{"id":6748,"date":"2016-06-13T08:58:13","date_gmt":"2016-06-13T07:58:13","guid":{"rendered":"https:\/\/blogs.ua.es\/fisicateleco\/?p=6748"},"modified":"2018-04-14T14:19:34","modified_gmt":"2018-04-14T13:19:34","slug":"james-clerk-maxwell-june-13-1831","status":"publish","type":"post","link":"https:\/\/blogs.ua.es\/fisicateleco\/2016\/06\/13\/james-clerk-maxwell-june-13-1831\/","title":{"rendered":"James Clerk Maxwell, \u00abthe man who changed the world forever\u00bb, was born on this day in 1831"},"content":{"rendered":"

James Clerk Maxwell<\/strong><\/p>\n

Maxwell is considered as one of the most important scientists of all time and one of the greats in the history of physics, along with Newton and Einstein. Undoubtedly, his more important scientific contribution is the theory of the electromagnetic field, fundamental not only for the comprehension of natural phenomena, but also for its technical application, in particular in the today ever-present field of telecommunications. He was born in Edinburgh, Scotland, on 13 June 1831 to a well-established family. Two years later, the family moved to a small country estate in Middlebie, Galloway, about 90 miles southwest of Edinburg. His father had been inherited his estate and there he enthusiastically began to supervise the construction of a new house, which he called \u201cGlenlair.\u201d In Glenlair James Clerk Maxwell not only spent long periods of times but also he wrote some of his more important scientific contributions. After receiving private education in Glenlair, James was sent to Edinburgh Academy, where he spent five years. In 1847 he enrolled at Edinburgh University and, three years later, he went up to the University of Cambridge, the most influential center of physics at the time, where he graduated as Second Wrangler in the Mathematical Tripos of 1854 and he won the Smith Prize the same year. In the Smith\u2019s Prize examination, question 8 was on Stokes\u2019 Theorem. Some years later Maxwell would use this theorem in his work on the electromagnetic field.<\/p>\n

\"Statute<\/a>

Statute James Clerk Maxwell with his dog Toby at his feet and holding his colour wheel, Edinburgh (Scotland). Credit: A. Bel\u00e9ndez.<\/p><\/div>\n

In 1856, Maxwell got the Chair of Natural Philosophy at Marischal College, one of the two universities in Aberdeen at that time, where he spent four years. There he began his researches on colour theory and married Katherine Mary Dewar, daughter of the College Principal. Perhaps is less known that Maxwell was awarded the Adams Prize with an essay titled\u00a0On the stability of the motion of Saturn\u2019s rings<\/a><\/em>\u00a0which was published in 1859 and where he concluded that \u00abthe only system of rings which can exist is one composed of an indefinite number of unconnected particles, revolving around the planet with different velocities according to their respective distances.\u00bb Maxwell\u2019s work about the Saturn\u2019s rings was defined by\u00a0George Airy<\/a>, the Astronomer Royal, as \u00abone of the most remarkable applications of mathematics to physics that I have ever seen.\u00bb In 1895, sixteen years after Maxwell\u2019s death, the spectroscopic study made by the American astronomer\u00a0James Keeler<\/a>\u00a0confirmed the theory of Maxwell that Saturn\u2019s rings are made up of countless small objects.<\/p>\n

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A young James Clerk Maxwell holding his color wheel (Trinity College Library, Cambridge University). Credit: AIP Emilio Segre Visual Archives. Cr\u00e9ditos: James Clerk Maxwell Foundation.<\/p><\/div>\n

In 1860, he left Aberdeen to occupy another professorship in King\u2019s College, London. The five years Maxwell spent in London were probably the most creative in his life: colour vision and gas kinetic theories as well as the dynamical theory of the electromagnetic field. There he also produced\u00a0the world\u2019s first colour photography<\/a>, which was projected onto a screen at the Royal Institution in May of 1861. Maxwell was elected to the Royal Society three weeks later.<\/p>\n

Maxwell is also one of the founders of statistical physics. In 1860 he published\u00a0Illustrations of the dynamical theory of gases<\/em>\u00a0in which he needed only one page to obtain the distribution law of molecular speeds that bears his name. Maxwell was the first to formulate a statistical law that governs a physical phenomenon. Again, and as happened with his hypothesis of Saturn\u2019s rings, this law also was proven experimentally in this case by the German physicist\u00a0Otto Stern<\/a>\u00a0in 1920 using the molecular ray method.<\/p>\n

Maxwell resigned his King\u2019s professorship voluntarily in 1865, mid session, and went back to his Scottish estate in Glenlair. He wrote his\u00a0magnus opus<\/em>\u00a0there,\u00a0A Treatise on Electricity and Magnetism<\/em>, published in 1873, two volumes of more than 500 pages each, peak of nineteenth century physics and comparable to Newton\u2019s\u00a0Principia<\/em>, published almost two centuries before. In his\u00a0Treatise<\/em>\u00a0Maxwell manages to unify all known phenomena at the moment regarding electricity and magnetism.<\/p>\n

