Editing Hendrik Lorentz (section)

===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=}}