After the end of World War I and the occupation of Alsace-Lorraine by France, Cohn and his family were expelled (on the Christmas Eve 1918) from Strasbourg. In April 1919, he was nominated as a professor at the University of Rostock. From June 1920, he gave lectures about theoretical physics at the University of Freiburg. In 1935 he retired in Heidelberg where he lived until 1939. He resigned from the Deutsche Physikalische Gesellschaft (DPG) together with other physicists like Richard Gans, Leo Graetz, George Jaffé, Walter Kaufmann, in protest at the despotism of the NS-regime.
Cohn was a baptized Protestant and was married with Marie Goldschmidt (1864 - 1950), with whom he had two daughters. Because of his Jewish descent he found himself forced in 1939 under the pressure of the NS-regime to emigrate to Switzerland. He lived in Hasliberg-Hohfluh at first, and from 1942 in Ringgenberg, Switzerland, where he died at the age of 90.
Cohn’s younger brother Carl Cohn (1857-1931) was a successful overseas-merchant from Hamburg, who worked from 1921 until 1929 as a senator in Hamburg.
At the change of the 19. to the 20. Century, Emil Cohn was one of the most respectable experts in the area of theoretical electrodynamics. He was unsatisfied with the Lorentzian theory of electrodynamics 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, incl. the Michelson-Morley experiment.
Some of his insights entailed certain aspects of special relativity, in particular some aspects of the interpretation of the Lorentz transformation by. After Henri Poincaré but before Albert Einstein, he interpreted Lorentz's local time as the result of clock synchronisation by light signals (1904). However, he believed that mechanical clocks still show the "true" time. He also eliminated the luminiferous aether and replaced it like Ernst Mach by the fixed stars (1901). Because of internal failures of his theory (like different light speeds in different directions) his theory was superseded by Lorentz's and Einstein's.
Double vision: for this Brookhaven family, the past and present often merge, and they can look next door and see a house exactly like their own vintage beauty.
Jan 01, 2011; Karen and David Braden of Brookhaven may technically own their house on historic South Jackson Street, but they sometimes feel...