The work of the physicist Hendrik Antoon Lorentz (1853-1928) on electromagnetic theory led to notions equivalent to some basic postulates of the special theory of relativity.

Hendrik Antoon Lorentz, the son of Gerrit Frederik Lorentz and his wife, Geertruida van Ginkel, was born on July 18, 1853, in Aarnhem. At the age of 9 he mastered the use of a table of logarithms. In high school he excelled in the sciences, as well as in history and languages. In 1870 he passed the examinations to qualify for the University of Leiden. By the end of the next year he had become a doctoral candidate.

During the next 2 years Lorentz taught high school physics and mathematics in Aarnhem. In June 1873 he returned to Leiden and received his doctoral degree; his dissertation revealed at one stroke his extraordinary grasp of what constituted at that time the most advanced and most portentous part of theoretical physics, J. C. Maxwell's electromagnetic theory. Lorentz was not only among the relatively few on the Continent who at that time were thoroughly familiar with Maxwell's theory, but his dissertation carried some of Maxwell's ideas considerably further.

By a fortunate coincidence, Dutch university education was expanded in 1877. At the University of Leiden a new chair in physics was set up for theoretical physics with the 24-year-old Lorentz as its first occupant. The next 20 years in Lorentz's life were a time of quiet, almost isolated study. He kept abreast of the latest publications in physics without, however, trying to make personal contacts with physicists abroad. When one day he was told about a foreign-looking man wandering about on Leiden's main street, his spontaneous reaction was: "I hope he will not turn out to be a physicist." He did not in fact make his first international contact until 1897. By then he had become the father of two daughters and a son, following his marriage in 1881 to Aletta Kaiser, the niece of his physics professor at Leiden, P. Kaiser.

After his appearance at the Congress of German Scientists and Physicians in Düsseldorf in 1897, Lorentz became a central figure of international gatherings of physicists. This was due only in part to the charm of his personality and to his ability to speak in a highly literary style in German, English, and French. The 20 years spent in the privacy of his study where, as his children put it, he walked up and down like a polar bear, had been rich in creative results. First came his highly successful textbooks in calculus and physics, the latter of which went through nine editions. Far more important was the gradual development of his electromagnetic theory, in which electromagnetism was based strictly on the existence of electrons that acted on each other through a stationary ether. His assumptions led directly to the interrelation between the frequency of the field and the value of the refractive index.

These researches led Lorentz to the question of electrical and optical phenomena in moving bodies, a crucial issue in electromagnetic theory. As is well known, the uniform motion of bodies leaves those phenomena unchanged. In 1895 Lorentz put forward the now famous transformation equations that explain this situation, or rather leave the fundamental equations of electromagnetism in the same form in all reference systems moving with uniform velocity with respect to one another. In 1903 Lorentz derived the principle that electromagnetic and optical phenomena are independent of the velocity of the system in which they take place, as long as the velocity is smaller than the velocity of light. The principle is known as Lorentz's principle of correlation, and its content is equivalent to that of the special theory of relativity spelled out by Albert Einstein with more incisive generality in 1905.

The most spectacular success of Lorentz's electromagnetic theory was not its anticipation of some of Einstein's great insights, but rather the explanation of the splitting of spectral lines in strong magnetic fields, first observed by Pieter Zeeman in 1896. The discovery and the explanation made Zeeman and Lorentz the joint recipients in 1902 of the Nobel Prize for physics. Lorentz's electron theory received a full-fledged treatment in 1906 in his lectures at Columbia University, published under the title The Theory of Electrons. This first visit to the United States was followed by three more after World War I, to the California Institute of Technology and to Mt. Wilson Observatory.

After the war Lorentz was president of the famous Solvay Conferences for physics, a telling evidence of his stature in a generation that produced a galaxy of geniuses in physics. In his own country he served as director of the very complex studies preliminary to the closing of the Zuiderzee. Although in 1912 Lorentz became curator of the laboratory of the Teyler Stichting (Institute) in Haarlem, he continued at Leiden his Monday morning lectures, which were often attended by leading physicists from abroad. He died after a short illness on Feb. 4, 1928.

Further Reading

• Excellent insights into personal, scientific, and civic aspects of Lorentz's life are given in the collection of essays edited by his daughter, Geertruida Luberta De Haas-Lorentz, H. A. Lorentz: Impressions on His Life and Work (trans. 1957). For an authoritative discussion of Lorentz's role in the development of modern physics consult E. T. Whittaker, A History of the Theories of Aether and Electricity (1910; rev. ed., 2 vols., 1951-1953).