Editing Hendrik Lorentz (section)

==Career==

===Professor in Leiden===
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 [[Johannes Diderik van der Waals|Johan van der Waals]], but he accepted a position at the [[Universiteit van Amsterdam]].<ref name="NtvN2011"/> On 25 January 1878, Lorentz delivered his inaugural lecture on ''"{{lang|nl|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]].<ref>{{cite web|url=http://www.dwc.knaw.nl/biografie/pmknaw/?pagetype=authorDetail&aId=PE00001670 |title=Hendrik Antoon Lorentz (1853–1928) |publisher=Royal Netherlands Academy of Arts and Sciences |access-date=17 July 2015}}</ref>

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.<ref name="NtvN2011"/>

Lorentz theorized that [[atom]]s 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]].

===Electrodynamics and relativity===
{{Main|Lorentz ether theory|History of special relativity|History of Lorentz transformations#Lorentz1|History of Lorentz transformations#Lorentz2}}

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]].<ref>{{Citation
|author=Lorentz, Hendrik Antoon
|year=1892
|title=La Théorie electromagnétique de Maxwell et son application aux corps mouvants
|url = https://archive.org/details/lathorielectrom00loregoog
|journal=Archives Néerlandaises des Sciences Exactes et Naturelles
|volume=25
|pages=363–552}}</ref><ref>{{Citation
|author=Lorentz, Hendrik Antoon
|year=1895
|title=Versuch einer Theorie der electrischen und optischen Erscheinungen in bewegten Körpern
|location=Leiden
|publisher=E.J. Brill|title-link=s:de:Versuch einer Theorie der electrischen und optischen Erscheinungen in bewegten Körpern
}}
*English Wikisource translation: [[s:Translation:Attempt of a Theory of Electrical and Optical Phenomena in Moving Bodies|Attempt of a Theory of Electrical and Optical Phenomena in Moving Bodies]]</ref> 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<ref>{{Citation
|author=Poincaré, Henri
|year=1900
|title=La théorie de Lorentz et le principe de réaction
|journal=Archives Néerlandaises des Sciences Exactes et Naturelles
|volume=5
|pages=252–278|title-link=s:fr:La théorie de Lorentz et le principe de réaction
}}. See also the [http://www.physicsinsights.org/poincare-1900.pdf English translation].</ref><ref>{{Citation
|author=Poincaré, Henri
|year=1904
|chapter=[[s:The Principles of Mathematical Physics|The Principles of Mathematical Physics]]
|title=Congress of arts and science, universal exposition, St. Louis, 1904
|volume=1
|pages=604–622
|publisher=Houghton, Mifflin and Company
|location=Boston and New York}}</ref> (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 Francis FitzGerald|George FitzGerald]] had already arrived at this conclusion in 1889).<ref>{{Citation
|last=Lorentz
|first=Hendrik Antoon
|year=1892b
|title=The Relative Motion of the Earth and the Aether
|journal=Zittingsverlag Akad. V. Wet.
|pages=74–79
|volume=1|title-link=s:Translation:The Relative Motion of the Earth and the Aether
}}</ref>

In 1899 and again in 1904, Lorentz added [[time dilation]] to his transformations and published what Poincaré in 1905 named [[Lorentz transformations]].<ref>{{Citation
|author=Lorentz, Hendrik Antoon
|year=1899
|title=Simplified Theory of Electrical and Optical Phenomena in Moving Systems
|journal=Proceedings of the Royal Netherlands Academy of Arts and Sciences
|volume=1
|pages=427–442|title-link=s:Simplified Theory of Electrical and Optical Phenomena in Moving Systems
|bibcode=1898KNAB....1..427L
}}</ref><ref>{{Citation
|author=Lorentz, Hendrik Antoon
|year=1904
|title=Electromagnetic phenomena in a system moving with any velocity smaller than that of light
|journal=Proceedings of the Royal Netherlands Academy of Arts and Sciences
|volume=6
|pages=809–831|title-link=s:Electromagnetic phenomena
|bibcode=1903KNAB....6..809L
}}</ref>{{electromagnetism|Scientists}}
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.<ref name=Macrossan/> 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 and special relativity===
[[File:Einstein en Lorentz.jpg|thumb|[[Albert Einstein]] and Hendrik Antoon Lorentz, photographed by [[Paul Ehrenfest|Ehrenfest]] in front of his home in Leiden in 1921]][[File:League of Nations Commission 067.tif|thumb|Lorentz (left) at the [[International Committee on Intellectual Cooperation]] of the [[League of Nations]], here with [[Albert Einstein]]]]

[[File:Hendrik Antoon Lorentz - Lessen over theoretische natuurkunde - I. Stralingstheorie (1910-1911) - Titelpagina, 1919.jpg|thumb|His published university lectures in theoretical physics. Part 1. ''Stralingstheorie'' (1910-1911, ''Radiation theory'') in Dutch, edited by his student [[Adriaan Fokker|A. D. Fokker]], 1919.]]

