298:(MMX) of 1887. Cohn's electrodynamics of moving bodies was based on the assumption that light travels within the Earth's atmosphere with a constant velocity - however, his theory suffered from internal failures. While the theory predicted the negative result of MMX within air, a positive result would be expected within vacuum. Another weak point stems from the fact, that his concept was formulated without the use of atoms and electrons. So after 1905 his theory was superseded by
317:(but also the concept of atoms) and argued that one can simply call it vacuum. He also maintained that one can use a frame of reference in which the fixed stars are at rest. As a heuristic concept this can be described as a material "aether", but in Cohn's opinion this would be only "metaphorical" and would not affect the consequences of his theory. He also incorporated the transformation equations
540:
He critically remarked that the distinction between "true time" and "local time" in
Lorentz's theory is artificial, because it cannot be verified by experiment. However, Cohn himself believed that the validity of Lorentz's theory is limited to optical phenomena, whereas in his own theory it is
293:
for moving bodies and proposed an independent theory. His alternative theory, which was based on a modification of the
Maxwell field-equations, was compatible to all relevant electrodynamic and optical experiments known at that time (1900–1904), including the
251:
and was married with Marie
Goldschmidt (1864–1950), with whom he had two daughters. Because of his Jewish descent he found himself forced to emigrate to Switzerland because of the pressure under the Nazi regime. He lived in
360:
was described by him as a consequence of the assumption that light propagates in spherical waves with constant velocity in all directions (a similar definition was already given by
Poincaré in 1900).
364:
Everywhere, where the propagation of radiation is not the object of measurement, we define identical moments of time at different points of Earth's surface, by treating the propagation of light as
193:
and was admitted as a private lecturer. From 1884 to 1918, he was a faculty member of the
University of Strasbourg and was nominated as an assistant professor on 27 September 1884. He dealt with
1019:
1024:
503:
are those measuring numbers being read at an "initially correct" measuring-rod (initially = when at rest), after it was introduced into the system and was accordingly deformed.
501:
917:
403:
888:
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376:
waves for every relatively resting and isotropic medium. This means: the "time" which actually serves us for the representation of terrestrial processes, is the "
427:
900:
871:
812:
Recueil de travaux offerts par les auteurs à H. A. Lorentz à l'occasion du 25ème anniversaire de son doctorat le 11 décembre 1900, Archives néerlandaises
530:
are those time intervals indicated by an "initially correctly ticking" clock, after it was inserted into the system and accordingly has changed its rate.
1029:
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170:
221:
541:
possible that mechanical clocks might indicate the "true" time. Later in 1911 (after his own theory was disproved), Cohn accepted the
1014:
708:
636:
1034:
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161:
on 28 September 1854. He was the son of August Cohn, a lawyer, and
Charlotte Cohn. At the age of 17, Cohn began to study
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237:
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at first, and then turned completely to theoretical physics. In 1918 he was nominated as an extraordinary professor.
174:
76:
285:
At the beginning of the 20th century, Cohn was one of the most respectable experts in the area of theoretical
344:
In 1904 he compared his theory with
Lorentz's mature 1904 theory, employing physical interpretations of the
825:
345:
217:
114:
453:
664:
213:
166:
545:
of "Lorentz and
Einstein" and wrote a summary on special relativity, which was applauded by Einstein.
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1004:
942:
849:
695:
Albert
Einstein's special theory of relativity. Emergence (1905) and early interpretation (1905–1911)
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542:
357:
310:
290:
194:
314:
190:
700:
233:
933:
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929:"Antikritisches zu Hrn. Wiens "Differentialgleichungen der Elektrodynamic für bewegte Körper""
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632:
338:
253:
325:
introduced by
Lorentz in 1895 into his theory, calling them the "Lorentzian Transformation" (
950:
857:
605:
121:
87:
823:
Cohn, E. (1901). "Über die Gleichungen des elektromagnetischen Feldes für bewegte Körper".
