Felix Ehrenhaft

Felix Ehrenhaft ( born April 24, 1879 in Vienna, † March 4, 1952 ) was an Austrian physicist. He wrote papers on experimental charge measurements, the atomic physics and optical behavior of metal colloids.

Life

He was born in 1879 as son of the physician Leopold Ehrenhaft and his wife Louise Eggar, the daughter of a Hungarian industrialist, in Vienna. After graduating from the high school he studied physics and received his PhD in 1903 under the direction of Exner phil at the Physics Institute at the University of Vienna Dr. Viktor Lang, Ludwig Boltzmann and Franz Serafin Exner -. about the " optical behavior of the metal colloids, and the particle size ." From 1904 he was an assistant at I. Physics Institute under Franz Serafin Exner, 1905 was the Habilitation, 1912, he was associate professor, full professor in 1920 and head of the newly formed III. Physics Institute of the University of Vienna. 1938 had honorably as a Jew to leave Austria and continued his work first in England, then in the U.S. continues. In 1947 he returned to Vienna as Chief Executive of the I. Physics Institute. However, he had only the status of a guest professor, so he was denied in Vienna also a pension.

Ehrenhaft was married to the physicist Olga Steindler.

Importance

The key was his early involvement with the ultra-microscope by Henry Siedentopf and his teacher and Nobel Laureate in Chemistry Richard ZSIGMONDY. With a thesis on the well-known case of liquids, Brownian motion in gases, he was honored in 1910 by the Vienna Academy of Sciences with the Lieben Prize. Simultaneously and independently by Robert Millikan in 1909, he developed a now be regarded as a classical method to determine the charge of small particles. While Millikan examined the movement of liquid droplets in an electric field, Ehrenhaft worked with solid aerosol particles whose movement was much harder to predict because of their irregular shape than the spherical drops of Millikan. For his efforts to solve the problem of elementary charges he received from the Vienna Academy of Sciences, 1917 Haitinger price. However, the international recognition (including a Nobel Prize ) received mostly Millikan.

From 1930 sliding off the mainstream of classical physics was seen with a year-long involvement in a scientific dispute. Since he was also very concerned about his public approval, there were many anecdotes about him. His house was a meeting place of scientists and artists in Vienna, and on one occasion he invited Albert Einstein to give lectures to Vienna.

The course " Introduction to Physics ", the Honorable held in 1947 after his return to the University of Vienna, was impressive and enjoyable. You could, however, be confusing for prospective students because it contradicted in material respects, the "accepted body of knowledge ", ie the general doctrine:

• Ehrenhaft was convinced that electric charges in the nature does not always integer multiples of the elementary electric charge e, the charge of the electron (1.6 * 10-19 C) are, but that there are also smaller loads.

• Ehrenhaft was convinced that with a permanent magnet, the two poles are not always equally strong, but that there are also individual magnetic poles, that is, particles which have a surplus of the north or south magnetism.

In Ehrenhaft lecture most impressive experiments have shown, inter alia, to " photopheresis ", ie the movement of small aerosol particles under the influence of light. There was just to admire paths, circular paths and helical paths (see Ehrenhaft articles from the years 1951 and 1952, see below). Only many years later was able to show by calculation, how to explain this complicated movements by radiometer forces ( radiometer called the small wing wheel blackened in a glass ball under low air pressure on one side, which rotate in the light of Hans Rohatschek ( one of his former assistants) ).

The Ehrenhaft 's results of non - integrality of e and the apparent individual magnetic poles can be loud Rohatschek (see below) today explained by photopheresis in the electric or magnetic field. Even at the end of the 1940s he sought in Vienna for magnetic monopoles in the cosmic radiation.

Paradoxically, the search was by particles with a charge smaller than e, and the search for magnetic monopoles few years after Ehrenhaft death date again. When it turned out that protons and neutrons are made of quarks with a charge or, they were looking for such free particles, but without success: apparently the quarks can move freely only inside the atomic nucleus. The search for individual magnetic poles is now (2006 ) at the Tevatron particle accelerator in the United States intensively operated at the highest energies (see below), but so far without success.

Writings

• Felix Ehrenhaft: The optical behavior of the metal colloids and their particle size, 1903.
• Felix Ehrenhaft: On the measurement of quantities of electricity, which seem to be less than the charge of the monovalent hydrogen ion or electron and deviate from its multiples, quays. Acad. Vienna, Sitzber. math. - nat. Kl 119 (IIa ), pp. 815-867, 1910
• Felix Ehrenhaft: The micro-magnetic field, 1926.
• Felix Ehrenhaft: The longitudinal and transverse electric and magnetophoresis, Phys. Time. 31, pp. 478-485, 1930
• Felix Ehrenhaft: Stationary Electric and Magnetic Fields in Beams of Light, Nature 147: 25 (4 January 1941).
• Felix Ehrenhaft: The Magnetic Current, Science 94: pp. 232-233 (5 September 1941).
• Felix Ehrenhaft and Leo Banet: The Magnetic Ion, Science 96: pp. 228-229 (4 September 1942).
• Felix Ehrenhaft: The Magnetic Current in gas, Physical Review 61: p 733 ( 1942).
• Felix Ehrenhaft: Decomposition of Matter Through the Magnet ( Magnetolysis ), Physical Review 63: p 216 ( 1943).
• Felix Ehrenhaft: Magnetolysis and the Electric Field Around the Magnetic Current, Physical Review 63: pp. 461-462 ( 1943).
• Felix Ehrenhaft: New Experiments about the Magnetic Current, Physical Review 65: pp. 62-63 (1944).
• Felix Ehrenhaft: The Magnetic Current, Nature 154: pp. 426-427 (September 30, 1944).
• Felix Ehrenhaft: Via the photopheresis, the true magnetic charge and the helical motion of matter in fields ( For a review of his life's work part 1), Acta Physica Austriaca 4: pp. 461-488 ( 1951).
• Felix Ehrenhaft: Via the photopheresis, the true magnetic charge and the helical motion of matter in fields ( For a review of his life's work part 2), Acta Physica Austriaca 5: pp. 12-29 ( 1952).

Swell

• Berta Karlik and Erich Schmid: Franz S. Exner and his circle, Austrian Academy of Sciences, Vienna, 1982
• Hans Rohatschek: History of photopheresis, in: O. Preining et al, ed. History of Aerosol Science, Proceedings of the Symposium on Aerosol Science, Austrian Academy of Sciences, Vienna, 2000
• Joseph Brown Beck: The other physicists. The life of Felix Ehrenhaft of Vienna, Graz, Leykam, 2003, 164 pages, b / w illustrations ISBN 3-7011-7470-9