Lorentz, Hendrik Antoon

Lorentz, Hendrik Antoon (1853-1928), Dutch physicist and Nobel laureate. Lorentz was born in Arnhem and educated at the Leiden University, where he became professor of mathematical physics in 1878. He developed the electromagnetic theory of light and the electron theory of matter and formulated a consistent theory of electricity, magnetism, and light. With the Irish physicist George Francis FitzGerald, he formulated a theory on the change in shape of a body resulting from its motion; the effect, known as the Lorentz-FitzGerald contraction, was one of several important contributions that Lorentz made to the development of the theory of relativity. For his explanation of the phenomenon known as the Zeeman effect, Lorentz shared the 1902 Nobel Prize in physics with the Dutch physicist Pieter Zeeman.

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Lorentz, Hendrik Antoon

born July 18, 1853, Arnhem, Neth.

died Feb. 4, 1928, Haarlem

Dutch physicist and joint winner (with Pieter Zeeman) of the Nobel Prize for Physics in 1902 for his theory of electromagnetic radiation, which, confirmed by findings of Zeeman, gave rise to Albert Einstein's special theory of relativity.

In his doctoral thesis at the University of Leiden (1875), Lorentz refined the electromagnetic theory of James C. Maxwell of England so that it more satisfactorily explained thereflection and refraction of light. He was appointed professor of mathematical physics at Leiden in 1878. His work in physics was wide in scope, but his central aim was to construct a single theory to explain the relationship of electricity, magnetism, and light. Although, according to Maxwell's theory, electromagnetic radiation is produced by the oscillation of electric charges, the charges that produce light were unknown. Since it was generally believed that an electric current was made up of charged particles, Lorentz later theorized that the atoms of matter might also consist of charged particles and suggested that the oscillations of these charged particles (electrons) inside the atom were the source of light. If this were true, then a strong magnetic field ought to have an effect on the oscillations and therefore on the wavelength of the light thus produced. In 1896 Zeeman, a pupil of Lorentz, demonstrated this phenomenon, known as the Zeeman effect, and in 1902 they were awarded the Nobel Prize.

Lorentz' electron theory was not, however, successful in explaining the negative results of the Michelson-Morley experiment, an effort to measure the velocity of the Earth through the hypothetical luminiferous ether by comparing the velocities of light from different directions. In an attempt to overcome this difficulty he introduced in 1895 the idea of local time (different time rates in different locations). Lorentz arrived at the notionthat moving bodies approaching the velocity of light contract in the direction of motion. The Irish physicist George Francis FitzGerald had already arrived at this notion independently (see Lorentz-FitzGerald contraction, and in 1904 Lorentz extended his work and developed the Lorentz transformations. These mathematical formulas describe the increase of mass, shortening of length, and dilation of time that are characteristic of a moving body and form the basis of Einstein's special theory of relativity. In 1912 Lorentz became director of research at the Teyler Institute, Haarlem, though he remained honorary professor at Leiden, where he gave weekly lectures.