James Clerk Maxwell

• 1. Introduction

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  James Clerk Maxwell was three years old, and one phrase was never out of his mouth: "what's the go o' that?" His mother recorded it in 1834, describing a boy fascinated by doors, locks, keys, the hidden course of streams, and how water passed through a wall. He wanted to know how everything worked. That small boy, born in Edinburgh in 1831, would grow into a Scottish physicist whose work Albert Einstein called the most profound and fruitful since the time of Newton. When a Cambridge host once told Einstein he had achieved great things by standing on Newton's shoulders, Einstein corrected him. "No I don't. I stand on the shoulders of Maxwell." How did a country boy nicknamed "Daftie" come to bind together electricity, magnetism, and light? What did he see in Saturn's rings, in a spinning top, in an imaginary demon sorting molecules, that others could not? And why did a man who reshaped physics die at 48, the same age and from the same illness as his mother?

• 2. What's The Go O' That

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  At Glenlair, the country estate in Kirkcudbrightshire that his parents built on 1500 acres, the young Maxwell roamed and questioned. His curiosity outran his schooling. When his mother Frances fell ill with abdominal cancer and died in December 1839, Maxwell was eight years old, and his early education had already been her work. By eight he could recite long passages of John Milton and the whole of the 119th psalm, all 176 verses. He could give chapter and verse for almost any quotation from the Psalms. His first formal tutor was a 16-year-old hired hand who chided the boy for being slow and wayward, and was dismissed in November 1841. Sent at age ten to the Edinburgh Academy, Maxwell arrived in homemade shoes and a tunic, speaking with a Galloway accent that struck the other boys as rustic. They called him "Daftie," and he bore the nickname for years without complaint. He fell in instead with two boys his own age, Lewis Campbell and Peter Guthrie Tait, who became lifelong friends. Maxwell had already rediscovered the regular polyhedra before anyone formally taught him geometry. At 14 he wrote his first scientific paper, on drawing oval curves with a piece of twine, examining ellipses, Cartesian ovals, and curves with more than two foci. Because the boy was deemed too young to stand at the rostrum, James Forbes presented the 1846 work to the Royal Society of Edinburgh on his behalf. The construction was not wholly original, since René Descartes had studied such multifocal ellipses in the 17th century, but Maxwell had simplified them.

• 3. The Color Of Light

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  Forbes's coloured spinning tops gave Maxwell a tool to settle an old puzzle. Mixing red, green, and blue light, he demonstrated that white light could be produced from those three primaries. From 1855 to 1872 he published a series of investigations on colour vision, colour-blindness, and colour theory, work that won him the Royal Society's Rumford Medal. Thomas Young had proposed that the eye perceives colour through three channels, the trichromatic theory, and Maxwell used the recently developed linear algebra to prove it. He invented colour matching experiments and the field of colourimetry to show that three lights could match any colour the eye perceives. That insight pointed straight at photography. If any colour could be reproduced from three lights, then three black-and-white photographs taken through red, green, and blue filters could be projected back through matching filters to rebuild the scene. During an 1861 Royal Institution lecture, Maxwell presented the world's first demonstration of colour photography by this three-colour method. Thomas Sutton, inventor of the single-lens reflex camera, photographed a tartan ribbon three times, through red, green, and blue filters, plus a fourth through yellow that went unused. Sutton's plates were insensitive to red and barely sensitive to green, so the result was far from perfect. A century later, in 1961, researchers concluded the red exposure had partly worked only because ultraviolet light, reflected by some red dyes, slipped past the filter into the wet collodion plate. The same red, green, and blue Maxwell mixed on a spinning top became the basis for colour television.

• 4. Brick-Bats Around Saturn

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  For 200 years no one could explain how Saturn's rings stayed whole, neither breaking apart nor crashing into the planet. St John's College, Cambridge, set the problem as the topic for the 1857 Adams Prize. Maxwell spent two years on it. He proved that a solid ring could not be stable, and that a fluid ring would be torn by wave action into blobs. Since neither matched what astronomers saw, he concluded the rings must be countless small particles, each orbiting independently, which he called "brick-bats." He was the only entrant to make enough headway to submit an essay, and in 1859 he won the £130 Adams Prize for "On the stability of the motion of Saturn's rings." George Biddell Airy, reading it, called it one of the most remarkable applications of mathematics to physics he had ever seen. The verdict held until the Voyager flybys of the 1980s confirmed the rings were indeed made of particles. Those particles, it turns out, are not perfectly stable. Gravity is slowly pulling them down onto Saturn, and the rings are expected to vanish entirely over the next 300 million years.

