Background
Walter Kaufmann was born on June 5, 1871, in Elberfeld, Germany.
Technical University of Berlin, Berlin, Germany
Kaufmann studied at the Technical University of Berlin.
Technical University of Munich, Munich, Germany
Kaufmann studied at the Technical University of Munich.
umboldt University of Berlin, Berlin, Germany
Kaufmann studied at the Humboldt University of Berlin.
udwig Maximilian University of Munich, Munich, Germany
Kaufmann studied at the Ludwig Maximilian University of Munich.
Walter Kaufmann was born on June 5, 1871, in Elberfeld, Germany.
Kaufmann studied mechanical engineering at the technical universities of Berlin and Munich. From 1892 he studied physics at the Universities of Berlin and Munich, attaining a doctorate in 1894.
In 1896 Kaufmann was assistant in the Physics Institute at Berlin; three years later he accepted a similar position at Göttingen, later being promoted to Privatdozent. Kaufmann became associate professor at Bonn in 1903 and full professor and director of the Physics Institute of Königsberg in 1908; he retired in 1935 as professor emeritus. He then moved to Freiburg, where until his death he served occasionally as visiting professor.
(The book contains Kaufmann's work Die Entwicklung des Ele...)
1901While at Berlin in 1896-1898 Kaufmann began research on the magnetic deflection of cathode rays, attempting a first approximation of the ratio of electron charge to mass (elm). During this period a controversy arose over whether electrons, believed to be the ultimate constituents of matter, could have “apparent” mass in addition to “real” (material) mass. Apparent mass would be the “electromagnetic mass” gained from the interaction of the moving charge with its own field. Kaufmann’s major works were concerned primarily with attempts to measure and characterize this electromagnetic mass of electrons.
During the Göttingen years, 1899-1902, Kaufmann conducted research on the magnetic and electric deflection of radium emanations - then known as Becquerel rays. From the Curies, he obtained several radioactive particles of radium chloride and set about measuring the e/m ratio. Since these newly discovered rays had velocities approaching the speed of light, it was assumed that the maximum possible electromagnetic charge was imparted to them. On the basis of his initial e/m measurements in 1901, Kaufmann asserted that the apparent mass was appreciably larger than the real mass - by an estimated magnitude of at least three to one. His successful measurements apparently were made possible by his experimental apparatus, which attained a more complete vacuum than other experimenters could produce in their vacuum tubes.
About the same time a fellow professor at Göttingen, Max Abraham, had formulated a theory of electrons assuming the electromagnetic mass as the total mass of rigid, spherical electrons. Kaufmann adopted this hypothesis. By 1902 Kaufmann produced experimental evidence that the mass of electrons was entirely electromagnetic, that is, that electromagnetic mass constituted the total mass of electrons. More importantly, in these same investigations, he presented evidence that the mass of electrons was dependent on their velocity, noting that this dependence was accurately calculated by Abraham’s theoretical formula. Thus, a sacrosanct Newtonian principle - that mass was invariant with velocity - was contradicted by Kaufmann’s experimental data. By March 1903 Kaufmann confidently declared that not only the Becquerel rays but also the cathode rays consisted of electrons having a mass entirely electromagnetic.
By May 1904, H. A. Lorentz had developed a theory of electrons as being contractable with velocity and in the direction of motion. This view of electrons later became associated with Einstein’s theory of relativity. In the same year, Alfred Bucherer advanced a view intermediate between Abraham’s theory and that of Lorentz. He believed electrons were elastic and could be deformed or contracted in the direction of motion but would maintain a constant volume.
During his years at Bonn, Kaufmann undertook a new series of measurements in an attempt to corroborate one of the three rival theories. Upon completion of this work, and after requesting a thorough review by Sommerfeld, he published his results in 1906. He found that both Abraham’s and Bucherer’s theories were within the limits of experimental error for his measurements, but that the Lorentz-Einstein theory was not. He concluded that Lorentz’s theory was thus refuted and that Einstein’s theory of relativity was faulty in this respect.
Near the end of 1906, the significance of Kaufmann’s measurements was challenged by Max Planck. Developing his own mathematical calculations, Planck reached the tentative conclusion that neither Lorentz’s nor Abraham’s theory conformed closely to Kaufmann’s data. He contended that a different interpretation of Kaufmann’s measurements might conceivably place Lorentz’s theory in a more favorable position. In 1907 Einstein reviewed Kaufmann’s data, noting that these data could conform to relativity theory. He objected to the theoretically limited scope of Abraham’s theory - it could not explain as many phenomena as could the theory of relativity. By 1908 Bucherer published experimental data, of greater accuracy than Kaufmann’s measurements; these new data supported the Lorentz-Einstein viewpoint. After 1906 Kaufmann apparently abandoned further investigations in this area.
As early as 1901 Kaufmann reviewed the history of electron theory in his address “Die Entwicklung des Elektronenbegriffs,” delivered at the seventy-third Naturforscher Versammlung at Hamburg. He noted the fruitless efforts in the past to reduce electrical phenomena to mechanical phenomena and advocated reversing the process by attempting to reduce mechanics to electrical principles. Acknowledging the contributions of Lorentz, J. J. Thomson, and W. Wein in this direction, Kaufmann reasoned that if atoms consisted of conglomerates of electrons, then their inertia resulted as a matter of course.
It is not known whether Kaufmann was married or not; virtually nothing is known about his family either.