature and wanted to apply scientific measurements to it. Maxwell would later spend much effort 15on the nature of colour and colour vision – Hay was interested in a mathematical representation of the beauty of colour. But, equally, Hay was fascinated by the mathematics of shape and it was here that Maxwell’s paper seems to have drawn its inspiration. Hay would later give a paper at the RSSA on ‘Description of a machine for drawing a perfect egg-oval’. Maxwell’s youthful paper was on the subject of curves such as ovals that can be drawn using a pencil, a piece of string and pins.
Maxwell’s experimental apparatus resembled a primitive version of the popular 1960s toy Spirograph. By placing pins through a sheet of paper into a piece of card and looping a length of string around the pins, it’s possible with some care to draw simple geometric shapes. With a single pin, you get a circle. Two pins produce the dual foci of an egg-like ellipse. This much was standard school fare, but Maxwell took the investigation significantly further. He looked at what would happen with the string tied to one or more pins and the pencil, allowing for different numbers of loops around each of the two pins, and worked out an equation that linked the number of loops, the distance between the pins and the length of the string.
Maxwell shared his work with his father, who showed it to his friend James Forbes, Professor of Natural Philosophy†† at Edinburgh University. Fascinated by this precocious piece of work, Forbes brought in a mathematician from the university, 16Philip Kelland, who checked through the literature for precedents.‡‡ Although some similar work had been done by the French scientist and philosopher René Descartes, Kelland discovered that not only was Maxwell’s approach simpler and easier to understand than Descartes’, it was more general than the results that Descartes had published.
Given the originality of young Maxwell’s work, Forbes was not going to let the effort go by rewarded with nothing more than a pat on the head. He managed to present Maxwell’s paper, now grandly titled ‘Observations on Circumscribed Figures Having a Plurality of Foci, and Radii of Various Proportions’, at the Royal Society of Edinburgh in April 1846. The fourteen-year-old Maxwell could not present the paper himself as he was both too young to do so and not a member, but he had regularly attended Royal Society meetings with his father and was present to hear his work read. The paper was well received and cemented Maxwell’s growing feeling that his future lay in science and mathematics. It is too long (and, frankly, too boring) to reproduce here, but here is the opening sentence to get a feel for the young Maxwell’s precocious (and somewhat long-winded) output:
Some time ago while considering the analogy of the Circle and the Ellipsis – and the common method of drawing the latter figure by means of a cord of any given length – fixed by the ends of the foci – which rests on the principle, that the sum of the two lines drawn from the foci to any point in the circumference is 17a constant quantity, it occurred to me that the Sum of the Radii being constant was the essential condition in all circumscribed figures, and that the foci may be of any number and the radii of various proportions.
Maxwell must have been delighted to see as august a body as the Royal Society of Edinburgh begin the description of his work with: ‘Mr Clerk Maxwell ingeniously suggests the extension of the common theory of the foci of the conic sections to curves of a higher degree of complication in the following manner:—.’ Although Maxwell continued with his general education, he began to read voraciously from the books and papers of the scientific greats, developing a particular affection for the down-to-earth approach of the self-taught English scientist Michael Faraday, who had become a leading light of the Royal Institution in London by the time Maxwell was at school.
Churchman and country squire
We tend these days to make a clear distinction between scientific study and religious beliefs, but Maxwell came from the last generation in the British tradition where there was no feeling of conflict between the two. Like many of the scientific greats before him (including Faraday and, in his own strange way, Newton), Maxwell had a deeply held religious faith. On his breaks from Edinburgh, back home in Glenlair, the family and their servants would join together each day in prayer, and the entire household made the five-mile trek each Sunday to attend the Presbyterian Church of Scotland’s Parton Kirk – where his mother was buried, in a grave inside the ruins of the Old Kirk that would eventually also hold his father, Maxwell himself and Maxwell’s widow. While he was in Edinburgh, his Aunt Jane 18made sure this observance was kept up, taking him to attend both Episcopal and Presbyterian churches, cementing a religious faith that remained strong throughout Maxwell’s life.
