Albert Abraham Michelson

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Portrait around 1900

Albert Abraham Michelson (born December 19, 1852 in Strelno , Posen Province , † May 9, 1931 in Pasadena , California) was an American physicist of German origin. He became famous for the Michelson interferometer named after him . In 1907 he was the first American to receive the Nobel Prize in Physics .

Life

Michelson was born in Strelno . His Jewish parents immigrated to the United States when he was two years old. They first settled in Virginia City and then moved to San Francisco .

Albert A. Michelson

Michelson began studying at the United States Naval Academy in 1869, graduating in 1873. Science fascinated him from the start.

Inspired by translations of the works of Adolphe Ganot and his explanations about a universal ether , he was particularly interested in the problem of measuring the speed of light . After studying in Europe for two years, he left the Navy in 1881. In 1883 he took a position as professor of physics at the Case School of Applied Science in Cleveland and focused on developing an improved interferometer .

After working as a professor at Clark University in Worcester ( Massachusetts ) from 1889 , he was appointed professor and head of the physics department of the newly founded University of Chicago in 1892 , where he worked with Edna Carter and Robert Andrews Millikan around 1888/89 .

In 1891 Michelson acquired a first patent for an optical range finder for the United States Navy . During the First World War he further developed his range finder from March 1917, and in the summer of 1918 George Ellery Hale announced the start of production of the first 50 devices of the new type in his workshop at the Mount Wilson Observatory .

In 1907 Michelson became the first American to receive the Nobel Prize in Physics ("for his optical precision instruments and the spectroscopic and metrological investigations carried out with them"). In 1923 he was awarded the gold medal of the Royal Astronomical Society .

The speed of light

Early measurements

As early as 1877, while he was still an officer in the US Navy , Michelson began planning an improvement in Léon Foucault's rotating mirror method for measuring the speed of light . He wanted to use improved optics and a longer route. In 1878 he made some preliminary measurements with heavily improvised equipment.

At the time, his work caught the attention of Simon Newcomb , director of the Nautical Almanac Office, who had already made plans for his own research. Michelson published his result of 299,910 ± 50 km / s in 1879 before he went to Newcomb in Washington DC to help him with his measurements there. Thus began a long professional cooperation and friendship between the two.

Newcomb received a value of 299,860 ± 30 km / s with his better financed project, which corresponds to Michelson's value within the measuring inaccuracy.

Michelson improved his measurement method further and in 1883 published a measurement of 299,853 ± 60 km / s much closer to that of his mentor.

Mount Wilson and the period up to 1926

In 1906 EB Rosa and NE Dorsey used a new electrical method from the National Bureau of Standards, with which they obtained a value for the speed of light of 299,781 ± 10 km / s.

Although it subsequently turned out that the measurement had been strongly influenced by the poor electrical standards of the time, it seems to have started a trend for rather lower measurement values.

From 1920, Michelson began planning a definitive measurement at the Mount Wilson Observatory with a baseline to Lookout Mountain, a significant elevation on the south side of Mount San Antonio (Old Baldy), about 22 miles away.

In 1922, the US Coastal and Geodesy Inspectorate began a two-year meticulous survey of the baseline using the newly available Invar tapes. With the length of the baseline obtained in 1924, measurements were made in the following two years, with which the published value of 299,796 ± 4 km / s was obtained.

As well known as the measurement is that it was inundated with problems , not the least of which was the haze created by the smoke from the forest fires that clouded the reflection. It is also probable that the heroic work of the US Geological Survey Authority, with an estimated error of less than 1 ppm , was affected by a shift in the base line by Santa Barbara - earthquake caused on June 29, 1925 (estimated magnitude 6 , 3 on the Richter scale ).

Michelson, Pease and Pearson 1932

The period after 1927 marked the beginning of new measurements of the speed of light with new optoelectronic sensors , all of which were significantly below Michelson's 1926 value.

Michelson looked for a different measuring method, but this time in an evacuated tube in order to avoid difficulties in interpreting images due to atmospheric effects. In 1930 he began working with Francis G. Pease and Fred Pearson to take measurements in a 1.6 km long tube in Pasadena . Michelson died after completing 36 of 233 series of measurements. The experiment was significantly affected by geological instabilities and condensation problems before the result of 299,774 ± 11 km / s, consistent with the previous optoelectronic values, was published in 1935 after his death.

