Walter Kaufmann (physicist)

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Walter Kaufmann

Walter Kaufmann (born June 5, 1871 in Elberfeld (now part of Wuppertal ), † January 1, 1947 in Freiburg im Breisgau ) was a German physicist . With the first experimental proof of the increase in the inertial mass of the electron with increasing speed, Kaufmann made an important contribution to the preparation of the modern theory of relativity .

Life

Kaufmann, who came from a Jewish family but was baptized, was the son of the banker Albert Kaufmann († 1899) and Bertha Samuel († 1900). He attended the municipal high school in Elberfeld up to Ober-Tertia. After the family moved to Berlin, he went to the Königliche Wilhelms-Gymnasium , where he passed his school leaving examination at Easter 1890. This was followed by a six-month practical training in a state railway workshop. From 1890/91 he studied mechanical engineering at the Technical Universities of Berlin and Munich, and since 1892 physics at the universities of Berlin and Munich; In 1894 he received his doctorate in Munich. From 1896 he worked as an assistant at the physical institutes of the universities of Berlin and Göttingen. Kaufmann completed his habilitation in 1899 and in 1902 became associate professor of physics at the Rheinische Friedrich-Wilhelms-Universität in Bonn . After a renewed activity at the Berlin Physics Institute, he followed a call in 1907 as full professor for experimental physics and head of the Physics Institute at the Albertina in Königsberg . In the 1922/23 year of office, Kaufmann was rector of the University of Königsberg. In 1935 he was given early retirement due to his Jewish origins. After the Second World War he taught as a visiting professor at the University of Freiburg / Breisgau.

He was married twice. His first wife Frieda Kuttner (1879–1928), whom he married in 1900, died in 1928. This marriage resulted in three sons and two daughters. In 1932 he married Else Bath. With her he had a son. He is the father of the geologist and paleontologist Rudolf Kaufmann , who was shot in Lithuania around 1941. A second son died of starvation in the Theresienstadt concentration camp .

Experiments on relativistic mass

He carried out the first determinations of the ratio ( specific charge ) in 1897, when he was on the verge of experimentally demonstrating the electron as a particle, but he interpreted the results as insufficient to decide whether it was actually a particle or a wave. In the same year Joseph John Thomson was able to establish the electron as a particle by means of his own experiments, and thus Thomson is considered the discoverer of the electron.

Inspired by theoretical predictions by Joseph John Thomson (1881), George Frederick Charles Searle (1897), and Hendrik Antoon Lorentz (1900) about the increase in the mass of accelerated electrical charges, Kaufmann carried out an experiment in 1901 in which he for the first time investigated the velocity dependence of inert, electromagnetic Proved the mass of the electron. However, Max Abraham (1902) recognized in his attempt to theoretically support Kaufmann's experiments that Searle's formula was only valid for accelerations in the direction of motion, and not perpendicular to it, as in Kaufmann's experiments. He therefore introduced (like Lorentz before him in 1899), in addition to the longitudinal also a transversal mass. In the works from 1902–1903, Kaufmann also took this into account. In addition, Kaufmann's experiments were interpreted in such a way that only an “apparent” electromagnetic mass and no “real” mechanical mass exist. However, his measurements were not yet accurate enough to distinguish between the predictions of transverse mass in Lorentz's ether theory and Abraham's theory.

At the end of 1905 he carried out even more precise experiments. Here, for the first time in literature, there is a discussion of Albert Einstein's special theory of relativity, which was published shortly before . Although it is based on completely different assumptions and is also logically more satisfactory, it is "observationally equivalent" to Lorentz's theory, which is why Kaufmann speaks of the principle of relativity as the "Lorentz-Einsteinian" basic conception. In his opinion, his results now spoke in favor of Abraham's theory and represented a refutation of the principle of relativity. For several years this was a heavy counter-argument for the theories of Lorentz and Einstein, although Adolf Bestelmeyer questioned the results as early as 1906.

However, Alfred Bucherer (1908), Neumann (1914) and others came to results which, in their opinion, fit better with the “Lorentz-Einstein” theory. However, later (1938) it was found that the Kaufmann-Bucherer-Neumann experiments generally confirmed the velocity dependence of the mass, but were not precise enough to distinguish the Lorentz-Einstein mass concept from the Abrahamic one. It wasn't until 1940 that this type of experiment succeeded. (However, this problem only existed for this type of experiment. When investigating the fine structure of the hydrogen lines , a much more precise confirmation of the Lorentz-Einstein formula and thus the refutation of the Abrahamian theory could be provided as early as 1917.)

Kaufmann built the first rotating high pressure vacuum pump.

See also

Publications

  • Magnetism and electricity , in Müller-Pouillet Textbook of Physics 1909

literature

  • Hans Kangro :  Kaufmann, Walter. In: New German Biography (NDB). Volume 11, Duncker & Humblot, Berlin 1977, ISBN 3-428-00192-3 , p. 352 f. ( Digitized version ).
  • German Biographical Encyclopedia (DBE) (Rudolf Vierhaus, Ed.), 2nd edition, Vol. 5, Munich 2006, p. 541.
  • Johann Christian Poggendorff, Biographical-Literary Concise Dictionary ; Vol. IV, 1883-1904, Part 1: 1904; Vol. V, 1904-1922, Part 1: 1925.
  • Joseph Walk (ed.): Short biographies on the history of the Jews 1918–1945. Edited by the Leo Baeck Institute, Jerusalem. Saur, Munich 1988, ISBN 3-598-10477-4 , p. 190.
  • Christian Tilitzki: The Albertus University of Königsberg: Its history from the founding of the empire to the fall of the province of East Prussia (1871-1945). Volume 1: 1871-1918, Walter de Gruyter, 2012, p. 560
  • Walther Kossel : Walter Kaufmann † , In: Die Naturwissenschaften 34 (1947), Heft 2, S. 1f. ( Digitized version )

swell

  1. ^ A b Miller, AI: Albert Einstein's special theory of relativity. Emergence (1905) and early interpretation (1905-1911) . Addison-Wesley, Reading 1981, ISBN 0-201-04679-2 .
  2. ^ Janssen, M., Mecklenburg, M .: From classical to relativistic mechanics: Electromagnetic models of the electron . In: VF Hendricks et al. (Ed.): Interactions: Mathematics, Physics and Philosophy . Springer, Dordrecht 2007, pp. 65-134.

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personal data
SURNAME Kaufmann, Walter
BRIEF DESCRIPTION German physicist
DATE OF BIRTH June 5, 1871
PLACE OF BIRTH Elberfeld
DATE OF DEATH January 1, 1947
Place of death Freiburg in Breisgau