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205:
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Cohn's younger brother, Carl Cohn (1857–1931) was a successful overseas merchant from
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225:
220:. In 1935 he retired in Heidelberg where he lived until 1939. He resigned from the
186:
182:
126:
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these identical moments of time by assuming, that the propagation takes place in
181:. In Strasbourg, he graduated in 1879. From 1881 to 1884, he was an assistant of
257:
241:
201:
158:
154:
64:
46:
42:
810:
Cohn, E. (1900). "Über die Gleichungen der Electrodynamik für bewegte Körper".
586:
Darrigol, O., Olivier (1995). "Emil Cohn's electrodynamics of moving bodies".
248:
229:
954:
861:
142:
104:
836:"Ueber die Gleichungen des elektromagnetischen Feldes für bewegte Körper"
901:
Sitzungsberichte der Königlich Preussischen Akademie der Wissenschaften
872:
Sitzungsberichte der Königlich Preussischen Akademie der Wissenschaften
794:
Das Elektromagnetische Feld - Vorlesungen ĂĽber die Maxwell'sche Theorie
264:
178:
928:
835:
609:
216:. From June 1920, he gave lectures about theoretical physics at the
208:
by France, Cohn and his family were expelled from Strasbourg on the
309:
Regarding his own theory (developed in 1900 and 1901), he used the
212:
of 1918. In April 1919, he was nominated as a professor at the
341:
into the commonly used expression "Lorentz transformation".
898:
Cohn, E. (1904). "Zur Elektrodynamik bewegter Systeme II".
267:, who worked from 1921 until 1929 as a senator in Hamburg.
869:
Cohn, E. (1904). "Zur Elektrodynamik bewegter Systeme I".
141:(28 September 1854 – 28 January 1944), was a German
405:, for which the equations I'b to IVb hold, – not the "
972:, 117–136 (1911); auch als Broschüre veröffentlicht:
509:
456:
415:
386:
333:). In 1905 this name (for transformations valid to
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82:
72:
53:
28:
21:
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522:
495:
421:
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1020:Jewish emigrants from Nazi Germany to Switzerland
654:"The Optics and Electrodynamics of Moving Bodies"
449:
362:
260:, Switzerland, where he died at the age of 90.
1025:Academic staff of the University of Strasbourg
8:
981:Deutsches Museum - Abhandlungen und Berichte
918:On the Electrodynamics of Moving Systems II
976:, Berlin/Leipzig 1920, 4. Auflage (30 S.).
889:On the Electrodynamics of Moving Systems I
805:Das elektromagnetische Feld - Ein Lehrbuch
224:(DPG) together with other physicists like
18:
514:
508:
487:
474:
461:
455:
414:
385:
348:that were similar to those later used in
627:Electrodynamics from Ampére to Einstein
554:
673:
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185:at the physical institute. In 1884 he
171:Ruprecht Karl University of Heidelberg
240:, in protest at the despotism of the
7:
291:Lorentzian theory of electrodynamics
568:Archiv der Elektrischen Ăśbertragung
496:{\displaystyle x_{0}\ y_{0}\ z_{0}}
439:He also illustrated the effects of
222:Deutsche Physikalische Gesellschaft
313:to eliminate the known concept of
14:
974:Physikalisches ĂĽber Raum und Zeit
963:Physikalisches ĂĽber Raum und Zeit
768:Janssen/Stachel (2004), pp. 31-32
652:Janssen, M.; Stachel, J. (2004).
565:(1947). "Nachruf auf Emil Cohn".
447:by using moving rods and clocks.
1030:20th-century German physicists
1000:19th-century German physicists
803:; Second edition Berlin 1927:
337:orders in v/c) was altered by
289:. He was unsatisfied with the
1:
279:History of special relativity
631:. Oxford: Clarendon Press.
589:American Journal of Physics
331:Lorentz'sche Transformation
296:Michelson–Morley experiment
256:at first, and from 1942 in
1051:
623:Darrigol, Olivier (2000).
276:
986:(1), Berlin 1932 (29 S.).