In 1871, Maxwell was appointed to take up the newly created Professorship of Experimental Physics at the University of Cambridge, and he became the first director of a new research centre, the Cavendish Laboratory, and became the first Cavendish Professor of Physics. Other directors who succeeded him were Lord Rayleigh, J. J. Thomson and Rutherford. To date 29 Nobel Prize winners have worked in the Cavendish Laboratory. He supervised every detail of the construction of the Laboratory. In 1877, Maxwell\u2019s health started to fail. He passed away due to an abdominal cancer on 5 November 1879. He was 48. Before dying, one of the things that most concerned to Maxwell was the future of his wife Katherine, whom he so loved.<\/p>\n

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Old Cavendish Laboratory, University of Cambridge.<\/p><\/div>\n

A Dynamical Theory of the Electromagnetic Field<\/strong><\/p>\n

Maxwell left us contributions to colour theory, optics, Saturn\u2019s rings, statics, dynamics, solids, instruments and statistical physics. However, his most important contributions were to electromagnetism. In 1856, he published\u00a0On Faraday\u2019s lines of force<\/em>; in 1861,\u00a0On physical lines of force.<\/em>\u00a0In these two articles he provided a mathematical explanation for Faraday\u2019s ideas on electrical and magnetic phenomena depending on the distribution of lines of force in space, definitively abandoning the classical doctrine of electrical and magnetic forces as actions at a distance. His mathematical theory included the aether, that \u00abmost subtle spirit\u00bb, as Newton described it. He studied electromagnetic interactions quite naturally in the context of an omnipresent aether. Maxwell stood firm that the aether was not a hypothetical entity, but a real one and, in fact, for physicists in the nineteenth century, aether was as real as the rocks supporting the Cavendish Laboratory.<\/p>\n

As has been mentioned at the beginning, in 1865 \u2013when Maxwell was 33\u2013 he published\u00a0A Dynamical Theory of the Electromagnetic Field<\/em>\u00a0\u2013probably his most important paper\u2013, where he presented a complete electromagnetic theory and which included twenty equations he called \u00abGeneral Equations of the Electromagnetic Field.\u00bb He links them to twenty variables governing the behaviour of electromagnetic interaction. The article is 53 pages long, divided in seven parts. His general equations, which summarised the experimental laws of electromagnetism, provide a complete theoretical basis for the treatment of classical electromagnetic phenomena. In 1884,\u00a0Oliver Heaviside<\/a>\u00a0rewrote the twenty equations of the electromagnetic field using vectors into the today\u2019s modern notation: the four equations of electromagnetic field. Since then, these equations were known as Hertz-Heaviside\u2019s equations or Maxwell-Hertz\u2019s equations, until 1940 when Albert Einstein coined the term \u00abMaxwell\u2019s equations\u00bb that we use today. The Austrian physicist\u00a0Ludwig Boltzmann<\/a>\u00a0considered them such beautiful equations in their simplicity and elegance that, with a quote from Goethe\u2019s Faust, he asked himself:\u00a0\u00abWar es ein Gott, der diese Zeichen schrieb?\u00bb<\/em>\u00a0(Was it a god who wrote these signs?).<\/p>\n

In the sixth part of his 1865 paper, \u00abElectromagnetic Theory of Light\u00bb, in which he refers to the paper titled\u00a0Thoughts on Ray-vibrations<\/em>\u00a0published by Faraday in 1846, saying \u00ab… the electromagnetic theory of light as proposed by him, is the same in substance as that which I have begun to develop in this paper, except that in 1846 there were no data to calculate the velocity of propagation.\u00bb Maxwell also concludes that \u00ablight and magnetism are affections of the same substance, and that light is an electromagnetic disturbance propagated through the field according to electromagnetic laws.\u00bb As Arthur Zajonc pointed out in his book\u00a0Catching the Light<\/em>, \u00abIn this single sentence, Maxwell proposed a profound change in our image of light, one is which light, electricity, and magnetism would now, and forever after, be entwined. Two arenas of physics, which to all outward appearances have nothing in common, were to be united.\u00bb When he wrote \u00abaffections of the same substance\u00bb, that substance was the\u00a0ether<\/em>. Although Maxwell\u2019s mathematical formulation did not require the\u00a0ether<\/em>, it was still omnipresent. He proved that the equations of the electromagnetic field could combine into a wave equation and suggested the existence of electromagnetic waves. Calculating the speed of propagation of these waves, he obtained the value of the speed of light, and concluded that it was an electromagnetic wave. Einstein referred to that crucial moment of Maxwell by pointing out: \u00abImagine [Maxwell\u2019s] feelings when the differential equations he had formulated proved to him that electromagnetic fields spread in the form of polarised waves, and at the speed of light! To few men in the world has such an experience been vouchsafed\u00bb Maxwell deduced that electromagnetic waves are transverse waves and he got what is now known as \u00abMaxwell relation\u00bb between the refractive index of a medium and the square root of its dielectric constant.<\/p>\n

