James Clerk Maxwell
James Clerk Maxwell (1831 - 1879) "The numbers may be said to rule the whole world of quantity, and the four rules of arithmetic may be regarded as the complete equipment of the mathematician." Everyone's a fan of Albert Einstein, and for good reason: He invented at least four new fields of physics, spun a brand-new theory of gravity out of the fabric of his own imagination, and taught us the true nature of time and space. But who was Einstein a fan of? James Clerk Maxwell. Who? Oh, he's only the scientist responsible for explaining the forces behind the radio in your car, the magnets on your fridge, the heat of a warm summer day and the charge on a battery. Most people aren't familiar with Maxwell, a 19th-century Scottish scientist and polymath. Yet he was perhaps the single greatest scientist of his generation and revolutionized physics in a way nobody was expecting. In fact, it took years for Maxwell's peers to realize just how awesome — and right — he was. At the time, one of the great focuses of scientific interest was the strange and perplexing properties of electricity and magnetism. While the two forces had been known to humanity for millennia, the more scientists studied these forces, the weirder they seemed. Ancient people knew that certain animals, like electric eels, could shock you if you touched them and that certain substances, like amber, could attract things if you rubbed them. They knew that lightning could start fires. They had found seemingly magical rocks, called lodestones, that could attract bits of metal. And they had mastered the use of the compass, albeit without understanding how it worked. By the time Maxwell stepped in, a wide variety of experiments had expanded on the weirdness of these forces. Scientists like Benjamin Franklin had discovered that the electricity from lightning could be stored. Luigi Galvani found that zapping living organisms with electricity caused them to move. Meanwhile, French scientists found that electricity moving down a wire could attract — or repel, depending on the direction of the flow — another wire and that electrified spheres could attract or repel with a strength proportional to the square of their separation. Most bewilderingly, there seemed to be a strange link between electricity and magnetism. Electrified wires could deflect the motion of a compass. Starting the flow of electricity in one wire could spur the flow of electricity in another, even if the wires weren't connected. Waving a magnet around could generate electricity. All of this was absolutely fascinating, but nobody had any idea what was going on.
Then Maxwell came along. He had heard about all this electricity and magnetism confusion while he was working on another problem: how color vision works. (Indeed, he invented the color photograph.) In just a few years, Maxwell envisioned the physics and mathematics needed to explain all of the experiments relating to electricity and magnetism. To do it, he just had to think like a future scientist. Today, modern physics is based on the concept of the field, an entity that spans all of space and time and tells other objects how to move. While Maxwell wasn't the first to envision such a field, he was the first to put it to work and turn it from a convenient mathematical trick into a real physical entity. For example, Maxwell envisioned the forces of electricity and magnetism to be carried and communicated by electric and magnetic fields. Maxwell said an electric charge would produce an electric field that surrounded it. Any other charges could sense this field, and based on the strength and direction of the field, it would know how to respond to the force of the original charge. The same went for the magnetic field, and Maxwell took it one step further. He realized that electric and magnetic fields are two sides of the same coin: Electricity and magnetism weren't two separate, distinct forces, but merely two expressions of the same, unified electromagnetic force. You can't think about electricity without also thinking about magnetism, and vice versa. Let there be light Maxwell's insights took the form of 20 interconnected equations, which, a few years later, were reduced to four equations of electromagnetism that are still taught to scientists and engineers today. His revolution followed Isaac Newton's first unification of physics, in which Earth's gravity was joined with the gravity of the heavens under a single law, and Maxwell's equations became known as the second great unification in physics. Maxwell's insight was huge — who would have guessed that electricity and magnetism weren't just related, but the same? Modern physics is all about finding single unifying principles to describe vast areas of natural phenomena, and Maxwell took the unification party to the next level. But Maxwell didn't stop there. He realized that changing electric fields could induce magnetic fields, and vice versa. So he immediately began to wonder if such a setup could be self-reinforcing, wherein a changing electric field would create a changing magnetic field, which could then create a changing electric field and so on. Maxwell realized that this would be a wave — a wave of electromagnetism. He set about calculating the speed of these electromagnetic waves, using the strengths of the forces of electricity and magnetism, and out popped … the speed of light. By introducing the concept of the field to the analysis of electricity and magnetism, Maxwell discovered that light — in all its forms, from the infrared, to radio waves, to the colors of the rainbow — was really waves of electromagnetic radiation. With one set of equations, one brilliant leap of intuition and insight, Maxwell united three great realms of physics: electricity, magnetism and optics. No wonder Einstein admired him. Note: Electromagnetism His paper On Physical Lines of Force—written over the course of two years (1861-1862) and ultimately published in several parts—introduced his pivotal theory of electromagnetism. Among the tenets of his theory were (1) that electromagnetic waves travel at the speed of light, and (2) that light exists in the same medium as electric and magnetic phenomena. In 1865, Maxwell resigned from King’s College and proceeded to continue writing: A Dynamical Theory of the Electromagnetic Field during the year of his resignation; On reciprocal figures, frames and diagrams of forces in 1870; Theory of Heat in 1871; and Matter and Motion in 1876. In 1871, Maxwell became the Cavendish Professor of Physics at Cambridge, a position that put him in charge of the work conducted in the Cavendish Laboratory. The 1873 publication of A Treatise on Electricity and Magnetism, meanwhile, produced the fullest explanation yet of Maxwell’s four partial different equations, which would go on to be a major influence on Albert Einstein’s theory of relativity. On November 5, 1879, after a period of sustained illness, Maxwell died—at the age of 48—from abdominal cancer. Considered one of the greatest scientific minds the world has ever seen—on the order of Einstein and Isaac Newton—Maxwell and his contributions extend beyond the realm of electromagnetic theory to include: an acclaimed study of the dynamics of Saturn’s rings; the somewhat accidental, although still important, capturing of the first color photograph; and his kinetic theory of gases, which led to a law relating to the distribution of molecular velocities. Still, the most crucial findings of his electromagnetic theory—that light is an electromagnetic wave, that electric and magnetic fields travel in the form of waves at the speed of light, that radio waves can travel through space—constitute his most important legacy. Nothing sums up the monumental achievement of Maxwell’s life work as well as these words from Einstein himself: “This change in the conception of reality is the most profound and the most fruitful that physics has experienced since the time of Newton.”
