Hendrik Lorentz ForMemRS
Lorentz in 1902
Born	18 July 1853 Arnhem, Netherlands
Died	4 February 1928 (aged 74) Haarlem, Netherlands
Alma mater	University of Leiden
Known for	show See list
Spouse	Aletta Catharina Kaiser ​ ​ (m. 1881)​
Children	3, including Geertruida
Awards	Nobel Prize in Physics (1902) ForMemRS (1905)[1] Rumford Medal (1908) Franklin Medal (1917) Copley Medal (1918)
Scientific career
Fields	Physics
Institutions	University of Leiden
Thesis	Over de theorie der terugkaatsing en breking van het licht (On the theory of reflection and refraction of light) (1875)
Doctoral advisor	Pieter Rijke
Doctoral students	Geertruida de Haas-Lorentz Adriaan Fokker Leonard Ornstein Hendrika Johanna van Leeuwen

Hendrik Antoon Lorentz ForMemRS (/ˈlɒrənts/; 18 July 1853 – 4 February 1928) was a Dutch physicist who shared the 1902 Nobel Prize in Physics with Pieter Zeeman for the 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 combined electric and magnetic forces acting on a charged particle in an electromagnetic field. Lorentz 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.

According to the biography published by the Nobel Foundation, "It may well be said that Lorentz was regarded by all theoretical physicists as the world's leading spirit, who completed what was left unfinished by his predecessors and prepared the ground for the fruitful reception of the new ideas based on the quantum theory."^[2] He received many other honours and distinctions, including a term as chairman of the International Committee on Intellectual Cooperation,^[3] the forerunner of UNESCO, between 1925 and 1928. He was the father and doctoral advisor of Geertruida de Haas-Lorentz.

Hendrik Lorentz was born in Arnhem, Gelderland, Netherlands, the son of Gerrit Frederik Lorentz (1822–1893), a well-off horticulturist, 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 in his local French church.^[4] From 1866 to 1869, he attended the "Hogere Burgerschool" in Arnhem, a new type of public high school recently established by Johan Rudolph 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.^[5]

Lorentz studied physics and mathematics at Leiden University, where he was strongly influenced by the teaching of astronomy professor Frederik Kaiser; it was his influence that led him to become a physicist. After earning a bachelor's degree, he returned to Arnhem in 1871 to teach night school classes in mathematics, but he continued his studies in Leiden in addition to his teaching position. In 1875, Lorentz earned a doctoral degree under Pieter Rijke on a thesis entitled "Over de theorie der terugkaatsing en breking van het licht" (On the theory of reflection and refraction of light), in which he refined the electromagnetic theory of James Clerk Maxwell.^[5][6]

On 17 November 1877, only 24 years of age, Lorentz was appointed to the newly established chair in theoretical physics at the University of Leiden. The position had initially been offered to Johan van der Waals, but he accepted a position at the Universiteit van Amsterdam.^[5] On 25 January 1878, Lorentz delivered his inaugural lecture on "De moleculaire theoriën in de natuurkunde" (The molecular theories in physics). In 1881, he became member of the Royal Netherlands Academy of Arts and Sciences.^[7]

During the first twenty years in 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. Lorentz 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.^[5]

Lorentz theorized that atoms might consist of charged particles and suggested that the oscillations of these charged particles were the source of light. When a colleague and former student of Lorentz's, Pieter Zeeman, discovered the Zeeman effect in 1896, Lorentz supplied its theoretical interpretation. The experimental and theoretical work was honored with the Nobel prize in physics in 1902. Lorentz' name is now associated with the Lorentz–Lorenz equation, the Lorentz force, the Lorentzian distribution, the Lorentz oscillator model and the Lorentz transformation.

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.^[8][9] 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 Lorentz 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^[10][11] (see Einstein synchronisation and Relativity of simultaneity). In 1892, with the attempt to explain the Michelson–Morley experiment, Lorentz also proposed that moving bodies contract in the direction of motion (see length contraction; George FitzGerald had already arrived at this conclusion in 1889).^[12]

In 1899 and again in 1904, Lorentz added time dilation to his transformations and published what Poincaré in 1905 named Lorentz transformations.^[13][14]

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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.^[15] 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.