Lorentz, Hendrick Antoon

Born July 18, 1853, in Arnhem; died Feb. 4, 1928, in Haarlem. Dutch physicis; founder of the electron theory.

Lorentz studied at the University of Leiden (1870-72) and was a professor there from 1878 to 1923. In 1923 he became director of research at the Teyler Institute in Haarlem.

In his doctoral dissertation (1875), Lorentz examined the reflection and refraction of light from the standpoint of J. Maxwell’s electromagnetic theory and showed that at the boundary between two media there arise four conditions (and not six, as required by the mechanical theory of light). This attested to the transverse character of light waves and served as proof of the electromagnetic theory of light. In 1878, Lorentz explained the dispersion of light in terms of the interference of incident waves and the secondary waves that arise with vibrations of charged particles under the influence of the incident waves. This work marked the first step toward the development of the electron theory, whose basic propositions Lorentz formulated in 1892. From the standpoint of the theory, any substance consists of discrete positive and negative charges whose motion and interaction are responsible for electromagnetic phenomena and for the electrical, magnetic, and optical properties of matter. Lorentz derived an expression for the force acting from an electromagnetic field on a moving charge.

Lorentz succeeded in explaining many phenomena by using the electron theory, such as the relation between the refractive index of a substance and its polarizability (the Lorentz-Lorenz formula), the relation between the coefficients of thermal and electrical conductivity in metals, and the Hall and Kerr effects. He explained the Zeeman effect and predicted the polarization of the components of the Zeeman splitting, for which he won a Nobel Prize in 1902 together with P. Zeeman. The classical electron theory found culmination in Lorentz’ monograph The Theory of Electrons (1909). The electron theory in the form in which Lorentz created it not only has fully retained its significance to the present day but has served as the basis for many modern physical concepts.

Lorentz was the author of classical works on the electrodynamics of moving media. In 1895 he formally introduced the concept of local time and showed that Maxwell’s equations are approximately valid in all uniformly and rectilinearly moving frames of references. To explain the Michelson-Morley experiment, Lorentz proceeded from the assumption that longitudinal dimensions contract in the direction of motion of bodies, which he (and independently of him the Irish physicist G. F. Fitzgerald) advanced in 1892. Lorentz introduced space-time transformations, which describe the transition from one inertial frame of reference system to another and leave Maxwell’s equations invariant (the Lorentz transformations, 1904), and also found the dependence of mass on velocity. These works by Lorentz foreshadowed the theory of relativity.

Lorentz is also the author of a number of works on thermodynamics and statistical physics (application of the virial theorem to the kinetic theory of gases, the thermodynamics of thermo-electric phenomena, the molecular theory of dilute solutions, the application of statistical methods to the electron theory of metals). Some of his works were devoted to the quantum theory of radiation and the general theory of relativity.

Lorentz was chairman of a planning committee for the partial reclamation of the Zuider Zee (1918-26), and for this project he worked out new mathematical methods of hydrodynamic calculations. He was the organizer and chairman of the Solway physics congresses (1911-27), a member of the League of Nations Committee of Intellectual Cooperation (from 1923, president from 1927), and a member of many of the world’s academies and scientific societies.