A Dynamical Theory of the Electromagnetic Field
Maxwell left us contributions to colour theory, optics, Saturn’s rings, statics, dynamics, solids, instruments and statistical physics. However, his most important contributions were to electromagnetism. In 1856, he published On Faraday’s lines of force; in 1861, On physical lines of force. In these two articles he provided a mathematical explanation for Faraday’s 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 «most subtle spirit», 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.
On June 13, but in 1831 the Scottish physicist James Clerk Maxwell was born. In 1865, one hundred and fifty years ago, he published an article titled A Dynamical Theory of the Electromagnetic Field, which not only included the electromagnetic field equations (today known as «Maxwell’s equations»), but also predicted the existence of electromagnetic waves moving at the speed of light, and presented the electromagnetic theory of light. In this article he stated: «it seems we have strong reason to conclude that light itself (including radiant heat, and other radiations if any) is an electromagnetic disturbance in the form of waves propagated through the electromagnetic field according to electromagnetic laws». He was not wrong. Then, in 2015, we celebrate the 150th anniversary of the electromagnetic theory of light, which is one of the milestones commemorated in the International Year of Light and Light-Based Technologies (IYL 2015).
Statute James Clerk Maxwell with his dog Toby at his feet and holding his colour wheel, Edinburgh (Scotland). Credit: A. Beléndez.
Why does Blue Nile musician PJ Moore feel the need to Crowdfund an electronic oratorio for James Clerk Maxwell at this year’s Edinburgh Fringe?
Well, here’s a true story……
Artwork for In Time of Light. Credit: “Portrait of James Clerk Maxwell FRSE (1831–1879), after R H Campbell, reproduced by permission of the Royal Society of Edinburgh.
Next time you turn on your TV, think of James Clerk Maxwell. In one of the greatest feats of human thought he predicted the electromagnetic waves that bring the signal from the transmitter to your set. He also provided the means of producing the coloured image on your screen by showing that any colour can be made by combining red, green, and blue light in the appropriate proportions.
He was born in 1831 into a distinguished Scottish family and went to a top school in Edinburgh before studying at both Edinburgh and Cambridge Universities. In an astonishing and short career (he died aged 48), Maxwell made groundbreaking discoveries in every branch of physics that he turned his hand to. But in the International Year of Light 2015 it is fitting that we celebrate in particular his discoveries about light: not only his electromagnetic theory, first published 150 years ago, but also his demonstration of the way we see colours.