Regular breaks at Glenlair would remain an essential for Maxwell, whether he was a student or professor. It was a total break from the bustle of the city or the rigours of an academic institution. In his obituary for Maxwell, his friend Peter Tait would comment of his schooldays:
[H]e spent his occasional holidays in reading old ballads, drawing curious diagrams, and making rude§§ mechanical models. His absorption in such pursuits, totally unintelligible to his schoolfellows (who were then quite innocent of mathematics), of course procured him a not very complimentary nickname …
Wherever he worked as an adult – he would later be based in Aberdeen, London and Cambridge – Maxwell’s summers would be spent on the Glenlair estate. When at home, in almost all respects, Maxwell would be a typical country gentleman of the period – except for his unusual enthusiasm for and delight in nature. Where most of his contemporaries enjoyed nothing better than a mass slaughter in the shooting season, Maxwell never took part in hunting and shooting.
Even though he continued to live at 31 Heriot Row with Aunt Isabella, the influence of Maxwell’s family was about to wane, as he transferred from the Academy to Edinburgh University at 19the age of sixteen. It might seem after his clear demonstration of mathematical originality that he would have already set his sights on a mathematical or scientific career, but this was a period when professional scientists like Michael Faraday and Faraday’s former boss Sir Humphry Davy were in the minority. The word ‘scientist’ was only coined in 1834 when Maxwell was three, and took a while to settle in. Some alternatives of the period were ‘scientician’ and ‘scientman’. Maxwell is often considered one of the first truly modern scientists.
It was not that landed gentry did not partake in science. It was just that someone of Maxwell’s status was far more likely to perform their scientific work as an amusement, a hobby to pass the time – so Maxwell’s original intention had been to follow his father in entering the law. However, Edinburgh University was still using the traditional broad approach of the ancient university curricula, so had both mathematical and natural philosophy (science) content in its degree course. It’s notable from a letter that Maxwell wrote to Lewis Campbell in November 1847 that the maths and science were the parts that dominated his interest:
As you say, sir, I have no idle time. I look over notes and such like until 9.35, then I go to Coll., and I always go one way and cross streets at the same places; then at 10 comes Kelland [mathematics lecturer, Philip Kelland]. He is telling us about arithmetic, and how the common rules are the best. At 11 there is Forbes [Maxwell’s father’s friend, the physics professor], who has now finished introduction and properties of bodies, and is beginning Mechanics in earnest. Then at 12, if it is fine, I perambulate the Meadows; if not, I go to the Library and do references. At 1 I go to Logic [with Sir William Hamilton].
20The only passing mention of the classics in his letter is to say, ‘I intend to read a few Greek and Latin [textbooks] beside’. Classics was a compulsory part of the majority of university courses. There is no mention at all of the law – this would be picked up after his university degree.
Perhaps most importantly, Maxwell had access to the university’s limited laboratory equipment (likely to be in an outhouse, as there was no purpose-built lab at Edinburgh in 1847) when he had the time, encouraged by family friend Professor James Forbes. It was here, and in a workroom at Glenlair during the long summer vacation, as much as in the formal training he received at the university in logic and natural philosophy, that Maxwell’s unstructured, youthful scientific curiosity was forged into a first-class scientific mind.
The university life
At the time, some of the personal oddities that had got Maxwell mocked at school still remained part of his nature. His early biographers note: ‘When he entered the University of Edinburgh, James Clerk Maxwell still occasioned some concern to the more conventional among his friends by the originality and simplicity of his ways. His replies in ordinary conversation were indirect and enigmatical, often uttered with hesitation and in a monotonous key.’ While he grew out of this (apart, apparently, from when ‘ironically assumed’), his relative frugality, preferring the third-class railway carriage to the first, and a tendency to lose himself in thought while at the dinner table would remain with him for life.
The experimental side of the course at Edinburgh was limited and sometimes verged on the amateurish. Maxwell noted in a letter to his friend Lewis Campbell: 21
On Saturday, the natural philosophers ran up Arthur’s Seat with the barometer. The Professor [presumably Forbes] set it up at the top and let us pant at it till it ran down with drops. He did not set it straight, and made the hill grow fifty feet; but we got it down again.
The barometer in question was likely to be an inverted tube of mercury, measuring atmospheric pressure which was then used to calculate the height above sea level of the famous rocky outcrop above Edinburgh.
In the same letter, Maxwell makes a first mention of a devil that would be a companion for much of his life – though not the titular demon of this book. He wrote:
Then a game of the Devil, of whom there is a duality and a quaternity of sticks, so that I can play either conjunctly or severally. I can jump over him and bring him round without leaving go of the sticks, I can also keep him up behind me.
