Hertz, Heinrich Rudolf

Born Feb. 22, 1857, in Hamburg; died Jan 1, 1894, in Bonn. German physicist. One of the founders of electrodynamics.

Hertz studied at the Technische Hochschule in Dresden and at the universities of Munich and Berlin. In 1880 he became an assistant to H. von Helmholtz. From 1883 to 1885 he was a docent at the University of Kiel, and from 1885 to 1889 he was a professor at the Technische Hochschule in Karlsruhe. In 1889 he became a professor at the University of Bonn. His major works were in electrodynamics. Between 1886 and 1889, proceeding from Maxwell’s equations, Hertz experimentally proved the existence of electromagnetic waves and investigated their properties (reflection from mirrors, refraction in prisms, and so forth). Hertz generated electromagnetic waves with the help of an oscillator he invented (Hertz oscillator). He confirmed the conclusions of Maxwell’s theory that the speed of the propagation of electromagnetic waves in air is equal to the speed of light and established the identity of the principal properties of electromagnetic and light waves. Hertz also studied the propagation of electromagnetic waves in a conductor and pointed out the means of measuring the speed of their propagation. Expanding Maxwell’s theory, he gave a symmetrical form to the electrodynamic equations, which clearly revealed the correlation between electrical and magnetic phenomena. He developed electrodynamics of moving bodies, proceeding from the hypothesis that ether is dragged by moving bodies. However, experiments contradicted his theory of electrodynamics, and it was superseded by the electron theory of H. Lorentz. Hertz’ work in electrodynamics played an enormous role in the development of science and technology and was a basis for the development of wireless telegraphy, radio communication, television, and radar.

In 1886-87, Hertz observed and described for the first time the external photo-effect. He developed the theory of the resonant circuit, studied the properties of cathode rays, and investigated the effect of ultraviolet radiation on electrical discharges. In a series of articles on mechanics, Hertz formulated a theory of the collision of elastic spheres, calculated the collision time, and so forth. In his book Principles of Mechanics (1894), he summarized the general theorems of mechanics and its mathematical apparatus, proceeding from a unified principle (principle of least curvature). The unit of frequency of oscillation has been named after him.