Editing Woldemar Voigt

{{Short description|German physicist (1850–1919)}}
{{about||the German aerospace engineer|Woldemar Voigt (engineer)}}
{{Use dmy dates|date=October 2019}}
{{Infobox scientist
| honorific_suffix  = {{post-nominals|country=GBR|size=100%|ForMemRS}}
| name              = Woldemar Voigt
| image             = Woldemar Voigt, c. 1908.jpg
| image_size        = 
| caption           = Voigt, {{circa|1908}}
| birth_date        = {{birth date|1850|9|2|df=y}}
| birth_place       = [[Leipzig]], [[Kingdom of Saxony]], [[German Confederation]]
| death_date        = {{death date and age|1919|12|13|1850|9|2|df=y}}
| death_place       = [[Göttingen]], [[Free State of Prussia]], [[Weimar Republic]]
| alma_mater        = [[University of Königsberg]]
| known_for         = {{ubl|[[Voigt effect]]|[[Rule of mixtures#Voigt Modulus|Voight modulus]]|[[Voigt notation]]|[[Voigt profile]]|[[History of Lorentz transformations#Voigt (1887)|Voigt transformation]]|[[Voigt-Thomson law|Voigt–Thomson law]]|[[Kelvin–Voigt material]]|[[Dyakonov–Voigt wave]]|[[Piezoelectricity]]|[[Pyroelectricity]]}}
| prizes            = [[Fellow of the Royal Society#Foreign member|ForMemRS]] (1913)
| field             = [[Physics]]
| work_institution  = [[University of Göttingen]]
| doctoral_advisor  = [[Franz Ernst Neumann]]
| doctoral_students = [[Paul Drude]]
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| religion          =
| footnotes         =  
}}

'''Woldemar Voigt''' ({{IPA|de|ˈvɔldemaʁ foːkt|lang|de-Voigt2.ogg}}; 2 September 1850 – 13 December 1919) was a German [[physicist]].

==Biography==
Voigt was born in [[Leipzig]], and died in [[Göttingen]]. He was a student of [[Franz Ernst Neumann]].<ref name="olesko" />
Voigt taught at the [[Georg August University of Göttingen]] and eventually went on to head the Mathematical Physics Department there. He was succeeded in 1914 by [[Peter Debye]], who took charge of the theoretical department of the Physical Institute.

Voigt worked on [[crystal]] [[physics]], [[thermodynamics]] and [[electro-optics]]. His main work was the ''Lehrbuch der Kristallphysik'' (''Textbook on crystal physics''), first published in 1910. He discovered what is now called the [[Voigt effect]] in 1898. The word [[tensor]] in its current meaning was introduced by him in 1898.<ref name="crystals" /> [[Voigt profile]] and [[Voigt notation]] are named after him. He was also an amateur musician and became known as a Bach expert (see External links). He was the first to suggest, in 1886, that Bach's [[Concerto for two harpsichords in C minor, BWV 1060]] was originally scored for violin and oboe.

In 1887 Voigt formulated a form of the [[Lorentz transformation]] between a rest frame of reference and a frame moving with speed <math>v</math> in the <math>x</math> direction. However, as Voigt himself said, the transformation was aimed at a specific problem and did not carry with it the idea of a general [[Coordinate system#Transformations|coordinate transformation]], as is the case in [[relativity theory]].<ref name="doppler" />

==Voigt transformation==
{{Further|History of Lorentz transformations}}
In modern notation Voigt's transformation was
:<math>x' = x - vt,</math>
:<math>y' = y/\gamma,</math>
:<math>z' = z/\gamma,</math>
:<math>t' = t - vx/c^2,</math>
where <math>\gamma = 1/\sqrt{1 - v^2/c^2}</math>.
If the right-hand sides of his equations are multiplied by <math>\gamma</math>, they become the modern [[Lorentz transformation]]. [[Hermann Minkowski]] said in 1908 that the transformations which play the main role in the principle of relativity were first examined by Voigt in 1887. Also [[Hendrik Lorentz]] (1909) is on record as saying that he could have taken these transformations into his theory of electrodynamics, if only he had known of them, rather than developing his own. It is interesting then to examine the consequences of these transformations from this point of view. Lorentz might then have seen that the transformation introduced [[relativity of simultaneity]], and also [[time dilation]]. However, the magnitude of the dilation was greater than the now accepted value in the Lorentz transformations. Moving clocks, obeying Voigt's time transformation, indicate an elapsed time
<math>\Delta t_\text{Voigt} = \gamma^{-2} \Delta t = \gamma^{-1} \Delta t_\text{Lorentz}</math>, while stationary clocks indicate an elapsed time <math>\Delta t</math>.

Since Voigt's transformation preserves the speed of light in all frames, the [[Michelson–Morley experiment]] and the [[Kennedy–Thorndike experiment]] can not distinguish between the two transformations. The crucial question is the issue of time dilation. The experimental measurement of [[time dilation]] by [[Ives–Stilwell experiment|Ives and Stillwell]] (1938) and others settled the issue in favor of the Lorentz transformation.

