Maxwell Writes the Rules

James Clerk Maxwell unified electricity and magnetism into one complete theory. His original 19th-century formulation was not the neat four-equation set students memorize today; that compact vector form was later distilled from Maxwell's work by Oliver Heaviside and others.

The result was revolutionary: changing electric fields create magnetic fields, changing magnetic fields create electric fields, and light itself is an electromagnetic wave.

His equations predicted that changing electric fields create magnetic fields, and changing magnetic fields create electric fields — a self-sustaining wave propagating through space at 300,000 km/s. That number matched the measured speed of light exactly.