This refers to the game known as ‘the devil on two sticks’, now more commonly called diabolo, where a double cone, joined point to point, is kept in the air using a string between two rods.
For much of his career, Maxwell would supplement his academic work with experiments in a series of home laboratories that would eventually have been better equipped than a university. It was not until he was involved in setting up the prestigious Cavendish Laboratory in Cambridge (see Chapter 8) that he would have significant access to a professional, university-based workshop. During his time at Edinburgh University, he got together a small lab at Glenlair in a room over the wash-house. In the summer of 1848 (when Maxwell was seventeen), he wrote to Lewis Campbell: 22
I have regularly set up shop now above the wash-house at the gate, in a garret. I have an old door set on two barrels, and two chairs, one of which is safe, and a skylight above, which will slide up and down.
On the door (or table), there is [sic] a lot of bowls, jugs, plates, jam pigs,¶¶ etc., containing water, salt, soda, sulphuric acid, blue vitriol,|||| plumbago ore;*** also broken glass, iron and copper wire, copper and zinc plate, bees’ wax, sealing wax, clay, rosin, charcoal, a lens, a Smee’s Galvanic apparatus,††† and a countless variety of little beetles, spiders, and wood lice, which fall into the different liquids and poison themselves … I am making copper seals with the device of a beetle. First, I thought a beetle was a good conductor, so I embedded one in wax (not at all cruel, because I slew him in boiling water in which he never kicked), leaving his back out, but he would not do.
Although Maxwell was busy with his experiments that summer, it didn’t stop him from writing highly mathematical papers. He had continued to do this since his first success at the Royal Society of Edinburgh aged fourteen, though often the documents were 23just handwritten for the consumption of his friends. However, in 1848 he wrote a paper stretching to 22 long pages called ‘On the Theory of Rolling Curves’, published the following year in the Transactions of the Royal Society of Edinburgh. This combines geometry with some sophisticated algebra and calculus, describing how one curve, rolling along another curve (which is ‘fixed to the paper’) would produce a third curve.
Quoted in the biography by Campbell and Garnett, Maxwell remarks that his decision to switch from a legal track was made to pursue ‘another kind of laws’. Most undergraduates content themselves with the work programme that the university sets, but Maxwell was already at his best when exploring on his own, continuing his early experiments with some remarkably sophisticated developments – something that comes across particularly in his work on stress and polarised light.
A particular light
Maxwell had been introduced to the topic of polarisation – a variation in the direction of oscillation of waves of light, which can be separated by special materials – while still at school. His mother’s older brother, John Cay, took Maxwell and Lewis Campbell to visit the optical expert William Nicol, who had found a way to produce polarised light at will.
The concept of polarisation dated back to 1669, when Danish natural philosopher Erasmus Bartholin had been the first to explain the workings of an odd crystal known as Iceland spar. This is a form of calcite – crystalline calcium carbonate. If you put a chunk of the transparent crystal on top of, say, a document, you see not one, but two copies of the writing, shifted with respect to each other. The phenomenon itself had been known for centuries – it has even been suggested that the Vikings may 24have used ‘sunstones’ with a piece of Iceland spar in them as a navigating device to estimate distances. But Bartholin’s insight was to realise that the crystal split two different forms of light that were both present in ordinary sunlight.
When at the start of the nineteenth century Thomas Young demonstrated that light was a wave that rippled from side to side as it moved forward (known as a lateral or transverse wave), the French physicist Augustin Fresnel realised that this provided an explanation for the special ability of Iceland spar. Light waves from a source such as the Sun would be oriented in all directions – some would be rippling side to side while others oscillated up and down – in fact the waving could take place in any direction at right angles to the direction of the light beam’s travel. If the crystal split apart waves rippling in different directions – the direction of the side-to-side ripple being described as its direction of polarisation – then the two images could be the result of the crystal separating rays with two different directions of polarisation.
