#3 – James Clerk Maxwell

James Clerk Maxwell is my favorite physicist. This site takes its name from a wise thing he once said: “In every branch of knowledge the progress is proportional to the amount of facts on which to build, and therefore to the facility of obtaining data.” For all the volumes written about the philosophy of science, that sums it up pretty well. Is it built on observable facts and empirical data? If so, it’s science. Otherwise it’s not. Anyone, however, can come up with a clever thing to say. Almost no one in history has come up with as many brilliant contributions to the modern world as Maxwell. I’m going to let a few more brilliant men do some of the work for me, as whatever I say is not really going to cut it when describing this level of accomplishment.

*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. The American Civil War will pale into provincial insignificance in comparison with this important scientific event of the same decade. *

– Richard Feynman

He was born in 1831 and had a fairly standard childhood. It was always clear he was a particularly bright child. By the time Maxwell was 16, he was enrolled at the University of Edinburgh, where he conducted experiments involving the polarization of light. No one yet new was polarization really was. For that matter, no one knew what light was either. After leaving Edinburgh, he went to Cambridge where he began to make a name for himself as a mathematician of considerable talent. He published his studies of the properties of certain curves and began his study of color and light. His work attracted great interest, he lectured at the Royal Society, and shot up the ranks and became the chair of Natural Philosophy at Marischal College in 1856. Natural philosophy was in those days the name for what we’d today call the physical sciences.

He set to work fulfilling his new responsibilities, and among his first accomplishments was a mathematical exploration of the properties of the rings of Saturn. He showed that there was really no possibility other than that the rings were composed of small independent particles orbiting the planet, and about a century later this was proved by the flight of the Voyager probes.

Most of Maxwell’s fame very justifiably derives from his contributions to electromagnetism, but almost casually he made great advances in a number of other fields. There’s thermodynamics in the form of the Maxwell-Boltzmann distribution and the Maxwell relations. There’s some of the first real treatments of dimensional analysis. There’s foundational papers in control theory. He took the first color photograph. You name it in physics; Maxwell may well have been involved.

*Maxwell’s equations have had a greater impact on human history than any ten presidents.*

– Carl Sagan

Maxwell was the first to unify the theory of electricity and magnetism in one coherent whole by writing down these four equations, for each of which I’ll give a very brief synopsis:

Electric charges create electric fields.

Magnetic charges would create magnetic fields if there were such thing as magnetic charges. But there aren’t.

A changing magnetic field creates an electric field without the need for charge to be involved.

A changing electric field creates a magnetic field without the need for charge to be involved. Electric currents also create magnetic fields.

Now let me dispel some of the “physics legend” version of this story. Maxwell didn’t write these equations in this modern form. He wrote them in a version which more or less wrote the curl operator in a less compact way involving each axis separately. Heaviside first wrote them in their modern form. And Maxwell didn’t invent these equations individually, he only added the electric field term to the last equation.

That, however, was more than enough. With that modification he was able to find the wave solutions to this equation and deduce that electric and magnetic fields could mutually produce each other and propagate through space. He found that the theory predicted those waves would travel at about 300,000,000 m/s, which happened to be the speed of light. This let him make the bold inference that light *is* just electric and magnetic fields interacting in a particular way. As indeed it is.

*The work of James Clerk Maxwell changed the world forever.*

– Albert Einstein

Maxwell was ahead of his time. Unlike Newton’s laws which require an absolute reference frame, Maxwell’s equations keep the same form in every inertial frame. They don’t even require modification to work with Einstein’s special relativity. Maxwell wrote the first relativistic field theory and didn’t even know it. Today we can express this more clearly (if you’re familiar with tensor notation) by boiling down his four equations into two.

For all that and more, James Clerk Maxwell takes a well-deserved place among the pantheon of the true greats.

*The list so far (click the category name for links):
3. Maxwell
4. Faraday
5. Feynman
6. Rutherford
7. Schrodinger
8. Dirac
9. Thomson
10. Pauli*

*Not-strictly-physicist honorable mentions:
Galileo
Noether
*