James Clerk Maxwell formulated the classical electromagnetic theory that unified electricity, magnetism, and light.
Maxwell developed a set of equations describing electric fields, magnetic fields, electric charges, and currents. His work showed that changing electric fields can produce magnetic fields and changing magnetic fields can produce electric fields. The resulting self-propagating disturbances travel at the speed of light, leading Maxwell to identify light as an electromagnetic wave.
Maxwell published his major electromagnetic theory in the 1860s, building on experimental and mathematical work by scientists including Michael Faraday, André-Marie Ampère, and Carl Friedrich Gauss. His theory predicted electromagnetic waves before Heinrich Hertz detected radio waves experimentally in the late 1880s.
Maxwell’s equations remain central to classical physics and electrical engineering. They describe phenomena ranging from antennas and optics to waveguides and transmission lines. They do not replace quantum electrodynamics for microscopic interactions, but they are highly accurate for ordinary macroscopic electromagnetic systems.