When Maxwell’s uncle John Cay took him and his friend to visit William Nicol, they were shown prisms made from Iceland spar which had the effect of splitting off just one polarisation of light (for a time these optical devices were known as nicols, after their maker). This seems to have inspired Maxwell while he was at Edinburgh University, with polarised light soon becoming the prime focus of his spare-time experiments. It was known that when such light is passed through ordinary glass there is relatively little effect. However, if the same light is shone through unannealed glass, glass that has been heated until it is glowing and then cooled very quickly, the polarised light produces a coloured pattern, caused by the internal stresses in the glass. 25
Initially, Maxwell experimented with pieces of window glass, heating them to red heat then rapidly cooling them.‡‡‡ In a letter to Lewis Campbell he wrote:
I cut out triangles, squares, etc., with a diamond, about 8 or 9 of a kind, and take them to the kitchen, and put them on a piece of iron in the fire one by one. When the bit is red hot, I drop it into a plate of iron sparks [filings] to cool, and so on till all are done.
To produce polarised light, he made his own polarisers using a matchbox with pieces of glass set in it to produce reflections (reflected light is partially polarised); he also attempted to make polarisers from crystalline saltpetre (potassium nitrate). Maxwell made watercolour paintings of the brightly coloured patterns that he obtained in his heated and cooled window glass, some of which he sent to William Nicol, who was sufficiently impressed to send Maxwell a pair of his optically precise nicols, producing far better polarised light than Maxwell had been able to obtain with his do-it-yourself matchbox devices.
From an engineering viewpoint, getting an understanding of the stresses inside an object is essential to predict how it will stand up to strain when it is put in use. Maxwell had the insight to see that if, for example, a girder could be made of a transparent material, it would be possible to use polarised light to study the internal stresses as the girder begins to bear a load. Clearly this isn’t possible using an actual iron or steel girder – but if a model of it could be constructed in a suitable transparent 26material, it could be used to discover how stresses form in the structure and change under load, reducing the risk of structural collapse.
Unfortunately, glass doesn’t respond well to strain, and the clear plastics and resins that would later be used in this ‘photoelastic’ method that Maxwell devised, and which is still used by engineers, weren’t available at the time. Instead, with that same make-do-and-mend approach that had seen him attempt to use beetles as part of his electrical toolkit, he got hold of some gelatine from the Glenlair kitchen and used it to make clear jelly shapes. Maxwell was delighted to discover that his jellified models produced exactly the kinds of stress patterns he hoped for as he put them under strain.
The path to Cambridge
When not doing experiments, Maxwell would be working through numerous physical propositions or ‘props’ as he and his friends called them, often studying the most mundane of objects and trying to deduce something interesting from them. Sometimes these can seem a little bizarre. For example, in a letter written from Glenlair in October 1849 he noted: ‘I have got an observation of the latitude just now with a saucer of treacle, but it is very windy.’
As well as more practical work, Maxwell followed up his pin and string mathematical paper and other topics while still an undergraduate. His most outstanding attempt of the period was to derive a mathematical analysis of the stress patterns he had observed using his photoelastic technique. He confirmed these mathematical formulae, covering different basic 3D shapes such as cylinders and beams, as much as he was able with his experimental work. This was a remarkable achievement for someone 27with his very limited experience, but he was to discover that it wasn’t enough to perform careful experiments or to produce mathematics that successfully described them. It was also important that you could communicate your scientific findings effectively. He wrote up his work and asked Professor Forbes to present it to the Royal Society of Edinburgh.
Forbes may have been highly impressed with the younger Maxwell’s ventures into mathematics, but this new paper was more directly impinging on his own field, and Maxwell was now nearing adulthood. Forbes did not think much of his writing style in the paper, which was refereed by Maxwell’s mathematics lecturer, Philip Kelland. Forbes commented that Professor Kelland ‘complains of the great obscurity of several parts owing to the abrupt transitions and want of distinction between what is assumed and what is proved in various passages’.
Professor Forbes went on to say: ‘it must be useless to publish a paper for the use of scientific readers generally, the steps of which cannot, in many places, be followed by so expert an algebraist as Prof. Kelland; – if, indeed, they be steps at all …’ This kind of criticism could have been deadly for a beginner who took it personally, but it spurred Maxwell into studying the best of the period’s scientific writing, analysing the wording and structure to see what made it effective and incorporating what he discovered into his own style. While he never became one of the greats of science communication, after this his papers were usually lucid and well written.
