Walter Kaufmann

Walter Kaufmann

German physicist
Date of Birth: 05.06.1871
Country: Germany

  1. Biography of Walter Kaufmann
  2. Education and Early Career
  3. Later Career and Contributions
  4. Kaufmann's Experiments and the Theory of Relativity

Biography of Walter Kaufmann

Walter Kaufmann was a German physicist who played a significant role in the discussion of the special theory of relativity (STR) in the early 20th century. His experiments, which investigated the dependence of an electron's inertia on its velocity, were instrumental in the understanding of this theory.

Education and Early Career

Kaufmann initially studied engineering at the Berlin and Munich Technical Universities. He then pursued a course in physics at the universities of Berlin and Munich. In 1894, he successfully defended his dissertation and became an extraordinary professor of physics at the University of Bonn from 1899 onwards.

Later Career and Contributions

In 1908, Kaufmann received an invitation to become an ordinary professor of experimental physics at the University of Königsberg and the director of the Physical Institute there. He held these positions until his retirement in 1935. Kaufmann's works covered various fields such as mechanics, aerodynamics, hydrodynamics, and atomic physics.

In 1897, Kaufmann, along with J. J. Thomson, measured the ratio of charge to mass for cathode rays. Although their results were similar, Kaufmann was cautious in his conclusions, and Thomson received the credit for the discovery of the electron.

Even before the development of the special theory of relativity, Kaufmann conducted a series of experiments from 1901 to 1903, which established for the first time the dependence of the ratio of charge to mass for an electron on its velocity. At that time, this effect was interpreted as the presence of an additional "electromagnetic" mass for the electron. Three different formulas were proposed to account for the mass-velocity relationship by Max Abraham, Alfred Bucherer, and Hendrik Lorentz.

Kaufmann's Experiments and the Theory of Relativity

Towards the end of 1905, after Einstein published the theory of relativity, Kaufmann conducted new measurements, improving their accuracy compared to his previous experiments. The published results of these experiments did not confirm Lorentz's formulas, which were included in the theory of relativity, thus casting doubt on the validity of the principle of relativity for electrodynamics.

Kaufmann himself had been skeptical of the theory of relativity from the beginning and declared that his experiments supported Max Abraham's alternative theory instead of Einstein's. However, several independent measurements conducted by Alfred Bucherer (1908), Neumann (1914), and others, demonstrated that the principle of relativity holds true for electrodynamics as well, leading to the rejection of Abraham's theory.

The question of whether the accuracy of Kaufmann's experiments was sufficient to draw such conclusions during that time remains debatable.