James Clerk Maxwell

James Clerk Maxwell formulated the classical theory of electromagnetism, synthesizing the work of Faraday, Gauss, and Ampère into a set of four elegant differential equations. His 'A Dynamical Theory of the Electromagnetic Field' (1864) demonstrated that electricity, magnetism, and light are all manifestations of the same phenomenon: electromagnetic waves. He calculated that these waves travel at the speed of light, revealing light itself as an electromagnetic wave. This unification is considered one of the greatest achievements of 19th-century physics, paving the way for technologies like radio, television, and all wireless communication.

His work also contributed significantly to thermodynamics and the kinetic theory of gases. Einstein kept a portrait of Maxwell in his study, alongside Newton and Faraday, stating that Maxwell's work was the 'most profound and most fruitful that physics has experienced since the time of Newton.'