Erwin Freundlich

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Einstein Tower on Telegrafenberg in Potsdam .

Erwin Finlay-Freundlich (born May 29, 1885 in Wiesbaden-Biebrich ; † July 24, 1964 in Wiesbaden ) was an astrophysicist and the brother of Herbert Finlay Freundlich .

life and work

Freundlich was the son of a Scottish mother, Ellen Elizabeth Finlayson, and Friedrich Philipp Ernst Freundlich, the director of an iron foundry in Wiesbaden-Biebrich. He did his doctorate in 1910 in Göttingen under Felix Klein on a problem of analytical function theory and then became an assistant at the Berlin observatory , where he was entrusted with routine measurements.

In 1911 the young physicist at the Charles University in Prague , Albert Einstein , published a version of the later general theory of relativity : On the influence of gravity on the propagation of light (Ann. Phys. 35 (1911) 898). He predicted a deflection of light rays that tangentially graze the edge of the sun by only 0.85 arcseconds. (In the final version of 1915/6 the value increases to 1.75 by taking into account the curvature of space.) His colleague, the astronomer Leo Wenzel Pollak , was looking for astronomers who should observe this effect. All experienced astronomers saw no chance. Freundlich, who wanted to escape the stupid routine, enthusiastically accepted the challenge. This marked the beginning of a long collaboration with Einstein.

First he tried to determine the deflection of light rays in the gravitational field of the sun from old solar eclipse photo plates. This failed because the recordings were optimized for other destinations. But with the publication of the negative result in 1913, two years before the publication of the final version of the general theory of relativity, the ideas of the still relatively unknown professor at the Charles University in Prague became known to German astronomers. At the solar eclipse of August 21, 1914 in Russia, he wanted to provide experimental evidence. The expedition was specifically prepared and carried out from April 1914, but failed when the First World War broke out . Freundlich was interned in Russia. Even with further solar eclipse expeditions until 1954 no satisfactory results could be achieved, often the weather prevented that.

After returning to Germany, Freundlich was very committed to the construction of a solar observatory, which was built as the Einstein Tower in Potsdam . Freundlich, who played the cello, met her husband, the architect Erich Mendelsohn , who built the Einstein Tower through the cellist Luise Maas . Freundlich later headed the Einstein Institute belonging to the observatory, part of the Astrophysical Observatory (AIP). However, the effect of the redshift of spectral lines in the gravitational field of the sun, predicted by the general theory of relativity , could not be proven. In 1929 he led a solar eclipse expedition to Sumatra , where u. a. Walter Grotrian took part.

In 1933 Freundlich had to leave Germany because his father's Jewish grandmother made him fall under Section 3 of the "Professional Civil Servants Act" , the " Aryan Paragraph ." Until 1937 he headed the Astronomical Institute of Istanbul University , where he gave lectures, developed new textbooks in collaboration with Wolfgang Gleißberg and also set up a solar observatory. Until 1939 he held a chair at the Charles University in Prague .

Via Holland, on the recommendation of Arthur Stanley Eddington, he came to the University of St Andrews , where he set up an observatory. From 1951 to 1959 he held the John Napier Chair of Astronomy.

The measurements of the deflection of the light at the edge of the sun during solar eclipses had confirmed the general theory of relativity, but there was a problem: The measured value of the deflection was slightly higher than the theoretical value of 1.75. Freundlich tried throughout his life to determine the reason In doing so, he not only distanced himself further and further from the generally accepted theories, but also got further and further sidelined among his colleagues. For example, in 1953 he and Max Born proposed an alternative theory on the redshift of galaxies (Die Temperatur of the universe was calculated in the range 1.9 to 6 K.) Towards the end of his life radio astronomers then confirmed the theoretical value and in 1941 he was elected a member of the Royal Society of Edinburgh .

After his retirement he returned to Germany. He settled in his native Wiesbaden and taught as an honorary professor at the Johannes Gutenberg University in Mainz.

He is the namesake of the moon crater Freundlich .

family

In 1913 he married the Jewess Käte Hirschberg. The marriage remained childless and after the death of his wife's sister they adopted her children Hans and Renate.

Publications (selection)

  • Analytical functions with arbitrarily prescribed, infinitely-leafed areas of existence , dissertation, Göttingen, 1910
  • About an attempt to test the deflection of light in gravitational fields assumed by A. Einstein , Astronomische Nachrichten 193 (1913) 369
  • The basics of Einstein's theory of gravity . With a foreword by Albert Einstein, Berlin: Springer, 1916.
  • The tower telescope of the Einstein Foundation , Berlin: Julius Springer, 1927
  • with Harald v. Klüber and Albert von Brunn : Further investigations into the determination of the deflection of light in the gravitational field of the sun , Potsdam: [Astrophysik. Observatory, Einstein-Inst.], 1933. (Annals of the Bosscha-Sterrenwacht, Lembang (Java)).
  • Erwin Finlay-Freundlich: Cosmology (= International Encyclopedia of Unified Science . Volume 1, No. 8). University of Chicago Press, Chicago 1951; 3rd edition 1962.
  • Erwin Finlay-Freundlich: About the redshift of the spectral lines and Max Born: Theoretical remarks on Freundlich's formula for the stellar redshift - Göttingen: Vandenhoeck & Ruprecht, 1953, pp. 96-108 (Nachrichten der Akademie der Wissenschaften in Göttingen, born 1953, No. 7)

literature

  • Klaus Hentschel Erwin Finlay Freundlich and testing Einstein's theory of relativity , Archive History Exact Sciences, Volume 47, 1994, pp. 143-201
  • Klaus Hentschel: The Einstein Tower. Erwin F. Freundlich and the theory of relativity - approaches to a “dense description” of institutional, biographical and theoretical-historical aspects. Spectrum, Heidelberg 1992, ISBN 3-86025-025-6 .

See also

Web links

Individual evidence

  1. ^ Fellows Directory. Biographical Index: Former RSE Fellows 1783–2002. Royal Society of Edinburgh, accessed December 6, 2019 .
personal data
SURNAME Kind, Erwin
ALTERNATIVE NAMES Kindly, Erwin Finlay
BRIEF DESCRIPTION German astrophysicist , brother of Herbert Finlay Freundlich
DATE OF BIRTH May 29, 1885
PLACE OF BIRTH Biebrich
DATE OF DEATH July 24, 1964
Place of death Wiesbaden