Albert A. Michelson:

CAREER AND INFLUENCE

Albert A. Michelson is renowned for his experiments and precise determinations of the velocity of light, ether drift, length of the standard meter, spectral lines, diameters of stars, and rigidity of the earth. Additionally, Michelson invented different types of instruments to help carry out these experiments. He is best known for his invention of the interferometer, the harmonic analyzer (with S.W. Stratton), the echelon spectroscope, and ruling engines. Michelson accomplished his research and inventions in the course of his teaching career as a professor of physics at various institutions of higher education.

Michelson began his teaching career in December 1875, as an instructor of physics and chemistry at the Naval Academy. He left the Academy in 1879 to aid Simon Newcomb in his experiments with the velocity of light at the Nautical Almanac Office. From 1880 to 1882, Michelson pursued graduate studies in Berlin, Heidelberg, and Paris, followed by seven years as an instructor in physics at the then newly established Case School of Applied Science, from 1882-1889. He then moved to Worcester, Massachusetts to become the first Chair of Physics at Clark University from 1889-1892.

Michelson's longest and most significant teaching tenure, however, was as Professor and first Head of the Department of Physics at the University of Chicago, from 1892-1930. He was one of the first physicists to occupy the Ryerson Physical Laboratory, which would eventually employ a number of Nobel Laureates and later become known as the home of the "Manhattan Project." Albert A. Michelson officially retired from teaching in 1930, having received the first "Distinguished Service Professor" award by the University in 1925. Earlier in his career, Michelson had also been an exchange professor in Germany and France.

It was during his days as an instructor at the Naval Academy that Michelson conducted his first velocity of light experiments as a part of a class demonstration in 1877. He made an important modification of Foucault's earlier method for determining the velocity of light. He contributed ten dollars of his own money for a revolving mirror, which enabled him to complete the experiment successfully. Michelson's determination in 1882 at Case of the velocity of light, 299, 853 +/- 60 (km/sec), became the standard measurement until his more accurate result of 299,796 +/- 4 (km/sec) at Mount Wilson in 1926. The latter is still considered the most accurate result using optical techniques.

In 1929, at Irvine Ranch in California, Michelson began his last attempt to determine the most exact measurement of the velocity of light in a vacuum tube. The final results of this experiment were determined in 1933, two years after Michelson's death, by his long-time associate Fred Pearson and astronomer F. G. Pease. The velocity calculation of 299,774+/- 11 (km/sec) was the least accurate of all of Michelson's attempts. The current accepted measurement of the velocity of light, or of the constant "c", is about 300,000 km/sec or 186,000 miles/sec.

Some of Michelson's other significant discoveries include the length of the standard meter (used as the standard length from 1893-1960), the rigidity and elasticity of the earth in 1919, and in 1920 the first measurement of the angular diameter of a star (the star named "Betelgeuse" of the constellation Orion). He also studied the metallic colors in birds and insects. In addition to his research and teaching, over seventy-five of Michelson's articles and lectures were published, along with three of his books: Determination Experimentale de la Valuer du Metre en Longueurs d'Ondes Lumineuses (1894), Light Waves and Their Uses (1903) and Studies in Optics (1927). Michelson's report conveying the results of his experiment at the U. S. Naval Academy in 1879, "Experimental Determination of the Velocity of Light", was also later published in 1880.

Throughout his career, Michelson taught and inspired people who would themselves become successful teachers, physicists, and inventors. His most indelible sphere of influence existed at the University of Chicago. Notable scientists, such as S.W. Stratton and George Ellery Hale, had collaborated with Michelson on various projects while making a name for themselves in their respective fields. Stratton, who later became Director of the National Bureau of Standards and President of the Massachusetts Institute of Technology, helped Michelson with teaching as well as with the invention and development of the Michelson-Stratton harmonic analyzer. Hale, who became a famous astrophysicist noted for his discoveries about the surface of the sun, was a colleague of Michelson's in the Physics Department; while at the University of Chicago he organized the Yerkes Observatory and from 1904-1923 also organized and directed the Mount Wilson Observatory. Robert A. Millikan, a Michelson student and later one of his faculty members, became the second American to win the Novel Prize in Physics in 1923. He was well known for his research of electricity, optics, and molecular physics. Arthur Holly Compton, also a faculty member in Michelson's department at Chicago, became the third American physicist to win the Nobel Prize in Physics in 1927. He was recognized for his work on cosmic rays, atomic energy, and the Compton effect.

First page from a reproduction of Michelson's report on his "Experimental Determination of the Velocity of Light" conducted at the U. S. Naval Academy. He submitted this report to the Secretary of the Navy via letter on September 29, 1879. [488K]

Ryerson Laboratory staff at the University of Chicago, 1926. Michelson was one of the first occupants of Ryerson Physical Laboratory in 1892, when he began working at he University of Chicago as a professor of Physics and the first Head of the Department. [951K]

Lecture notes from one of Michelson’s notebooks, n.d. [506K]

Schematic diagram of the Michelson interferometer, n.d. [1052K]

Michelson using a spectrograph to test a diffraction grating, Ryerson Physical Laboratory, University of Chicago, circa 1920. [646K]

Michelson invented different types of interferometers, such as the small interferometer and the vertical interferometer, in addition to the well known traditional Michelson interferometer. The angular interferometer is shown here, n.d. [637K]

Michelson’s colleagues and assistants at the velocity of light experiment site in Clearing, Illinois, in the winter of 1924. [1109K]

The Michelson-Stratton harmonic analyzer, one of the first mechanical analogue computers, recorded data from spectroscopic experiments, n.d. [795K]