368:. In optics, however, we
132:
93:
1015:Jewish German physicists
955:10.1002/andp.19043190619
916:Wikisource translation:
887:Wikisource translation:
862:10.1002/andp.19013120103
175:University of Strasbourg
77:University of Strasbourg
1035:People from Neustrelitz
979:"Faraday und Maxwell",
759:Darrigol (2000), p. 368
741:Cohn, 1904 II, p. 1408.
356:in 1905. For instance,
750:Cohn, 1904 I, p. 1299.
723:Cohn, 1901, pp. 98-99.
672:Cite journal requires
538:
524:
497:
437:
423:
399:
346:Lorentz transformation
330:
218:University of Freiburg
204:and the occupation of
115:University of Freiburg
826:Göttinger Nachrichten
777:Miller (1981), p. 182
691:Miller, A.I. (1981).
525:
523:{\displaystyle t_{0}}
498:
424:
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277:Further information:
214:University of Rostock
167:University of Leipzig
543:relativity principle
507:
454:
413:
384:
311:Principle of Economy
247:Cohn was a baptized
195:experimental physics
947:1904AnP...319..208C
854:1901AnP...312...29C
732:Cohn, 1900, p. 519.
602:1995AmJPh..63..908D
315:luminiferous aether
191:theoretical physics
934:Annalen der Physik
841:Annalen der Physik
520:
493:
441:length contraction
419:
398:{\displaystyle t'}
395:
354:special relativity
177:he began to study
169:. However, at the
834:Cohn, E. (1901).
791:Cohn, E. (1900).
482:
469:
422:{\displaystyle t}
254:Hasliberg-Hohfluh
200:After the end of
153:Cohn was born in
136:
135:
95:Scientific career
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927:Cohn, E (1904).
909:
908:(43): 1404–1416.
880:
879:(40): 1294–1303.
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122:Doctoral advisor
88:electromagnetism
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19:
16:German physicist
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596:(10): 908–915.
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535:Emil Cohn, 1904
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434:Emil Cohn, 1904
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411:
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350:Albert Einstein
304:Albert Einstein
300:Hendrik Lorentz
287:electrodynamics
281:
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238:Walter Kaufmann
206:Alsace-Lorraine
151:
139:Emil Georg Cohn
73:Alma mater
68:
62:
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57:28 January 1944
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339:Henri Poincaré
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83:Known for
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61:(aged 89)
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39:28 August 1854
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575:(1–2): 81–83.
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848:(1): 29–56.
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793:
785:Publications
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728:
719:
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665:cite journal
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407:general time
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284:
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246:
234:George Jaffé
226:Richard Gans
199:
183:August Kundt
152:
138:
137:
127:August Kundt
111:Institutions
94:
86:theoretical
59:(1944-01-28)
1010:1944 deaths
1005:1854 births
797:. Leipzig:
699:. 191-182.
258:Ringgenberg
242:Nazi regime
202:World War I
187:habilitated
159:Mecklenburg
155:Neustrelitz
65:Ringgenberg
47:Mecklenburg
43:Neustrelitz
994:Categories
941:(6): 208.
818:: 516–523.
563:Fritz Emde
378:local time
358:local time
323:t'=t-vx/c²
249:Protestant
230:Leo Graetz
35:1854-08-28
799:S. Hirzel
374:spherical
143:physicist
105:Physicist
23:Emil Cohn
829:: 74–99.
533:—
432:—
392:′
366:timeless
173:and the
943:Bibcode
850:Bibcode
598:Bibcode
549:Sources
319:x'=x-vt
302:'s and
265:Hamburg
179:physics
165:at the
707:
635:
481:
468:
370:define
327:German
101:Fields
657:(PDF)
970:XIII
906:1904
877:1904
705:ISBN
678:help
633:ISBN
443:and
321:and
306:'s.
271:Work
149:Life
54:Died
29:Born
965:",
951:doi
858:doi
846:312
606:doi
352:'s
335:all
189:in
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838:.
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