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Friday, August 29, 2014

Reading List: The Man Who Changed Everything

Mahon, Basil. The Man Who Changed Everything. Chichester, UK: John Wiley & Sons, 2003. ISBN 978-0-470-86171-4.
In the 19th century, science in general and physics in particular grew up, assuming their modern form which is still recognisable today. At the start of the century, the word “scientist” was not yet in use, and the natural philosophers of the time were often amateurs. University research in the sciences, particularly in Britain, was rare. Those working in the sciences were often occupied by cataloguing natural phenomena, and apart from Newton's monumental achievements, few people focussed on discovering mathematical laws to explain the new physical phenomena which were being discovered such as electricity and magnetism.

One person, James Clerk Maxwell, was largely responsible for creating the way modern science is done and the way we think about theories of physics, while simultaneously restoring Britain's standing in physics compared to work on the Continent, and he created an institution which would continue to do important work from the time of his early death until the present day. While every physicist and electrical engineer knows of Maxwell and his work, he is largely unknown to the general public, and even those who are aware of his seminal work in electromagnetism may be unaware of the extent his footprints are found all over the edifice of 19th century physics.

Maxwell was born in 1831 to a Scottish lawyer, John Clerk, and his wife Frances Cay. Clerk subsequently inherited a country estate, and added “Maxwell” to his name in honour of the noble relatives from whom he inherited it. His son's first name, then was “James” and his surname “Clerk Maxwell”: this is why his full name is always used instead of “James Maxwell”. From childhood, James was curious about everything he encountered, and instead of asking “Why?” over and over like many children, he drove his parents to distraction with “What's the go o' that?”. His father did not consider science a suitable occupation for his son and tried to direct him toward the law, but James's curiosity did not extend to legal tomes and he concentrated on topics that interested him. He published his first scientific paper, on curves with more than two foci, at the age of 14. He pursued his scientific education first at the University of Edinburgh and later at Cambridge, where he graduated in 1854 with a degree in mathematics. He came in second in the prestigious Tripos examination, earning the title of Second Wrangler.

Maxwell was now free to begin his independent research, and he turned to the problem of human colour vision. It had been established that colour vision worked by detecting the mixture of three primary colours, but Maxwell was the first to discover that these primaries were red, green, and blue, and that by mixing them in the correct proportion, white would be produced. This was a matter to which Maxwell would return repeatedly during his life.

In 1856 he accepted an appointment as a full professor and department head at Marischal College, in Aberdeen Scotland. In 1857, the topic for the prestigious Adams Prize was the nature of the rings of Saturn. Maxwell's submission was a tour de force which proved that the rings could not be either solid nor a liquid, and hence had to be made of an enormous number of individually orbiting bodies. Maxwell was awarded the prize, the significance of which was magnified by the fact that his was the only submission: all of the others who aspired to solve the problem had abandoned it as too difficult.

Maxwell's next post was at King's College London, where he investigated the properties of gases and strengthened the evidence for the molecular theory of gases. It was here that he first undertook to explain the relationship between electricity and magnetism which had been discovered by Michael Faraday. Working in the old style of physics, he constructed an intricate mechanical thought experiment model which might explain the lines of force that Faraday had introduced but which many scientists thought were mystical mumbo-jumbo. Maxwell believed the alternative of action at a distance without any intermediate mechanism was wrong, and was able, with his model, to explain the phenomenon of rotation of the plane of polarisation of light by a magnetic field, which had been discovered by Faraday. While at King's College, to demonstrate his theory of colour vision, he took and displayed the first colour photograph.

