Felix Honorable

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

Life

He was born in Vienna in 1879 as the son of the doctor Leopold Ehrenhaft and his wife Louise Eggar, the daughter of a Hungarian industrialist. After graduating from high school, he studied physics at the University of Vienna with Viktor von Lang , Ludwig Boltzmann and Franz-Serafin Exner and obtained his doctorate in 1903 at the Physics Institute under the direction of Exner. phil. on the optical behavior of the metal colloids and their particle size . From 1904 he was assistant at the I. Physikalisches Institut under Franz-Serafin Exner, in 1905 he received his habilitation, in 1912 he became an associate professor, in 1920 he was a full professor and chairman of the newly founded III. Physical Institute of the University of Vienna. In 1938 Ehrenhaft had to leave Austria as a Jew and continued his work, first in England, then in the USA. In 1947 he returned to Vienna as head of the I. Physics Institute. However, he only had the status of a visiting professor, which is why he was refused a pension in Vienna. He was buried at the Döblinger Friedhof .

Ehrenhaft was married to the physicist Olga Ehrenhaft-Steindler .

meaning

The decisive factor was his early involvement with the ultramicroscope by Henry Siedentopf and his teacher and Nobel Prize winner for chemistry Richard Zsigmondy . In 1910, he was awarded the Lieben Prize by the Vienna Academy of Sciences for his work on the Brownian molecular motion in gases, which is known in liquids . At the same time and independently of Robert Millikan , in 1909 he developed a method for determining the charge of small particles that is now considered to be classic. While Millikan investigated the movement of liquid droplets in an electric field, Ehrenhaft worked with solid aerosol particles , the movement of which, because of their irregular shape, was much more difficult to predict than with the spherical drops from Millikan. For his efforts to solve the problem of elementary charges, he received the Haitinger Prize from the Vienna Academy of Sciences in 1917 . Most international recognition (including a Nobel Prize) was received by Millikan.

From 1930 onwards a slide from the mainstream of classical physics could be seen with years of involvement in a scientific dispute. Since he was also very concerned about his public reputation, there were many anecdotes about him. His house was a meeting place for scientists and artists in Vienna, and on one occasion he invited Albert Einstein to give lectures in Vienna.

The lecture “Introduction to Physics”, which Ehrenhaft held from 1947 after his return to the University of Vienna, was impressive and enjoyable. However, it could be confusing for prospective students, as it contradicted the "accepted body of knowledge", i.e. the general doctrine, in essential aspects:

  • Ehrenhaft was convinced that electric charges in nature are not always integral multiples of the elementary electric charge e , the charge of the electron (1.6 * 10 −19 C), but that there are also smaller charges.
  • Ehrenhaft was convinced that the two poles of a permanent magnet are not always equally strong, but that there are also individual magnetic poles ( magnetic monopole ), i.e. H. Particles that have an excess of north or south magnetism.

Most impressive experiments were shown in Ehrenhaft's lecture, including a. for "photophoresis", ie for the movement of small aerosol particles under the influence of light. There were straight orbits, circular orbits and screw orbits to admire (see Ehrenhaft's article from 1951 and 1952, see below). It was not until many years later that Hans Rohatschek (one of his former assistants) was able to show by calculation how these complicated movements could be explained by radiometer forces (radiometers are the small vaned wheels in a glass ball under low air pressure, blackened on one side, which rotate in the light ).

According to Rohatschek (see below), Ehrenhaft's results of the non-integer value of e and the apparent individual magnetic poles can also be explained today by photophoresis in an electric or magnetic field. At the end of the 1940s he was still looking for magnetic monopoles in the cosmic radiation in Vienna .

Paradoxically, the search for particles with a charge smaller than e and the search for magnetic monopoles became relevant again a few years after Ehrenhaft's death. When it turned out that protons and neutrons consist of quarks with a charge or , one looked for such free particles, but without success: apparently the quarks can only move freely inside hadrons . The search for individual magnetic poles has been intensively pursued at the Tevatron particle accelerator in the USA since 2006 (see below), but so far without success. As of 2015, the MoEDAL (Monopole and Exotics Detector at the LHC ) at CERN in the canton of Geneva in Switzerland will again be looking for magnetic monopoles.

Fonts

  • Felix Ehrenhaft: The optical behavior of metal colloids and their particle size , 1903.
  • Felix Ehrenhaft: About the measurement of quantities of electricity that appear to be smaller than the charge of the monovalent hydrogen ion or electron and differ from its multiples , Kais. Akad. Wiss. Vienna, registered office. math.-nat. Kl. 119 (IIa) pp. 815-867, 1910
  • Felix Ehrenhaft: The Micromagnetic Field , 1926.
  • Felix Ehrenhaft: The longitudinal and transversal electro- and magnetophoresis , Phys. Time. 31, pp. 478-485, 1930
  • Felix Ehrenhaft: Stationary Electric and Magnetic Fields in Beams of Light , Nature 147: 25 (January 4, 1941).
  • Felix Ehrenhaft: The Magnetic Current , Science 94: pp. 232-233 (September 5, 1941).
  • Felix Ehrenhaft and Leo Banet: The Magnetic Ion , Science 96: pp. 228-229 (September 4, 1942).
  • Felix Ehrenhaft: The Magnetic Current in Gases , 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: Further Facts Concerning the magnetic Current , Physical Review 64: p. 43 (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: About the photophoresis, the true magnetic charge and the helical movement of matter in fields (review article about his life's work part 1), Acta Physica Austriaca 4: p. 461–488 (1951).
  • Felix Ehrenhaft: About photophoresis, the true magnetic charge and the helical movement of matter in fields (review article about his life's work, part 2), Acta Physica Austriaca 5: pp. 12–29 (1952).

literature

  • Berta Karlik and Erich Schmid: Franz S. Exner und seine Kreis , Verlag der Österreichischen Akademie der Wissenschaften, Vienna, 1982
  • Hans Rohatschek: History of Photophoresis , in: O. Preining et al., Ed .: History of Aerosol Science, Proceedings of the Symposium on Aerosol Science , Verlag der Österreichischen Akademie der Wissenschaften, Vienna, 2000
  • Joseph Braunbeck: The other physicist. The life of Felix Ehrenhaft Vienna , Graz, Leykam, 2003, 164 pages, b / w illustrations ISBN 3-7011-7470-9
  • B. Schwarzschild: Search for magnetic monopoles at the Tevatron sets new upper limit on their production , Physics Today 59, No. 7, p. 16 (July 2006)
  • Christian H. Stifter: Between spiritual renewal and restoration. American plans for denazification and democratic reorientation and the post-war reality of Austrian science 1941–1955 . Böhlau, Vienna - Cologne - Weimar 2014, pp. 393–403. [1]

Web links

Individual evidence

  1. ↑ Thirring Lust am Forschen , Seifert Verlag 2008, p. 221.
  2. ^ Grave site Felix Ehrenhaft , Vienna, Döblinger Friedhof, Group I20, Row G2, No. 20.
  3. ^ Ehrenhaft-Steindler-Platz in the Vienna History Wiki of the City of Vienna
  4. ↑ Partly by his student Walter Thirring Lust am Forschen , Seifert Verlag, 2008, p. 215ff. reproduced.
  5. ^ Richard Webb: Pole alone: ​​The quest for a north without a south . New Scientist magazine, issue 2982, pp. 34-37, August 13, 2014.
personal data
SURNAME Honorable, Felix
BRIEF DESCRIPTION Austrian physicist
DATE OF BIRTH April 24, 1879
PLACE OF BIRTH Vienna
DATE OF DEATH March 4th 1952
Place of death Vienna