• 5. The Second Great Unification

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  Around 1862, while lecturing at King's College, London, Maxwell calculated the speed at which an electromagnetic field propagates and found it close to the speed of light. He refused to treat that as coincidence. "We can scarcely avoid the conclusion that light consists in the transverse undulations of the same medium which is the cause of electric and magnetic phenomena," he wrote. His 1865 paper "A Dynamical Theory of the Electromagnetic Field" argued that electric and magnetic fields travel through space as waves moving at the speed of light. The work led him to predict radio waves. His path into the subject began in 1855, when his paper "On Faraday's lines of force" was read to the Cambridge Philosophical Society and reduced existing knowledge to a linked set of differential equations, 20 equations in 20 variables. In "On Physical Lines of Force," published in 1861, he built a conceptual model of induction from tiny spinning cells of magnetic flux, later adding parts on displacement current and on the rotation of polarised light in a magnetic field, the Faraday effect. The famous twenty equations appeared in fully developed form in his 1873 textbook, "A Treatise on Electricity and Magnetism," most of it written at Glenlair. Oliver Heaviside later reduced the theory to four partial differential equations, now collectively called Maxwell's equations. This was the second great unification in physics, the first having been achieved by Isaac Newton. Maxwell believed light needed a medium, the luminiferous aether, permeating all space yet undetectable. The Michelson-Morley experiment could not reconcile it, and those difficulties pushed Albert Einstein toward special relativity, in which he dispensed with the aether as superfluous.

• 6. Demons And Governors

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  An imaginary being capable of sorting particles by energy could, in principle, violate the second law of thermodynamics. Maxwell devised this thought experiment, later named Maxwell's demon, in 1867, and it still frames how information relates to entropy. His work on the kinetic theory of gases ran sporadically through his career. Between 1859 and 1866 he developed a theory of how velocities are distributed among the particles of a gas, later generalised by Ludwig Boltzmann into the Maxwell-Boltzmann distribution, which gives the fraction of molecules moving at a given speed at a given temperature. Peter Guthrie Tait called him the "leading molecular scientist" of his time. After Maxwell died, one observer noted that only one man had ever understood the graphical thermodynamics papers of Josiah Willard Gibbs, "and now he is dead." Maxwell's reach extended into machinery and structure. His 1867 paper "On governors," published in the Proceedings of the Royal Society, mathematically described the centrifugal governors that regulate steam engines, and it became a founding document of control theory and cybernetics. He analysed the rigidity of rod-and-joint frameworks, the trusses used in bridges. He devised modern dimensional analysis, helped establish the CGS system of measurement, and was the first to grasp the concept of chaos, recognising systems with sensitive dependence on initial conditions and emphasising the butterfly effect in the 1870s. In his 1867 paper "On the Dynamical Theory of Gases" he introduced the Maxwell model for viscoelastic materials and the Maxwell-Cattaneo equation for heat transport, threads of work that placed him among the founders of modern electrical engineering.

• 7. Faith, Marriage, And A Quiet Life

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  Maxwell married Katherine Mary Dewar in Aberdeen on the 2nd of June 1858, a year after befriending her father, the Reverend Daniel Dewar, Principal of Marischal College. Katherine was seven years his senior. Comparatively little is known of her, though she helped in his lab and worked on experiments in viscosity, and Lewis Campbell, his biographer, described their married life as one of unexampled devotion. Maxwell's faith ran as deep as his science. At Trinity he joined the Cambridge Apostles, an exclusive debating society where through his essays he tried to work out his Christian understanding. "Let nothing be wilfully left unexamined," he wrote, vowing to ploughed up all fallow land and leave no ground consecrated to Stationary Faith. He underwent an evangelical conversion in April 1853, attended both Church of Scotland and Episcopalian services as a child, and in later years became an Elder of the Church of Scotland. A lover of Scottish poetry, he memorised verse and wrote his own. His best-known poem, "Rigid Body Sings," reworked Robert Burns's "Comin' Through the Rye," and he sang it while accompanying himself on a guitar. Descriptions remark that his intellectual gifts were matched by social awkwardness. For his own conduct he wrote an aphorism, urging that a man keep the work of the day before his eyes, neither despairing over yesterday's work nor turning visionary over tomorrow's, happy if he can see in today's labour a connected portion of the work of life.

• 8. The Last Weeks

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  In April 1879 Maxwell began to have difficulty swallowing, the first symptom of his fatal illness. By then he had returned to Cambridge as the first Cavendish Professor of Physics, appointed in 1871, overseeing every step in the construction of the Cavendish Laboratory and the purchase of its apparatus. Among his last great tasks was editing the research of Henry Cavendish, adding copious original notes, revealing that Cavendish had studied the density of the Earth and the composition of water. Maxwell died in Cambridge of abdominal cancer on the 5th of November 1879, at the age of 48, the same age and the same illness that had taken his mother. The minister who visited him was astonished at his lucidity and the power of his memory in those final weeks. To a Cambridge colleague Maxwell said, "I have never had a violent shove all my life," wishing only, like David, to serve his own generation by the will of God and then fall asleep. He is buried at Parton Kirk, near Castle Douglas in Galloway, close to where he grew up. Lewis Campbell published "The Life of James Clerk Maxwell" in 1882, and Cambridge University Press issued his collected works in two volumes in 1890. In a Physics World survey of the 100 most prominent physicists, Maxwell was voted the third greatest of all time, behind only Newton and Einstein, and near the choir screen at Westminster Abbey a memorial inscription keeps his name.