In 1905, Einstein would use many of the concepts, mathematical tools and results Lorentz discussed to write his paper entitled "[[Annus Mirabilis Papers#Special relativity|On the Electrodynamics of Moving Bodies]]",<ref>{{Citation
|author=Einstein, Albert
|year=1905
|title=Zur Elektrodynamik bewegter Körper
|journal=Annalen der Physik
|volume=322
|issue=10
|pages=891–921
|url=http://www.physik.uni-augsburg.de/annalen/history/einstein-papers/1905_17_891-921.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://www.physik.uni-augsburg.de/annalen/history/einstein-papers/1905_17_891-921.pdf |archive-date=2022-10-09 |url-status=live
|doi=10.1002/andp.19053221004|bibcode = 1905AnP...322..891E |doi-access=free
}}. See also: [http://www.fourmilab.ch/etexts/einstein/specrel/ English translation].</ref> known today as the special theory of relativity. Because Lorentz laid the fundamentals for the work by Einstein, this theory was originally called the ''Lorentz–Einstein theory''.<ref>{{Cite book|author=Miller, Arthur I.|year=1981|title=Albert Einstein's special theory of relativity. Emergence (1905) and early interpretation (1905–1911)|location=Reading|publisher=Addison–Wesley|isbn=978-0-201-04679-3|url-access=registration|url=https://archive.org/details/alberteinsteinss0000mill}}</ref>

In 1906, Lorentz's electron theory received a full-fledged treatment in [[Ernest Kempton Adams Lectures|his lectures]] at [[Columbia University]], published under the title The Theory of Electrons.

The increase of mass was the first prediction of Lorentz and Einstein to be tested, but some experiments by [[Walter Kaufmann (physicist)|Kaufmann]] appeared to show a slightly different mass increase; this led Lorentz to the famous remark that he was "au bout de mon latin" ("at the end of my [knowledge of] Latin" = at his wit's end)<ref>{{cite web|url=http://www.univ-nancy2.fr/poincare/chp/text/lorentz1.html |title=Lorentz à Poincaré |access-date=31 March 2017 |url-status=dead |archive-url=https://web.archive.org/web/20050221211608/http://www.univ-nancy2.fr/poincare/chp/text/lorentz1.html |archive-date=21 February 2005 }}</ref>  The confirmation of his prediction had to wait until 1908 and later (see [[Kaufmann–Bucherer–Neumann experiments]]).

Lorentz published a series of papers dealing with what he called "Einstein's principle of relativity". For instance, in 1909,<ref name=lor09>{{citation |first = Hendrik Antoon |last = Lorentz |title = The theory of electrons and its applications to the phenomena of light and radiant heat; a course of lectures delivered in Columbia University, New York, in March and April 1906 |place = New York|publisher = Columbia University Press |year = 1916 | url= https://archive.org/details/electronstheory00lorerich}}</ref>{{failed verification|date=March 2018}} 1910,<ref name=lor10>{{Cite book|author=Lorentz, Hendrik Antoon
|year=1910|orig-year=1913|chapter=[[s:Das Relativitätsprinzip und seine Anwendung|Das Relativitätsprinzip und seine Anwendung auf einige besondere physikalische Erscheinungen]]|title=Das Relativitätsprinzip. Eine Sammlung von Abhandlungen|editor=Blumenthal, Otto |editor2=Sommerfeld, Arnold|pages=74–89}}
*English Wikisource translation: [[s:Translation:The Principle of Relativity and its Application to some Special Physical Phenomena|The Principle of Relativity and its Application to some Special Physical Phenomena]]</ref><ref>{{Citation
|author=Lorentz, Hendrik Antoon
|year=1931|orig-year=1910
|title=Lectures on theoretical physics, Vol. 3
|publisher=MacMillan
|location=London}}</ref> 1914.<ref>{{Cite book
|author=Lorentz, Hendrik Antoon|year=1914|title=Das Relativitätsprinzip. Drei Vorlesungen gehalten in Teylers Stiftung zu Haarlem (1913)|publisher=B.G. Teubner
|location=Leipzig and Berlin|title-link=s:de:Das Relativitätsprinzip (Lorentz)}}</ref> In his 1906 lectures published with additions in 1909 in the book "The theory of electrons" (updated in 1915), he spoke affirmatively of Einstein's theory:<ref name=lor09 />

