German physicist who first extended Joule's results to a general principle. He expressed the relationship between mechanics, heat, light, electricity, and magnetism by treating them all as manifestations of a single force. He presented a mathematical proof for his Law of Conservation of Force in Über die Erhaltung der Kraft (On the Conservation of Force, 1847). Helmholtz's use of the word "force" corresponds to what later became known as energy, so his law actually amounted to a statement of the Law of conservation of energy.

Helmholtz sought to synthesize Maxwell's electromagnetic theory of light with the central force theorem. To accomplish this, he formulated an electrodynamic theory of action at a distance in which electric and magnetic forces were propagated instantaneously. He attempted to demonstrate that body heat and muscular action of animals could be produced by the oxidation of foodstuffs.

Additional biographies: MacTutor (St. Andrews)