Electromagnetism

By 1861, physicists had three separate, well-tested subjects on their hands: electricity, magnetism, and optics. Each had its own laws, its own instruments, its own experts. James Clerk Maxwell looked at Michael Faraday’s rough, unmathematical picture of invisible “lines of force” filling the space around a magnet or a charge, translated it into a rigorous…

For most of human history, electricity was a party trick. Rub amber with fur and it would tug at bits of straw; that was about the extent of anyone’s understanding. By 1873, electricity and magnetism had merged into a single mathematical theory that also explained light itself. The path between those two points runs through…