LORENTZ, HENDRIK ANTOON Dutch physicist, was born at Arnheim on July 18, 1853. He studied at Leyden, where he was appointed professor of mathematical physics in 1878. In 1923 he became director of research at the Teyler institute, Haarlem. He remained honorary professor at Leyden, where he gave a weekly lecture on modern physics, which was usually reported for publication by one of the audience. He died at Haarlem on Feb. 4, 1928.
Lorentz's work in physics was very wide in its scope, but its central aim, it appears, was to arrive at some consistent theory for electricity, magnetism and light. He tried to explain these phenomena by assuming an ether which was at rest and had electrons either at rest or moving in it. A number of phenomena were successfully explained on this electron theory, but it failed to give an explanation of the negative result of the Michelson Morley experiment. To overcome this difficulty Lorentz intro duced the idea of "local time" in 1895. The connection between this and the Fitzgerald contraction was pointed out by Larmor, and in 1903 Lorentz extended his work and arrived at the "Lorentz transformation," which formed the basis of the restricted theory of relativity. Lorentz's earlier investigations were originally pub lished in Dutch in the Archives Neerlandaises and consequently were not known to English physicists ; Lord Rayleigh and Sir Oliver Lodge were largely responsible for the spread of his ideas in England. His first paper, published in 1875, dealt with the re flection and refraction of light by dielectrics and metals. In 1880 he published a memoir on the relation between the refractive index and the density of a medium. This was the first application of Maxwell's theory to a medium consisting of discrete molecules. Lorentz dealt with optical dispersion and tried to give an ex planation on the assumption that it was due to resonant vibra tions. This work was continued in his two well known memoirs, La Theorie electromagnetique de Maxwell et son application aux corps mouvants (1892) and V ersuch einer Theorie der electrischen und optischen Erscheinungen in bewegten Korpern (1895). In
the latter memoir he deals with the electrodynamic field of a system moving with uniform velocity. Lorentz gave an explana tion of the Zeeman effect very soon after it was observed and pre dicted polarization effects which were verified later by experi ment. He was also the author of a number of papers on gravita tion theory, thermodynamics, radiation and kinetic theory.
Lorentz had a charming personality and kindly disposition. He spoke English, French and German fluently and he had the gift of clear exposition. He travelled and lectured extensively in Europe and America. He was a keen worker in the cause of international science and was chairman of the committee of in tellectual co-operation set up by the League of Nations. Lorentz was an honorary or corresponding member of most scientific societies and received many medals and other honours. In 1902 he was awarded, with Zeeman, the Nobel prize for physics. The jubilee of his doctorate was celebrated by a Festschrift to which physicists of all countries contributed. The Lorentz Foundation was established to promote the advancement of theoretical physics.
works include Abhandlungen 'fiber theo retische Physik (vol. i., 1907) ; this contains some of his collected papers with comments and additions of previously unpublished work; Theory of Electrons (i9o9); Differential and Integral Calculus (1882); Visible and Invisible Movements (19oI) ; The Einstein Theory of Relativity (1920) ; Clerk Maxwell's Electromagnetic Theory (1924). His lectures at Leyden university were published from igig onwards under his personal supervision with the title of Lessons on Theoretical Physics. (E. TR.)