James Clerk Maxwell statue

Book interview: Brian Clegg, ‘Professor Maxwell’s Duplicitous Demon’

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Although nowhere near as well known as Einstein or Newton, James Clerk Maxwell was one of the greatest scientists, beating a path to 21st century physics. Brian Clegg, author of a new biography of Maxwell, explains why.

“James Clerk Maxwell’s is a lovely story about someone that’s not well known to the general public. Maxwell should be up there with Newton and Einstein,” says Brian Clegg, author of a superb new biography of one of the greatest scientists of the 19th or any other century. For Clegg, the reason Maxwell should be better known is simply that the work conducted by the Victorian scientist laid the foundations for what could be achieved in 20th-century physics.

To support his point, Clegg quotes theoretical physicist Richard Feynman: “From 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’s discovery of the laws of electrodynamics.”

Clegg, who is a prolific writer of highly respected books, says that his motivation for writing ‘Professor Maxwell’s Duplicitous Demon’ stems from more than just a sense of injustice that his subject lacks recognition. “In virtually every book I mention Maxwell. Also, there’s a lot of work being done on experimental versions of Maxwell’s ‘demon’ on a quantum level.” The term was coined by Lord Kelvin for a thought experiment devised by Maxwell to challenge the second law of thermodynamics, “that is generally thought of as being the most fundamental of physical laws”.

The demon provides a character in Clegg’s biography, which is distinguished not least because it contains a sustained literary device. The demon “acts as an intermediary between Maxwell himself and the reader”. And he’s a good enough writer to pull it off. There are times, especially in the demonic interludes that are written from the perspective of an anthropomorphised incarnation of the thought experiment, when we appear to be straying into a metaphysical territory more usually associated with Philip Pullman’s ‘His Dark Materials’ trilogy. This all adds up to a superbly entertaining biography that doesn’t underestimate its readership. ‘Professor Maxwell’s Duplicitous Demon’ is a substantial and thought-provoking read, light years away from those irritating books that simplify high concepts in the name of popular science.

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‘Professor Maxwell’s Duplicitous Demon’

According to Brian Clegg, James Clerk Maxwell is a great in the world of physics, notable for his work in statistical mechanics and electromagnetism. Without Maxwell, it’s arguable that 20th century physics would have been different. ‘Professor Maxwell’s Duplicitous Demon’ is Clegg’s biography of the great man who, in laying down the bedrock of modern physics, worked on colour perception, the behaviour of gases, as well as laying the groundwork for everything from Einstein’s theory of special relativity to modern electronics. He set up one of the most enduring challenges in physics – the Maxwell’s Demon of the book’s title is a tiny, but thoroughly disruptive, thought experiment that suggests the second law of thermodynamics can be broken. Brilliant stuff.

It’s also a good-natured and, at times, fun read. These are characteristics of Maxwell himself. “When you look at some of the historical physicists, there’s a distinct lack of sense of humour,” says Clegg. “Someone like Newton, for instance, is not exactly known for his laughs. But if you read Maxwell’s letters, it’s clear that his sense of humour was central to who he was.” Clegg also wanted to make Maxwell “approachable, giving a slightly different and hopefully more edgy viewpoint to the non-technical reader”.

These days we tend to think that for the prodigious young talent that was Maxwell greatness was an inevitability. But Clegg isn’t so sure. “It’s certainly true to some extent that from an early age he would have had some interest in nature and science in a broad sense. But it wasn’t necessarily obvious that he was to become a theoretical physicist,” partially because the somewhat feral young Maxwell spent more time exploring the rivers and wilds of the family estate in Scotland than educating himself. “But he was encouraged to be inquisitive,” and one of the products of this inquisitiveness was that he was publishing scientific papers from the age of 14, his first on the mathematics of shapes. “He was also playing around with all sorts of thing in his home laboratory, which is interesting because at the time physics was a very theoretical concept.” Back in the 1840s there “weren’t many physics labs, even in the universities”.

In terms of Maxwell’s scientific legacy, “there are two big things and several medium-sized things. What’s always mentioned is the statistical mechanics – the nature of gases deduced from the statistical behaviour of molecules, working out how they interact with one another. This was quite advanced because at that time people weren’t even sure that atoms existed.” But biggest of all was electromagnetism “where he worked out mathematically the relationship between magnetism and electricity, and from that deduced that light was an electromagnetic wave”.

Other projects included the production of the first colour photograph based on his “interest in colour vision and colour mixing, and how all that worked. He also worked on viscosity. He worked on electrical resistance and pretty much defined the ohm as a value. He worked on governors that would lead to feedback cybernetics.

“There’s a huge range. Some technologies we’re working on today are founded on Maxwell’s achievements. You can’t say that without Maxwell certain things might never have happened. But on the other hand, in some cases he was well ahead of the game. What’s really interesting is that these days you simply wouldn’t get a scientist on this kind of level that is both a theoretician and an experiment physicist” – a fact that Clegg attributes to Maxwell acquiring both a Scottish and English education.

At the time the Scottish universities “treated physics in a practical way and were good on the experimental side, while the University of Cambridge, where Maxwell went, was totally focused on maths. Everybody that went to Cambridge had to do maths.” The fact is, says Clegg, that unless you had education in both places, you couldn’t get the combination of theory and practice. Clegg reminds me that part of Maxwell’s transformative effect on science was that he founded the Cavendish Laboratory in Cambridge that “was to have a huge impact on 20th-century physics”.

Clegg comes back to the idea that a scientific biography must be more than a list of technical accomplishments. “There’s also a personal side to this. Maxwell wrote poetry and had an impressive sense of humour. He was very much into science communication and education for working class people. This is central to our understanding of his character. Compared with many scientists I’ve written about, Maxwell is someone I wouldn’t mind going out for a drink with and having a chat.”

‘Professor Maxwell’s Duplicitous Demon’ by Brian Clegg is published by Icon, £16.99


Maxwell’s colour thinking

Maxwell notes that some individuals have a ‘peculiar inability’ to distinguish certain colours – his work went hand in hand with a deep interest in those who were colour blind, suffering from ‘Daltonism’ as it was often known then after the chemist John Dalton, who suffered from the condition and was one of the first to study it scientifically. Maxwell records that the most interesting result is that ‘different eyes in similar circumstances agree to the most minute accuracy ... while the same eyes in different lights give different results.’

So, he had discovered, our perception of colour is strongly affected by lighting, but is remarkably consistent between individuals who have normal colour vision. But Maxwell was not willing to expand his observations too far from the small sample he originally had access to. He noted: ‘These results can be completely verified only by a large number of observations.’ For the rest of his working life, he would invite visitors to try out colour mixing devices to widen his sample, and would ask friends to take the test and to bring anyone they knew who didn’t see colour the same as the majority.

Maxwell followed up his initial manuscript on the subject with a paper presented to the Royal Society of Edinburgh, where he brought out further his idea that colour blindness was typically caused by one of three colour systems in the eye being defective. He felt it should be possible to make combinations of colour on his colour top (or wheel), which identified what sensitivities were missing in people’s colour perception. Maxwell would never know the practical importance of his work that allowed us to produce the colour screens we now use on TVs, computers and phones.

Edited extract from ‘Professor Maxwell’s Duplicitous Demon’ by Brian Clegg, reproduced with permission.

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