In 1888, nine years after Maxwell\u2019s death,\u00a0Heinrich Hertz<\/a>\u00a0probed experimentally the existence of electromagnetics waves. This meant not only the confirmation of Maxwell\u2019s theory but also a win over telegraph engineers as William Preece, Engineer-in-Chief of the British General Post Office, which denied the applicability of Maxwellian physics to engineering. If Maxwell had lived in 1901 when the Italian engineer and Nobel Prize in Physics in 1909\u00a0Guglielmo Marconi<\/a>\u00a0made the first transatlantic radio communication across the Atlantic ocean, from Cornwall (England) to St. John\u2019s, in Newfoundland (Canada) \u2013using the electromagnetic waves whose existence Maxwell had predicted in 1865\u2013 perhaps Maxwell\u2019s fame would be far greater today.<\/p>\n

The significance of Maxwell\u2019s concept of electromagnetic waves, as subsequent history has shown, goes far beyond its application to light. Gamma rays, X rays, ultraviolet radiation, visible light, infrared radiation, microwaves and radio and television waves constitute the spectrum of electromagnetic waves, whose existence was predicted by Maxwell 150 years ago.<\/p>\n

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Electromagnetic spectrum with visible light highlighted (Wikipedia. Author: Philip Ronan).<\/p><\/div>\n

With his work,\u00a0Maxwell unified electricity, magnetism and light<\/strong>, which are known as\u00a0\u00abMaxwell\u2019s synthesis.\u00bb<\/strong>\u00a0Such a synthesis set a milestone in the history of the unification of forces that were so powerful that many nineteenth-century physicists thought the physical laws were already sufficiently comprehended. This led physicist and Nobel Prize in Physics in 1907\u00a0Albert Michelson<\/a>\u00a0to write in his book\u00a0Light and Their Uses<\/em>\u00a0published in 1903: \u00abThe more important fundamental laws and facts in physical sciences have all been discovered, and these are now so firmly established that the possibility of their ever being supplanted in consequence of new discoveries is exceedingly remote \u2026 Our future discoveries must be looked for in the sixth place of decimals.\u00bb Nothing could be further from the truth. In the first years of the twentieth century there were two Kuhnian paradigm shifts in physics: Planck\u2019s quantum theory (1900) and Einstein\u2019s theory of special relativity (1905), both consequences of Maxwell\u2019s electromagnetic theory and related to light, which laid the groundwork for these two revolutionary ideas. It is clear that Maxwell opened the doors for twentieth century physics.<\/p>\n

Maxwell’s Legacy<\/strong><\/p>\n

Although Maxwell\u2019s work on electromagnetism was essential, it had got some limitations, like trying to reconcile Newtonian mechanics and maxwellian electromagnetism. This problem was finally solved in 1905 when Einstein published his theory of special relativity. After Einstein\u2019s works, the luminiferous aether \u2013the focus of nineteenth century physics\u2013 was dead and buried. Even Albert Einstein recognised that his \u00abthe special theory of relativity owes its origins to Maxwell\u2019s equations.\u00bb In 1931, at the centenary of Maxwell\u2019s birth, in an article titled\u00a0Maxwell\u2019s influence on the development of the conception of physical reality<\/em>, Einstein claimed that \u00abone scientific epoch ended and another began with James Clerk Maxwell\u00bb and\u00a0\u00abthe work of James Clerk Maxwell changed the world forever.\u00bb<\/strong><\/p>\n

Richard Feynman<\/a>, Nobel Prize in Physics in 1965 for his work in\u00a0quantum electrodynamics<\/em>\u00a0(QED), the quantum theory of the electromagnetic field, pointed out: \u00abFrom a long view of the history of mankind, seen from, say, ten thousand years from now, there can be little doubt that the most significant event of the 19th century will be judged as Maxwell\u2019s discovery of the laws of electrodynamics.\u00bb<\/p>\n

MORE INFORMATION:<\/strong><\/p>\n

Augisto Bel\u00e9ndez, \u201cElectromagnetic Unification: 150th Anniversary of Maxwell\u2019s Equations\u201d, M\u00e8tode N\u00ba 84, Winter 2014\/15.<\/a><\/p>\n

J.\u00a0C. Maxwell, \u201cA Dynamical Theory of the Electromagnetic Field\u201d, Philosophical Transactions of the Royal Society of London, 155: 459-512 (1865).<\/a><\/p>\n

L. Campbell and W. Garnett, The life of James Clerk Maxwell (MacMillan and co., Londres 1882).<\/a><\/p>\n

N. Forbes and B. Mahon, Faraday, Maxwell, and the Electromagnetic Field: How two men revolutionized Physics (Prometheus Books, New York 2014).<\/a><\/p>\n

R. Flood, M. McCartney and A. Whitaker (eds.), James Clerk Maxwell. Perspectives on his Life and Work (Oxford University Press, Oxford 2014).<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

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