There was something about Maxwell’s personality that made him able to adapt well to constructive criticism in this way. He seems to have had the ideal balance of freedom to experiment and try things out, with a network of peers who were prepared to point out his failings and help him overcome them. Like 28his scientific hero Michael Faraday, Maxwell never gave himself the airs and graces of some of their contemporaries such as Sir Humphry Davy in London or, in later years, Maxwell’s regular correspondent William Thomson, who would become Sir William and then Lord Kelvin. Maxwell’s religious upbringing, his mixing with the country children on the estate and his down-to-earth humour seem to have protected him from ever having an over-inflated sense of his own importance.
Maxwell’s paper on the mathematics of the stresses observed in his photoelastic experiments was originally submitted to Professor Forbes in December 1849. After Forbes and Kelland’s feedback, Maxwell redrafted it in the spring of 1850 and the revised version, which had large chunks of the original omitted or reworded, appeared in the Transactions of the Royal Society of Edinburgh that year. It was a long piece of work running to 43 pages, which combined some of his own experimental observations with a much wider mathematical analysis.
Although Edinburgh allowed Maxwell considerable freedom in pushing forward his scientific thinking, it was still primarily seen as a track for him to achieve a degree on the way to a career in law. But as he wrote to Lewis Campbell on 22 March 1850:
I have notions of reading the whole of Corpus Juris and Pandects [for his studies of law] in no time at all; but these are getting somewhat dim, as the Cambridge scheme has been howked up from its repose in the regions of abortions, and is as far forward as an inspection of the Cambridge Calendar and a communication with Cantabs.§§§
29Maxwell decided that after three years at Edinburgh University, before he had completed his degree, he needed a more thorough scientific and mathematical content to his studies and applied to Peterhouse college, Cambridge, where his friend Peter Tait was already resident. Such a move was not uncommon. Tait had left Edinburgh for Cambridge after just one year and another friend, Allan Stewart, after two years. This change of academic venue required Maxwell’s father’s support, which seems to have been given wholeheartedly. John Clerk Maxwell travelled down to Cambridge with his son on 18 October 1850, as the young scientist started on the next leg of his academic journey. 30
Notes
1 – The description of travel to the Maxwell estate is from Lewis Campbell and William Garnett, The Life of James Clerk Maxwell (London: Macmillan, 1882), p. 26.
2 – The idea that Maxwell’s father undertook scientific experiments is from Lewis Campbell and William Garnett, The Life of James Clerk Maxwell (London: Macmillan, 1882), p. 4.
3 – John Clerk Maxwell’s paper ‘Outline of a plan for combining machinery with the manual printing-press’ was published in The Edinburgh New Philosophical Journal, 10 (1831): 352–7.
4 – The assertion that the family of Mary Godwin (Shelley) was of ‘a very restricted income’ despite having a governess is from Kathryn Harkup, Making the Monster (London: Bloomsbury Sigma, 2018), p. 11.
5 – The ill treatment of Maxwell by his tutor is recorded in Lewis Campbell and William Garnett, The Life of James Clerk Maxwell (London: Macmillan, 1882), p. 43.
6 – Maxwell’s early questions about how things worked are recorded in Lewis Campbell and William Garnett, The Life of James Clerk Maxwell (London: Macmillan, 1882), p. 12.
7 – Maxwell’s arriving back with his tunic in rags after his first day is described in Lewis Campbell and William Garnett, The Life of James Clerk Maxwell (London: Macmillan, 1882), p. 50.
8 – Descriptions of contemporary English public schools and their limited curricula are from David Turner, BBC History, ‘Georgian and Victorian public schools: Schools of hard knocks’, June 2015, available at https://www.historyextra.com/period/georgian/georgian-and-victorian-public-schools-schools-of-hard-knocks/
9 – Baden Powell’s concern that the higher classes were not gaining scientific knowledge is quoted in Pietro Corsi, Science and Religion: Baden Powell and the Anglican Debate, 1800–1860 (Cambridge: Cambridge University Press, 1988), p. 116.
10 – Maxwell’s first paper at the age of fourteen is in Proceedings of the Royal Society of Edinburgh, Vol. 2 (April 1846) and reproduced in Peter Harman (ed.), The Scientific Letters and Papers of James Clerk Maxwell, Vol. 1 (Cambridge: Cambridge University Press, 1990) pp. 35–42.
11 – The description of Maxwell’s holiday activities at Glenlair is from 270Peter Tait, ‘James Clerk Maxwell: Obituary’, Proceedings of the Royal Society of Edinburgh, Vol. 10 (1878–80): 331–9.
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