==See also==
*[[German inventors and discoverers]]
*[[Physical crystallography before X-rays]]

==References==
{{Wikisource|Translation:On the Principle of Doppler|On the Principle of Doppler}}
;Primary Sources
{{reflist|refs=
<ref name="olesko">{{Citation | author=Olesko, Kahryn M. | year=1991| title=Physics as a Calling: Discipline and Practice in the Königsberg Seminar for Physics | publisher=Cornell University Press}}</ref>
<ref name="crystals">Woldemar Voigt, ''Die fundamentalen physikalischen Eigenschaften der Krystalle in elementarer Darstellung'' [The fundamental physical properties of crystals in an elementary presentation] (Leipzig, Germany: Veit & Co., 1898), p. 20. [https://books.google.com/books?id=QhBDAAAAIAAJ&q=tensortripel&pg=PA20 From page 20:] ''"Wir wollen uns deshalb nur darauf stützen, dass Zustände der geschilderten Art bei Spannungen und Dehnungen nicht starrer Körper auftreten, und sie deshalb tensorielle, die für sie charakteristischen physikalischen Grössen aber Tensoren nennen."'' (We therefore want [our presentation] to be based only on [the assumption that] conditions of the type described occur during stresses and strains of non-rigid bodies, and therefore call them "tensorial" but call the characteristic physical quantities for them "tensors".)</ref>
<ref name="doppler">{{Citation | author=Voigt, W. | year=1887 | journal=Göttinger Nachrichten | title= Ueber das Doppler'sche Princip (On the Principle of Doppler) |pages= 41–51 |issue=7}}; Reprinted with additional comments by Voigt in ''Physikalische Zeitschrift'' '''XVI''', 381–386 (1915).</ref>
}}
*{{Citation | author=Voigt, W. | year=1887 | journal=Göttinger Nachrichten | title= Theorie des Lichts für bewegte Medien  | url= http://gdz.sub.uni-goettingen.de/no_cache/dms/load/img/?IDDOC=55436 |pages= 177–238 |issue=8 }}; This article ends with the announcement that in a forthcoming article the principles worked out so far shall be applied to the problems of reflection and refraction. The article contains on p.&nbsp;235, last paragraph, and on p.&nbsp;236, 2nd paragraph, a judgment on the Michelson experiment of 1886, which Voigt, after a correspondence with H. A. Lorentz in 1887 and 1888, has partly withdrawn in the article announced, namely in a footnote in Voigt (1888). According to Voigt's first judgment, the Michelson experiment must yield a null result, independently of whether the Earth transports the luminiferous aether with it (Fizeau's 1st aether hypothesis), or whether the Earth moves through an entirely independent, self-consistent universal [[luminiferous aether]] (Fizeau's 2nd aether hypothesis).
*{{Citation | author=Voigt, W. | year=1888 | journal=Annalen der Physik | title= Theorie des Lichts für bewegte Medien |pages= 370–396, 524–551 |volume=35 | issue=10 |doi=10.1002/andp.18882711011 |bibcode = 1888AnP...271..370V | url=https://zenodo.org/record/1423847 }}; In a footnote on p.&nbsp;390 of this article, Voigt corrects his earlier judgment, made in ''Göttinger Nachrichten'' No. 8, p.&nbsp;235 and p.&nbsp;236 (1887), and states indirectly that, after a correspondence with H. A. Lorentz, he can no longer maintain that in the case of the validity of Fizeau's 2nd aether hypothesis the Michelson experiment must yield a null result too.
*{{Citation | author=Bucherer, A. H.| year=1908 | title=Messungen an Becquerelstrahlen. Die experimentelle Bestätigung der Lorentz-Einsteinschen Theorie | journal=Physikalische Zeitschrift | volume =9 | issue=22 |pages =755–762}}; For Minkowski's statement see p.&nbsp;762.
*{{Citation | author=Lorentz, H.A | year=1916 | title=The theory of electrons  | url=https://archive.org/details/electronstheory00lorerich | place =Leipzig & Berlin| publisher=B.G. Teubner}}; See p.&nbsp;198.
* Lorentz 1904, [[s:en:Electromagnetic phenomena|Electromagnetic phenomena in a system moving with any velocity smaller than that of light]]

;Secondary sources
*{{Citation | author=Macrossan, M. N. | year=1986 | journal=Br. J. Philos. Sci. | title= A Note on Relativity Before Einstein  | url= http://espace.library.uq.edu.au/view/UQ:9560 |pages= 232–234 |volume=37 | issue=2 | doi=10.1093/bjps/37.2.232| citeseerx=10.1.1.679.5898 }}
* Ernst, Andreas & Hsu Jong-Ping (June 2001); [https://web.archive.org/web/20110716083015/http://psroc.phys.ntu.edu.tw/cjp/v39/211.pdf ''First Proposal of the Universal Speed of Light by Voigt in 1887''], pdf [[Chinese Journal of Physics]]

==External links==
{{commons category|Woldemar Voigt}}
* {{Internet Archive author |sname=Woldemar Voigt}}
*{{MathGenealogy |id=45011}}
* [http://www.mathpages.com/rr/s1-04/1-04.htm The relativity of light (MathPages)]
* [http://homepages.bw.edu/bachbib/script/bach1.pl?0=Voigt,%20Woldemar Bach expert Woldemar Voigt]

{{Authority control}}

{{DEFAULTSORT:Voigt, Woldemar}}
[[Category:1850 births]]
[[Category:1919 deaths]]
[[Category:19th-century German physicists]]
[[Category:Scientists from Leipzig]]
[[Category:Scientists from the Kingdom of Saxony]]
[[Category:Leipzig University alumni]]
[[Category:University of Königsberg alumni]]
[[Category:Academic staff of the University of Königsberg]]
[[Category:Academic staff of the University of Göttingen]]
[[Category:Foreign members of the Royal Society]]
[[Category:20th-century German physicists]]