Albert Abraham Michelson
Albert Abraham Michelson ( born December 19, 1852 in Strelno ( Posen ); † May 9, 1931 in Pasadena ( California)), was an American physicist of German origin. He was known for the eponymous Michelson interferometer. In 1907 he became the first American to win the Nobel Prize for Physics.
Life
Michelson was born in Strelno. His Jewish parents emigrated to the United States when he was two years old.
He began in 1869 to study at the U.S. Naval Academy in Annapolis in 1873 and reached a conclusion. From the beginning, Michelson was fascinated by the science.
Inspired by translations of works by Adolphe Ganot and its discussion of a universal ether, he was particularly interested in the problem to measure the speed of light. After two years studying in Europe, he retired from the Navy in 1881 from. In 1883 he accepted a position as professor of physics at the Case School of Applied Science in Cleveland (Ohio ) and focused on the development of an improved interferometer.
After he had worked from 1889 as a professor at Clark University in Worcester (Massachusetts), he was appointed in 1892 as professor and head of the physics department of the newly founded University of Chicago.
1907 Michelson became the first American who received the Nobel Prize in Physics ( "for his optical precision instruments and the spectroscopic and metrological investigations carried out "). In 1923 he was awarded the Gold Medal of the Royal Astronomical Society.
The speed of light
Early measurements
Already in 1877, while he was still an officer in the U.S. Navy, Michelson began planning for an improvement of the rotating mirror method for the measurement of the speed of light Léon Foucault. He wanted to use an improved appearance and a longer distance. In 1878 he made some preliminary measurements with very improvised equipment.
At this time his work aroused the attention of Simon Newcomb, Director of the Nautical Almanac Office, who had already made plans for their own investigations. Michelson published his result of 299 910 ± 50 km / s in 1879, before moving to Newcomb to Washington DC went to assist him in his measurements there. Thus, a long professional collaboration and friendship began between the two.
Newcomb received his project better financed a value of 299 860 ± 30 km / s, just within the errors consistent with Michelson's value.
Michelson improved its measurement method and published in 1883 a measurement of 299 853 ± 60 km / s, much closer to that of his mentor.
Mount Wilson and the time until 1926
In 1906 a new electrical method the National Bureau of Standards was used by EB Rosa and NE Dorsey, with whom she / s received a value for the speed of light 299 781 ± 10 km.
Although it turned out afterwards that the measurement was strongly influenced by the poor electrical standards this time, it seems to have set a trend for more lower readings in transition.
From 1920 Michelson started planning for a definitive measurement of the Mount Wilson Observatory with a baseline according to Lookout Mountain, a significant elevation on the south side of Mount San Antonio ( Old Baldy ), about 22 miles away.
1922 began, the U.S. Coast and Geodetic Survey with a two-year careful measurement of the base line with the straight has become available invar tapes. With the 1924 preserved length of the baseline measurements were made in the following two years, with whom / s was obtained, the published value of 299 796 ± 4 km.
It is equally well known as the measurement, that she was overwhelmed with problems, of which the haze produced by the smoke of the fires, which clouded the mirror image, was not the least. It is also likely that the heroic work of the U.S. Geological Survey Office, has been affected, with an estimated error of less than 1 ppm, by a shift of the baseline, which was caused by the Santa Barbara Earthquake on 29 June 1925 ( estimated thickness 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 that significantly exceeded all of Michelson's value of 1926.
Michelson was looking for a different method of measurement, but this time in an evacuated tube to avoid difficulties of image interpretation due to atmospheric effects. In 1930 he began a collaboration with Francis G. Pease and Fred Pearson to perform measurements in a 1.6 -km-long tube in Pasadena ( California). Michelson died after he had completed 36 of 233 measurement series. The experiment was significantly affected by geological instability and condensation problems before the result of 299 774 ± 11 km / s, published consistent with the previous optoelectronic values in 1935 after his death.
Interferometry
In 1881 he worked during a stay in Berlin and Potsdam in an experiment that has gone down as the Michelson - Morley experiment in the history of physics - repeated in an improved form, together with his colleague Edward Williams Morley 1887 in Cleveland. The movement of the earth should be determined relative to the ether, a hypothetical medium that you took as a carrier of light waves. Contrary to Michelson's firm conviction that there is a universal ether, but a movement of the earth could not be established in this way. Although it is unclear whether Albert Einstein knew this experiment, especially this experiment is regarded as one of the cornerstones of the theory of relativity.
In 1920, he conducted an experiment with a 6- m- beam interferometer. The bar with its mirror system was mounted in front of a 254 cm telescope. The light from a star was projected by movable mirror to the beam center, and from there into the telescope. In a telescope, a strip system can then be seen. If you push the mirror outward, eventually disappear the strip. The angular diameter of the star from the distance between the mirror then be calculated for a known distance and the diameter in kilometers. Michelson determined in this way the diameter of Betelgeuse to 386 million km.
Awards and honors
The Franklin Institute awarded him the honor of Albert A. Michelson Medal.
Michelson was a member of the Federation of the Freemasons.
Literature and Film
- Dorothy Michelson Livingston: The Master of Light. A biography of Albert A. Michelson. University of Chicago Press, Chicago IL et al 1979, ISBN 0-226-48711-3 (A phoenix book 813).
- The young Albert A. Michelson is the thematic main character in an episode of the western series Bonanza from 1962 The original English title is:. " Look to the Stars" No. S03E26. In Germany was the result: " Small People - Great People ".