{{Blockquote|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.|author=|title=|source=}}

Though Lorentz still maintained that there is an (undetectable) aether in which resting clocks indicate the "true time":

{{Blockquote|1909: Yet, I think, something may also be claimed in favour of the form in which I have presented the theory. I cannot but regard the ether, which can be the seat of an electromagnetic field with its energy and its vibrations, as endowed with a certain degree of substantiality, however different it may be from all ordinary matter.<ref name=lor09 /><br /> 1910: Provided that there is an aether, then under all systems x, y, z, t, one is preferred by the fact, that the coordinate axes as well as the clocks are resting in the aether. If one connects with this the idea (which I would abandon only reluctantly) that space and time are completely different things, and that there is a "true time" (simultaneity thus would be independent of the location, in agreement with the circumstance that we can have the idea of infinitely great velocities), then it can be easily seen that this true time should be indicated by clocks at rest in the aether. However, if the relativity principle had general validity in nature, one wouldn't be in the position to determine, whether the reference system just used is the preferred one. Then one comes to the same results, as if one (following Einstein and Minkowski) deny the existence of the aether and of true time, and to see all reference systems as equally valid. Which of these two ways of thinking one is following, can surely be left to the individual.<ref name=lor10 />}}

Lorentz also gave credit to Poincaré's contributions to relativity.<ref>{{Citation
|author=Lorentz, Hendrik Antoon
|year=1921|orig-year=1914
|title=Deux Mémoires de Henri Poincaré sur la Physique Mathématique
|journal=Acta Mathematica
|volume=38
|issue=1
|pages=293–308
|doi=10.1007/BF02392073|title-link=s:fr:Deux Mémoires de Henri Poincaré sur la Physique Mathématique|doi-access=free
}}
*English Wikisource translation: [[s:Translation:Two Papers of Henri Poincaré on Mathematical Physics|Two Papers of Henri Poincaré on Mathematical Physics]]</ref>

{{Blockquote|Indeed, for some of the physical quantities which enter the formulas, I did not indicate the transformation which suits best. That was done by Poincaré and then by Mr. Einstein and Minkowski. I did not succeed in obtaining the exact invariance of the equations. Poincaré, on the contrary, obtained a perfect invariance of the equations of electrodynamics, and he formulated the "postulate of relativity", terms which he was the first to employ. Let us add that by correcting the imperfections of my work he never reproached me for them.|author=|title=|source=}}

===Lorentz and general relativity===
Lorentz was one of few scientists who supported Einstein's search for [[general relativity]] from the beginning – he wrote several research papers and discussed with Einstein personally and by letter.<ref>{{Cite journal|author=Kox, A.J.|year=1993|title= Einstein, Lorentz, Leiden and general relativity|journal=Class. Quantum Grav.|volume=10|pages=S187–S191|doi= 10.1088/0264-9381/10/S/020|bibcode = 1993CQGra..10S.187K |s2cid=250884975 }}</ref> For instance, he attempted to combine Einstein's formalism with [[Hamilton's principle]] (1915),<ref>{{Citation
|author=Lorentz, Hendrik Antoon
|year=1915
|title=On Hamilton's principle in Einstein's theory of gravitation
|journal=Proceedings of the Royal Netherlands Academy of Arts and Sciences
|volume=19
|pages=751–765|title-link=s:On Hamilton's principle in Einstein's theory of gravitation
|bibcode=1917KNAB...19..751L
}}</ref>
and to reformulate it in a [[coordinate-free]] way (1916).<ref>{{Citation
|author=Lorentz, Hendrik Antoon
|year=1916
|title=On Einstein's Theory of gravitation I–IV
|journal=Proceedings of the Royal Netherlands Academy of Arts and Sciences
|volume=19/20
|pages=1341–1361, 2–34|title-link=s:On Einstein's Theory of gravitation
}}</ref><ref>{{Cite book|author=Janssen, M.|year=1992|chapter=H. A. Lorentz's Attempt to Give a Coordinate-free Formulation of the General. Theory of Relativity.|title=Studies in the History of General Relativity|publisher=Birkhäuser|location=Boston|isbn=978-0817634797|pages=344–363}}</ref> Lorentz wrote in 1919:<ref>{{citation | first=Hendrik Antoon | last=Lorentz | title=The Einstein Theory of Relativity | location=New York | publisher=Bentano's | year=1920| title-link=s:The Einstein Theory of Relativity }}</ref>