Interferometry

In 1881, during a stay in Berlin and Potsdam, he worked on an experiment that went down in the history of physics as the Michelson-Morley experiment - repeated in an improved form together with his colleague Edward W. Morley in Cleveland in 1887. The aim was to determine the movement of the earth relative to the ether , a hypothetical medium that was assumed to be the carrier of light waves. Contrary to Michelson's firm belief that there is a universal ether, a movement of the earth could not be determined in this way. Although it is unclear whether Albert Einstein knew about this experiment, this experiment in particular is considered to be one of the cornerstones of the theory of relativity .

With their interferometer, Michelson and Morley were able to carry out precise measurements of the fine structure splitting in atomic spectra for the first time , which was theoretically explained by Arnold Sommerfeld in 1916 and is still the subject of current research with the introduction of the fine structure constants .

In 1920 he carried out an experiment with a 6 m bar interferometer. The beam with its mirror system was mounted in front of a 254 cm telescope. The light from a star was projected to the center of the bar and from there into the telescope through a sliding mirror. A system of stripes can then be seen in the telescope. If you slide the deflecting mirror outwards, the stripes will eventually disappear. The angular diameter of the star can then be calculated from the distance between the deflection mirrors, and if the distance is known, its diameter in kilometers. In this way Michelson determined the diameter of Betelgeuse to be 386 million km.

Awards and honors

The Franklin Institute awarded him the Albert A. Michelson Medal in his honor .

Michelson was a member of the Freemasons Association .

Literature and film

  • Dorothy Michelson Livingston: The Master of Light. A biography of Albert A. Michelson (= A phoenix book. 813). University of Chicago Press, Chicago IL a. a. 1979, ISBN 0-226-48711-3
  • The youthful Albert A. Michelson is the main themed character in an episode of the western series Bonanza from 1962. The English original title is: Look to the Stars No. S03E26. In Germany the result was: small people - big people .

Web links

Commons : Albert A. Michelson  - Collection of Images, Videos and Audio Files
Wikisource: Albert A. Michelson  - Sources and full texts

Individual evidence

  1. ^ Leonard Mlodinow : The window to the universe. A little history of geometry. Campus-Verlag, Frankfurt / New York 2002, ISBN 3-593-36931-1 , p. 171 (Part 4: The story of Einstein )
  2. ↑ Edna Carter . In: Physics Today , 16, 8 (1963), p. 74, at: scitation.org
  3. ↑ Misha Shifman: Standing Together In Troubled Times: Unpublished Letters Of Pauli, Einstein, Franck And Others. World Scientific, Hackensack (New Jersey) 2017, ISBN 978-981-3201-00-2 , p. 38.
  4. ↑ Johannes-Geert Hagmann: How physics made itself heard - American physicists engaged in “practical” research during the First World War . In: Physik Journal 14 (2015) No. 11, pp. 43–46.
  5. ^ AA Michelson, EW Morley: American Journal of Science. Vol. 34, 427 (1887); Phil Mag. 24, 463 (1887).
  6. ↑ John D. Barrow : Varying Constants. Phil. Trans. Roy. Soc. Lond. A363 (2005) 2139-2153, online
  7. ^ Members of the American Academy. Listed by election year, 1850–1899 ( PDF ). Retrieved September 24, 2015
  8. ↑ Member History: Albert A. Michelson. American Philosophical Society, accessed October 30, 2018 .
  9. ^ List of members since 1666: Letter M. Académie des sciences, accessed on January 23, 2020 (French).
  10. ^ Fellows Directory. Biographical Index: Former RSE Fellows 1783–2002. (PDF file) Royal Society of Edinburgh, accessed March 21, 2020 .
  11. ^ Foreign members of the Russian Academy of Sciences since 1724. Albert Abraham Michelson. Russian Academy of Sciences, accessed October 3, 2015 (Russian).
  12. ^ Wisdom Lodge List of Famous Freemasons . Wisdom Lodge # 202 Pasadena, CA. Archived from the original on January 28, 2013. Retrieved December 5, 2019.
personal data
SURNAME Michelson, Albert Abraham
ALTERNATIVE NAMES Michelson, Albert A.
BRIEF DESCRIPTION American physicist and Nobel Prize winner
DATE OF BIRTH December 19, 1852
PLACE OF BIRTH Strelno ( Poznan )
DATE OF DEATH May 9, 1931
Place of death Pasadena, California