James Clerk Maxwell

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James Clerk Maxwell – from Popular Science Monthly Volume 17, 1880.  Public Domain

James Clerk Maxwell is a Scottish theoretical physicist who is best known for formulating what became known as Maxwell’s equations, the series of equations that codifies the relationships between electricity and magnetism within electromagnetism.  

Basic Information

Birthdate: June 13, 1831

Birth location: Edinburgh, Scotland

Date of death: November 5, 1879

Early Life, Education, & Career

James Clerk Maxwell studied first at the University of Edinburgh (1847-1850) and then on the University of Cambridge (1850-1856).

He graduated from the University of Cambridge in 1854 with a degree in mathematics, but remained at the university for two additional years on a fellowship. In 1856, he obtained a professorship at Marischal College in Aberdeen, where he remained until 1860, at which point he moved on to King’s College, London. He retired from King’s College in 1965, though he remained academically active and wrote a number of books. He returned to Cambridge in 1871 as the first Cavendish Professor of Physics, where his duties included overseeing the creation of the Cavendish Laboratory (a research laboratory that, as of the time of this writing in summer 2015, has resulted in a total of 29 Nobel Prizes in Physics).

Though he is best known for his work studying electromagnetism and light, he also contributed insights into the field of thermodynamics, including a study of the kinetic theory of gases.

Developing Maxwell’s Equations

Maxwell studied intently the insights into electromagnetism developed by Michael Faraday, including his concept of lines of force.

With his more rigorous mathematical approach to the field, Maxwell was able to solidify this intuitive concept into a series of 20 equations with 20 variables, which he published in 1861. Over the following decade, he would refine his understanding, ultimately writing his Maxwell’s equations as four partial differential equations in his 1873 book A Treatise on Electricity and Magnetism. (They have been refined a bit in the years since then.)

In the course of this work, Maxwell realized that both electricity and magnetism moved at approximately the speed of light. This suggested to him that light itself was electromagnetic in nature, setting the groundwork for the concept of the electromagnetic spectrum of light. Indeed, he extensively studied the field of optics, specifically as it related to colors (and the perception of color by humans) in the visible spectrum of light.

Consequences of Maxwell’s Equations

Maxwell’s key insight was that light could be described as waves moving through space at the speed of light. This seemed to definitively establish that light behaved as a wave, confirming the explanation that most readily explained Thomas Young’s double-slit experiment. The problem with this wave explanation of light, however, was that the common understanding of waves at the time was that it required a medium to pass through (something had to “do the waving”). This led to the search for the luminiferous ether as a medium for light to travel through. A search that ultimately failed to discover the luminiferous ether.

When Albert Einstein looked at Maxwell’s equations, he realized that a key feature of them was that the light moved at the speed of light. If light indeed moved through a medium, it would move at speeds relative to the medium rather than at a single speed. He assumed that the light moved at a single fixed speed, and this became one of the core postulates of his theory of relativity.

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