{{Blockquote|The total eclipse of the sun of May 29, resulted in a striking confirmation of the new theory of the universal attractive power of gravitation developed by Albert Einstein, and thus reinforced the conviction that the defining of this theory is one of the most important steps ever taken in the domain of natural science.}}

===Lorentz and quantum mechanics===

Lorentz gave a series of lectures in the fall of 1926 at [[Cornell University]] on the new [[quantum mechanics]]; in these he presented [[Erwin Schrödinger]]'s [[Schrödinger equation|wave mechanics]].<ref>{{cite book|last1=Lorentz|first1=H. A.|title=The New Quantum Theory|date=1926|publisher=Typescript of Lecture Notes|location=Ithaca, NY |url=http://labs.plantbio.cornell.edu/wayne/pdfs/TheQuantumTheory.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://labs.plantbio.cornell.edu/wayne/pdfs/TheQuantumTheory.pdf |archive-date=2022-10-09 |url-status=live|access-date=12 August 2016}}</ref>

===Change of priorities===
In 1910, Lorentz decided to reorganize his life. His teaching and management duties at Leiden University were taking up too much of his time, leaving him little time for research. In 1912, he resigned from his chair of theoretical physics to become curator of the "Physics Cabinet" at [[Teylers Museum]] in [[Haarlem]]. He remained connected to Leiden University as an external professor, and his "Monday morning lectures" on new developments in theoretical physics soon became legendary.<ref name="NtvN2011"/>

Lorentz initially asked Einstein to succeed him as professor of theoretical physics at Leiden. However, Einstein could not accept because he had just accepted a position at [[ETH Zurich]]. Einstein had no regrets in this matter, since the prospect of having to fill Lorentz's shoes made him shiver. Instead Lorentz appointed [[Paul Ehrenfest]] as his successor in the chair of theoretical  physics at the Leiden University, who would found the Institute for Theoretical Physics which would become known as the [[Lorentz Institute]].<ref name="NtvN2011"/>

===Civil work===
After World War I, Lorentz was one of the driving forces behind the founding of the "Wetenschappelijke Commissie van Advies en Onderzoek in het Belang van Volkswelvaart en Weerbaarheid", a committee which was to harness the scientific potential united in the [[Royal Netherlands Academy of Arts and Sciences]] (KNAW) for solving civil problems such as food shortage which had resulted from the war. Lorentz was appointed chair of the committee. However, despite the best efforts of many of the participants the committee would harvest little success. The only exception being that it ultimately resulted in the founding of TNO, the [[Netherlands Organisation for Applied Scientific Research]].<ref name="NtvN2011"/>

Lorentz was also asked by the Dutch government to chair a committee to calculate some of the effects of the proposed [[Afsluitdijk]] (Enclosure Dam) flood control dam on water levels in the {{lang|nl|[[Waddenzee]]|italic=no}}. [[Hydraulic engineering]] was mainly an empirical science at that time, but the disturbance of the tidal flow caused by the Afsluitdijk was so unprecedented that the empirical rules could not be trusted. Originally Lorentz was only supposed to have a coordinating role in the committee, but it quickly became apparent that Lorentz was the only physicist to have any fundamental traction on the problem. In the period 1918 till 1926, Lorentz invested a large portion of his time in the problem.<ref>{{Cite web|url=https://www.radionetherlandsarchives.org/lorentz-the-grand-old-man-of-physics/|title=Lorentz: the Grand Old Man of Physics|work=Radio Netherlands Archives |date=13 March 2000}}</ref> Lorentz proposed to start from the basic [[hydrodynamic]] equations of motion and solve the problem numerically. This was feasible for a "[[human computer]]", because of the quasi-one-dimensional nature of the water flow in the {{lang|nl|Waddenzee|italic=no}}. The Afsluitdijk was completed in 1932, and the predictions of Lorentz and his committee turned out to be remarkably accurate.<ref >{{cite web|url=http://ilorentz.org/history/zuiderzee/zuiderzee.html |title=Carlo Beenakker |publisher=Ilorentz.org |access-date=1 February 2012}}</ref><ref name="NtvN2011"/> One of the two sets of locks in the Afsluitdijk was named after him.