Maxwell's greatest scientific achievement was done while living the life of a country gentleman at his estate, Glenair. In his textbook, A Treatise on Electricity and Magnetism, he presented his famous equations which showed that electricity and magnetism were two aspects of the same phenomenon. This was the first of the great unifications of physical laws which have continued to the present day. But that isn't all they showed. The speed of light appeared as a conversion factor between the units of electricity and magnetism, and the equations allowed solutions of waves oscillating between an electric and magnetic field which could propagate through empty space at the speed of light. It was compelling to deduce that light was just such an electromagnetic wave, and that waves of other frequencies outside the visual range must exist. Thus was laid the foundation of wireless communication, X-rays, and gamma rays. The speed of light is a constant in Maxwell's equations, not depending upon the motion of the observer. This appears to conflict with Newton's laws of mechanics, and it was not until Einstein's 1905 paper on special relativity that the mystery would be resolved. In essence, faced with a dispute between Newton and Maxwell, Einstein decided to bet on Maxwell, and he chose wisely. Finally, when you look at Maxwell's equations (in their modern form, using the notation of vector calculus), they appear lopsided. While they unify electricity and magnetism, the symmetry is imperfect in that while a moving electric charge generates a magnetic field, there is no magnetic charge which, when moved, generates an electric field. Such a charge would be a magnetic monopole, and despite extensive experimental searches, none has ever been found. The existence of monopoles would make Maxwell's equations even more beautiful, but sometimes nature doesn't care about that. By all evidence to date, Maxwell got it right.

In 1871 Maxwell came out of retirement to accept a professorship at Cambridge and found the Cavendish Laboratory, which would focus on experimental science and elevate Cambridge to world-class status in the field. To date, 29 Nobel Prizes have been awarded for work done at the Cavendish.

Maxwell's theoretical and experimental work on heat and gases revealed discrepancies which were not explained until the development of quantum theory in the 20th century. His suggestion of Maxwell's demon posed a deep puzzle in the foundations of thermodynamics which eventually, a century later, showed the deep connections between information theory and statistical mechanics. His practical work on automatic governors for steam engines foreshadowed what we now call control theory. He played a key part in the development of the units we use for electrical quantities.

By all accounts Maxwell was a modest, generous, and well-mannered man. He wrote whimsical poetry, discussed a multitude of topics (although he had little interest in politics), was an enthusiastic horseman and athlete (he would swim in the sea off Scotland in the winter), and was happily married, with his wife Katherine an active participant in his experiments. All his life, he supported general education in science, founding a working men's college in Cambridge and lecturing at such colleges throughout his career.

Maxwell lived only 48 years—he died in 1879 of the same cancer which had killed his mother when he was only eight years old. When he fell ill, he was engaged in a variety of research while presiding at the Cavendish Laboratory. We shall never know what he might have done had he been granted another two decades.

Apart from the significant achievements Maxwell made in a wide variety of fields, he changed the way physicists look at, describe, and think about natural phenomena. After using a mental model to explore electromagnetism, he discarded it in favour of a mathematical description of its behaviour. There is no theory behind Maxwell's equations: the equations are the theory. To the extent they produce the correct results when experimental conditions are plugged in, and predict new phenomena which are subsequently confirmed by experiment, they are valuable. If they err, they should be supplanted by something more precise. But they say nothing about what is really going on—they only seek to model what happens when you do experiments. Today, we are so accustomed to working with theories of this kind: quantum mechanics, special and general relativity, and the standard model of particle physics, that we don't think much about it, but it was revolutionary in Maxwell's time. His mathematical approach, like Newton's, eschewed explanation in favour of prediction: “We have no idea how it works, but here's what will happen if you do this experiment.” This is perhaps Maxwell's greatest legacy.

This is an excellent scientific biography of Maxwell which also gives the reader a sense of the man. He was such a quintessentially normal person there aren't a lot of amusing anecdotes to relate. He loved life, loved his work, cherished his friends, and discovered the scientific foundations of the technologies which allow you to read this. In the Kindle edition, at least as read on an iPad, the text appears in a curious, spidery, almost vintage, font in which periods are difficult to distinguish from commas. Numbers sometimes have spurious spaces embedded within them, and the index cites pages in the print edition which are useless since the Kindle edition does not include real page numbers.

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