Hendrik Antoon Lorentz (18 July 1853 – 4 February 1928) was a Dutch theoretical physicist who shared the 1902 Nobel Prize in Physics with Pieter Zeeman for their discovery and theoretical explanation of the Zeeman effect. He derived the Lorentz transformation of the special theory of relativity, as well as the Lorentz force, which describes the force acting on a charged particle in an electromagnetic field. He was also responsible for the Lorentz oscillator model, a classical model used to describe the anomalous dispersion observed in dielectric materials when the driving frequency of the electric field was near the resonant frequency of the material, resulting in abnormal refractive indices.
Lorentz received many other honors and distinctions, including a term as Chairman of the International Committee on Intellectual Cooperation, the forerunner of UNESCO, from 1925 until his death in 1928.
Hendrik Antoon Lorentz was born on 18 July 1853 in Arnhem, Netherlands, the son of Gerrit Frederik Lorentz (1822–1893) and Geertruida van Ginkel (1826–1861). In 1862, after his mother's death, his father married Luberta Hupkes. Despite being raised as a Protestant, he was a freethinker in religious matters and regularly attended Catholic mass at his local French church.
From 1866 to 1869, Lorentz attended the Hogere Burgerschool in Arnhem, a new type of public high school recently established by Johan Thorbecke. His results in school were exemplary; not only did he excel in the physical sciences and mathematics, but also in English, French, and German. In 1870, he passed the exams in classical languages, which were then required for admission to university.
In 1870, Lorentz entered Leiden University, where he was strongly influenced by the teaching of astronomy professor Frederik Kaiser; it was his influence that led Lorentz to become a physicist. The following year, he obtained a B.Sc. in Mathematics and Physics. In 1872, he returned to Arnhem to become a night school teacher, while also continuing his studies at Leiden. In 1875, he received his Ph.D. under Pieter Rijke with a thesis on the reflection and refraction of light, in which he refined the electromagnetic theory of James Clerk Maxwell.
In 1878, Lorentz was appointed to the newly established Chair of Theoretical Physics at Leiden University; the position had initially been offered to Johannes van der Waals, but he had just accepted a professorship at the University of Amsterdam. On 25 January 1878, he delivered his inaugural lecture titled De moleculaire theoriën in de natuurkunde (The molecular theories in physics).
During his first 20 years at Leiden, Lorentz was primarily interested in the electromagnetic theory of electricity, magnetism, and light. After that, he extended his research to a much wider area while still focusing on theoretical physics. He made significant contributions to fields ranging from hydrodynamics to general relativity. His most important contributions were in the area of electromagnetism, the electron theory, and relativity.
In 1910, Lorentz decided to reorganize his career; his teaching and management duties at Leiden University were taking up too much of his time, leaving him little time for research. He initially asked Albert Einstein to succeed him as Professor of Theoretical Physics at Leiden. However, Einstein did not accept, because he had just taken up a position at ETH Zurich and the prospect of having to fill Lorentz's shoes made him shiver. He ultimately chose Paul Ehrenfest as his successor.
In 1912, Lorentz resigned from his chair at Leiden University to become Curator of the Physical Cabinet at Teylers Museum in Haarlem. He continued to teach at Leiden as Extraordinary Professor, delivering his famous "Monday morning lectures" on new developments in theoretical physics.
Electrodynamics and relativity
In 1892 and 1895, Lorentz worked on describing electromagnetic phenomena (the propagation of light) in reference frames that move relative to the postulated luminiferous aether. He discovered that the transition from one to another reference frame could be simplified by using a new time variable that he called local time and which depended on universal time and the location under consideration. Although he did not give a detailed interpretation of the physical significance of local time, with it, he could explain the aberration of light and the result of the Fizeau experiment. In 1900 and 1904, Henri Poincaré called local time Lorentz's "most ingenious idea" and illustrated it by showing that clocks in moving frames are synchronized by exchanging light signals that are assumed to travel at the same speed against and with the motion of the frame (see Einstein synchronisation and Relativity of simultaneity). In 1892, with the attempt to explain the Michelson–Morley experiment, he also proposed that moving bodies contract in the direction of motion.
In 1899 and again in 1904, Lorentz added time dilation to his transformations and published what Poincaré in 1905 named Lorentz transformations.
It was apparently unknown to Lorentz that Joseph Larmor had used identical transformations to describe orbiting electrons in 1897. Larmor's and Lorentz's equations look somewhat dissimilar, but they are algebraically equivalent to those presented by Poincaré and Einstein in 1905. Lorentz's 1904 paper includes the covariant formulation of electrodynamics, in which electrodynamic phenomena in different reference frames are described by identical equations with well defined transformation properties. The paper clearly recognizes the significance of this formulation, namely that the outcomes of electrodynamic experiments do not depend on the relative motion of the reference frame. The 1904 paper includes a detailed discussion of the increase of the inertial mass of rapidly moving objects in a useless attempt to make momentum look exactly like Newtonian momentum; it was also an attempt to explain the length contraction as the accumulation of "stuff" onto mass making it slow and contract.
Lorentz theorized that atoms consist of charged particles, and suggested that the oscillations of these charged particles were the source of light. His colleague and former student, Pieter Zeeman, discovered the Zeeman effect in 1896, and Lorentz supplied its theoretical interpretation. Their joint work earned them the Nobel Prize in Physics in 1902.
In 1905, Einstein would use many of the concepts, mathematical tools and results Lorentz discussed to write his paper titled Zur Elektrodynamik bewegter Körper (On the electrodynamics of moving bodies), known today as the special theory of relativity. Einstein's unique perspective on the topic was not widely understood initially, causing some physicists to confusingly refer to the theory as the Lorentz–Einstein theory.
In 1910, Lorentz's 1906 lectures at Columbia University, were published under the title The Theory of Electrons. Lorentz covered his entire theory of the electron, including his work and that of Einstein on relativity. In this work he spoke affirmatively of Einstein's theory:
It will be clear by what has been said that the impressions received by the two observers A0 and A would be alike in all respects. It would be impossible to decide which of them moves or stands still with respect to the ether, and there would be no reason for preferring the times and lengths measured by the one to those determined by the other, nor for saying that either of them is in possession of the "true" times or the "true" lengths. This is a point which Einstein has laid particular stress on, in a theory in which he starts from what he calls the principle of relativity, I cannot speak here of the many highly interesting applications which Einstein has made of this principle. His results concerning electromagnetic and optical phenomena agree in the main with those which we have obtained in the preceding pages, the chief difference being that Einstein simply postulates what we have deduced, with some difficulty and not altogether satisfactorily, from the fundamental equations of the electromagnetic field. By doing so, he may certainly take credit for making us see in the negative result of experiments like those of Michelson, Rayleigh and Brace, not a fortuitous compensation of opposing effects, but the manifestation of a general and fundamental principle. It would be unjust not to add that, besides the fascinating boldness of its starting point, Einstein's theory has another marked advantage over mine. Whereas I have not been able to obtain for the equations referred to moving axes exactly the same form as for those which apply to a stationary system, Einstein has accomplished this by means of a system of new variables slightly different from those which I have introduced.