INTRODUCTION

One scientific epoch ended and another began with James Clerk Maxwell

Albert Einstein

 

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 nineteenth century will be judged as Maxwell’s discovery of the laws of electrodynamics.

Richard Feynmann

 

In 1861, James Clerk Maxwell had a scientific idea that was as profound as any work of philosophy, as beautiful as any painting, and more powerful than any act of politics or war. Nothing would be the same again.

In the middle of the nineteenth century the world’s best physicists had been searching long and hard for a key to the great mystery of electricity and magnetism. The two phenomena seemed to be inextricably linked but the ultimate nature of the linkage was subtle and obscure, defying all attempts to winkle it out. Then Maxwell found the answer with as pure a shaft of genius as has ever been seen.

He made the astounding prediction that fleeting electric currents could exist not only in conductors but in all materials, and even in empty space. Here was the missing part of the linkage; now everything fitted into a complete and beautiful theory of electromagnetism.

This was not all. The theory predicted that every time a magnet jiggled, or an electric current changed, a wave of energy would spread out into space like a ripple on a pond. Maxwell calculated the speed of the waves and it turned out to be the very speed at which light had been measured. At a stroke, he had united electricity, magnetism and light. Moreover, visible light was only a small band in a vast range of possible waves, which all travelled at the same speed but vibrated at different frequencies.

Maxwell’s ideas were so different from anything that had gone before that most of his contemporaries were bemused; even some admirers thought he was indulging in a wild fantasy. No proof came until a quarter of a century later, when Heinrich Hertz produced waves from a spark-gap source and detected them.

Over the past 100 years we have learnt to use Maxwell’s waves to send information over great and small distances in tiny fractions of a second. Today we can scarcely imagine a world without radio, television and radar. His brainchild has changed our lives profoundly and irrevocably.

Maxwell’s theory is now an established law of nature, one of the central pillars of our understanding of the universe. It opened the way to the two great triumphs of twentieth century physics, relativity and quantum theory, and survived both of those violent revolutions completely intact. As another great physicist, Max Planck, put it, the theory must be numbered among the greatest of all intellectual achievements. But its results are now so closely woven into the fabric of our daily lives that most of us take it wholly for granted, its author unacknowledged.

What makes the situation still more poignant is that Maxwell would be among the world’s greatest scientists even if he had never set to work on electricity and magnetism. His influence is everywhere. He introduced statistical methods into physics; now they are used as a matter of course. He demonstrated the principle by which we see colours and took the world’s first colour photograph. His whimsical creation, Maxwell’s demon—a molecule-sized creature who could make heat flow from a cold gas to a hot one—was the first effective scientific thought experiment, a technique Einstein later made his own. It posed questions that perplexed scientists for 60 years and stimulated the creation of information theory, which underpins our communications and computing. He wrote a paper on automatic control systems many years before anyone else gave thought to the subject; it became the foundation of modern control theory and cybernetics. He designed the Cavendish Laboratory and, as its founding Director, started a brilliant revival of Cambridge’s scientific tradition which led on to the discoveries of the electron and the structure of DNA.

Some of his work gave direct practical help to engineers. He showed how to use polarised light to reveal strain patterns in a structure and invented a neat and powerful graphical method for calculating the forces in any framework; both techniques became standard engineering practice. He was also the first to suggest using a centrifuge to separate gases.

Maxwell was born in 1831 and lived for 48 years. A native Scotsman, he spent about half of his working life in England. From his earliest days he was fascinated by the world and determined to find out how it worked. Like all parents, his were assailed with questions, but to be interrogated by 3 year-old James must have been an experience of a different order. Everything that moved, shone or made a noise drew the question ‘What’s the go o’ that?’ and, if he was not satisfied, the follow-up ‘but what’s the particular go of it?’. A casual comment about a blue stone brought the response ‘but how d’ye know it’s blue?’. Maxwell’s childish curiosity stayed with him and he spent most of his adult life trying to work out the ‘go’ of things. At the task of unravelling nature’s deep secrets he was supreme.

Those in the know honour Maxwell alongside Newton and Einstein, yet most of us have never heard of him. This is an injustice and a mystery but most of all it is our own great loss. One excellent reason for telling this story is to try to gain Maxwell a little of the public recognition he so clearly deserves, but a much better one is to try to make good the loss. His was a life for all of us to enjoy. He was not only a consummate scientist but a man of extraordinary personal charm and generous spirit: inspiring, entertaining and entirely without vanity. His friends loved and admired him in equal measure and felt better for knowing him. Perhaps we can share a tiny part of that experience.