Albert Abraham Michelson (19.12.1852—9.05.1931) was an American physicist, a member of the National Academy of Sciences (1888) and its president in 1923-27. He was born in Strelno (Poland). In 1854 he moved to the USA, where he graduated from the Naval Academy (1873), and in 1875 — 79 he worked at the Naval Academy. In 1880 — 82 he furthered his knowledge in Germany and France. In 1883-89 he was professor at the School of Applied Science in Cleveland, in 1889 —92 at Clark University in Worcester and in 1892—29 at the University of Chicago.
His main work was in the field of optics and spectroscopy. He invented the interferometer (the Michelson interferometer), which played a considerable part in the substantiation of special relativity and in the study of spectral lines. He carried out a series of experiments on the precise determination of the speed of light (1878-82 and 1924-26), obtaining the value 299 796 +- 4 km/s, and on the determination of the relative motion of the Earth and the ether (1881, 1886-87, 1929). The purpose of the latter experiments was to detect experimentally the motion of the Earth relative to the stationary ether, in other words to detect the so-called ether wind. As is well known, these experiments of Michelson's (with Morley) in 1887 gave a negative result, and it was this that did much to bring about the acceptance of special relativity. In 1892—93 he carried out an experiment comparing the length of the standard metre with the length of a light wave (the red spectral line of cadmium). He carried out research on the fine structure of spectral lines, which he discovered (1891), proved the rotation of the Earth about its axis by an optical method and determined (1925) the speed of rotation, and in 1907 designed a spectral instrument of high resolving power (the Michelson echelon), as well as perfected diffraction gratings and a range-finder. For the precision instruments he created and for the spectroscopic and metrological research carried out with them Michelson was awarded the Nobel Prize in 1907.
In 1890 he put forward the idea that interference effects could be used in astronomy, and he designed a stellar interferometer for measuring the angular sizes of stars. In 1920, with F. Pease, he used this interferometer to measure for the first time the diameter of the giant star Betelgeuse.
A foreign member of the USSR Academy of Sciences (1926). In 1901— 03 he was president of the American Physical Society. The Copley Medal (1907).