Walter Kaufmann (physicist)

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

Life

Kaufmann, who was born into a Jewish family, but was baptized, studied 1890/91 mechanical engineering at the Technical Universities of Berlin and Munich, since 1892 physics at the Universities of Berlin and Munich; In 1894 he received his doctorate. From 1896 he worked as an assistant at the Physics Institutes of the Universities of Berlin and Göttingen. Kaufmann completed his habilitation in 1899 and 1902 and was an associate professor of physics at the Rheinische Friedrich- Wilhelms University in Bonn. After a new activity at the Berlin Institute of Physics in 1907 he followed a call as Full Professor of Experimental Physics and Head of the Physics Institute at the Albertina in Königsberg. In office year 1922/23, Kaufmann was rector of the University of Königsberg. In 1935, he was transferred to retire early because of his Jewish origin. After the Second World War, he served as visiting professor at the University of Freiburg / Breisgau.

Experiments on relativistic mass

First provisions of the ratio ( specific charge ), he led in 1897, where he was about to prove the electron as a particle experimentally, but he interpreted the results as insufficient to decide whether it is in fact but are particles or waves. In the same year Joseph John Thomson was able to establish their own experiments using the electron as a particle, and thus Thomson is regarded as the discoverer of the electron.

Inspired by theoretical predictions of Joseph John Thomson ( 1881), George Frederick Charles Searle ( 1987) and Hendrik Antoon Lorentz (1900 ) over the increase in mass of accelerated electric charges led Kaufmann 1901 an experiment, in which he for the first time the velocity dependence of the electromagnetic inertia, mass of the electron proved. Max Abraham (1902 ), however, recognized in his attempt to substantiate the experiments of Kaufmann theoretically that the formula of Searle to was valid as at merchant's experiments only for accelerations in the direction of movement, and not perpendicular. He led therefore ( as it already Lorentz 1899), in addition to the longitudinal and a transverse mass one. In the works of 1902-1903 this circumstance by Kaufmann has now also taken into account. In addition, the merchant attempts have been interpreted to mean that only a " seeming " electromagnetic mass, and there is no "real" mechanical mass. However, his measurements were not accurate enough to distinguish between the predictions of the transverse mass distribution in Lorentz's ether theory and the theory of Abraham.

The end of 1905, he still led by more precise experiments. Here there is also the first time in the literature a discussion of the recently published Special Relativity Albert Einstein. Although built from completely different starting conditions and logically satisfying that she was " observation equivalent" to the theory of Lorentz, which is why Kaufmann of the principle of relativity as the " Lorentz - Einstein " speaks basic conception. His results spoke now in his opinion for the theory of Abraham, and presented a refutation of the principle of relativity dar. For some years this was a serious argument against the theories of Lorentz and Einstein, although Adolf Bestelmeyer in 1906 compiled the results into question.

Alfred Bucherer (1908), Neumann ( 1914) and others, however, came to results, which in their view better suited to the " Lorentz -Einstein " theory. However, later ( 1938) it was found that the Kaufmann- Bucherer - Neumann experiments, although in general the velocity dependence of the mass confirmed, but were not accurate enough to distinguish the Lorentz - Einstein mass concept of Abraham 's. This has been achieved with this type of experiments until 1940. (However, this problem was only for this type of experiments. Investigations of the fine structure of the hydrogen lines already in 1917 was a much more accurate confirmation of the Lorentz - Einstein formula, and thus the refutation of Abraham 's theory, be provided. )

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