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Walter Kaufmann

Walter Kaufmann (June 5, 1871, Elberfeld - January 1, 1947, Freiburg im Breisgau) was a German physicist. He is most well-known for his first experimental proof of the velocity dependence of mass, which was an important contribution to the development of modern physics, including special relativity.



In 1890/91 he studied mechanical engineering at the technical universities of Berlin and Munich, since 1892 he studied physics at the Universities of Berlin and Munich and in 1894 he attained a doctorate. Starting from 1896 he worked as an assistant at the physical institutes of the Universities of Berlin and Göttingen. Kaufmann habilitated in 1899 and became a professor extraordinarius of physics in at the University of Bonn. After a renewed activity at the Berliner Physikalisches Institut he followed a call as professor ordinarius for experimental physics and leader of the physical institute at the Albertina in Königsberg, where he taught up to his retirement in 1935. Subsequently, he worked as a guest lecturer at the University of Freiburg.[1]

Measurements of velocity dependence of mass

His early work (1901-1903) confirmed for the first time the velocity dependence of the electromagnetic mass of the electron (later called relativistic mass). However, those measurements were not precise enough to differentiate between the Lorentz ether theory of Hendrik Antoon Lorentz and the theory of Max Abraham.

At the end of 1905 he performed experiments that were still more exact. Here Kaufmann was the first to discuss Albert Einstein's theory of special relativity and argued, that although Einstein's theory is based on completely different conditions and is also logically more satisfying, the theory is observationally equivalent to Lorentz's theory. Therefore he spoke of the theory of "Lorentz-Einstein". It is notable that Kaufmann himself interpreted the results of his experiments as a confirmation of Abraham's theory, and a refutation of the Lorentz-Einstein principle of relativity, which for some years weighed heavily against the theories of Lorentz and Einstein. However, Kaufmann's results were criticized by Max Planck and Adolf Bestelmeyer in 1906.

So physicists like Alfred Bucherer (1908), Neumann (1914) and others, repeated those experiments and arrived at results which apparently confirmed the "Lorentz Einstein" theory and disproved Abraham's theory. However, it was later pointed out that the Kaufmann-Bucherer-Neumann experiments after 1904 were also not precise enough to distinguish among the theories.[2] Abraham's theory was not disproved until 1940.[3] For a historical analysis see the works of Miller[4] and Janssen/Mecklenburg.[5]

See also


  1. ^ Hans Kangro: Kaufmann, Walter. In: Neue Deutsche Biographie (NDB). Band 11, Duncker & Humblot, Berlin 1977, S. 352 f. (German)
  2. ^ Zahn, C. T. and Spees, A. A. (1938), "A Critical Analysis of the Classical Experiments on the Variation of Electron Mass", Physical Review 53: 511‚Äď521  
  3. ^ Rogers, M. M. et al. (1940), "A Determination of the Masses and Velocities of Three Radium B Beta-Particles", Physical Review 57: 379‚Äď383  
  4. ^ Miller, A.I. (1981), Albert Einstein‚Äôs special theory of relativity. Emergence (1905) and early interpretation (1905‚Äď1911), Reading: Addison‚ÄďWesley, ISBN 0-201-04679-2  
  5. ^ Janssen, M., Mecklenburg, M. (2007), From classical to relativistic mechanics: Electromagnetic models of the electron, in V. F. Hendricks, et al., , Interactions: Mathematics, Physics and Philosophy (Dordrecht: Springer): 65‚Äď134,  


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