“The velocity of light is so enormously greater than with which we are accustomed to deal that the mind has some little difficulty in grasping it… we can, perhaps, give a better idea of this velocity by saying that light will travel around the world seven times between two ticks of a clock.” Albert A. Michelson in his “Light Waves and their Uses” (1903).
Albert A. Michelson is mostly known for his work on the measurement of the speed of light. Less well-known is his harmonic analyzer, an early analog computer.
Albert Abraham Michelson was born on December 19, 1852, in Strelno, Prussia, which today is called Strzelno in Poland. His father, Samuel Michelson, was a merchant of Jewish descent. Since there were frequent purges and progroms in those days, the family left for the United States when the young Michelson was two years old. They settled initially in Murphy’s Camp in Calaveras County, some 50 miles south-east of Sacramento, where Samuel sold his merchandise to the gold miners. Later they moved on to Virginia City, Nevada, but soon moved to San Francisco, where the young Michelson received his early schooling. In 1869 he graduated there from High School. By this time his father had managed to contact the local Congressman who would be appointing a candidate to the U.S. Naval Academy in Annapolis, but the position went to someone else. President Ulysses S. Grant would also appoint ten candidates and the Congressman wrote to the President on his behalf. Despite all ten scholarships already having been awarded, President Grant managed to find one extra scholarship for Michelson to study at the U.S. Naval Academy. Michelson graduated as an Ensign in 1873 with a first place in optics, but only 25th place in seamanship.
The speed of light
After a two-years’ cruise through the West-Indies, he became an instructor in physics and chemistry at the Naval Academy. While lecturing and demonstrating Foucault’s method for determining the speed of light, he suddenly realised that by redesigning the Foucault machine he could obtain a far greater accuracy. He managed to obtain a $2,000 loan from his father in law – he had married Margaret Hemingway in 1877 – which he needed to buy high-quality mirrors and lenses. He used a system whereby he shone a light on a rotating hexagonal mirror which reflected the light on another mirror 35 km away. It would then be reflected upon another side of the hexagonal mirror which could be achieved by rotating the mirrors at about 32,000 rpm. Using the distance travelled by the light and the rotation speed of the mirrors, it would be possible to calculate the speed of light. Michelson obtained a result that was far more accurate than Foucault’s and published his calculation for the speed of light in 1879 as 299,910±50 km/sec – remarkably accurate because today we know that the speed of light is 299,792.458 km/sec. The new findings were published by the New York Times and this made him instantly famous.
The results also came to the attention of astronomer Simon Newcomb who headed the Nautical Almanac Office in Washington. Newcomb managed to attract Michelson to the Nautical Almanac Office in 1879 and advised him to pursue a career in physics. In 1880 Michelson was granted leave of absence to study in Europe. He attended the Universities of Berlin and Heidelberg in Germany, and the College de France and the École Polytechnique in Paris, France, where he accurately measured the International Standard Meter.
While in Berlin he invented a new interferometer to determine the effect of the Earth’s motion on the observed velocity. The instrument also enabled him to measure distances with much greater accuracy, such as the distance from the Earth to the Moon (see the Gambia stamp above).
The Michelson-Morley experiment
In 1883 Michelson returned to the States, resigned from the Navy and accepted an appointment as Professor of Physics in the Case School of Applied Science, Cleveland, Ohio. In 1887 Michelson and Edward Morley carried out the Michelson-Morley experiment to research the expected motion of the Earth relative to the aether – the medium through which light was assumed to travel. Surprisingly, their findings came up with a null result. Michelson repeated the experiment in later years with greater accuracy but again with a null result. He found it difficult to accept that the concept of aether as a medium for the propagation of light was a fallacy.
In 1890 Michelson accepted a position as Professor of Physics at Clark University in Worcester, Massachusetts and two years later he was appointed Professor of Physics and the first Head of Department of the newly organized University of Chicago.
Michelson’s analog computer: the harmonic analyzer
Similarly to William Thomson (a.k.a. Lord Kelvin) who had built an harmonic analyzer which functioned as a tide predictor, Michelson also built harmonic analyzers to compute more precise calculations and measurements. His analog machines were used to calculate simple, regular waves which were combined to produce complex waves such as the light waves from a stellar body. In 1898, together with Samuel W. Stratton, Michelson designed a harmonic analyzer, having 80 components, to calculate light waves. This analog computing device could add up 20 terms of a mathematical formula called the Fourier series. Stratton would later become Director of the National Bureau of Standards and President of the Massachusetts Institute of Technology.
In 1907 Michelson was the first American to be awarded the Nobel Prize for Physics for “his optical precision instruments and the spectroscope and meteorological investigations carried out with their aid.”
During World War I Michelson rejoined the Navy. After the war he returned to the University of Chicago. In 1921 he managed to measure the diameter of the star Betelgeuse using an astronomical interferometer. He resigned and retired in 1929 and started work at the Mount Wilson Observatory in Pasadena, California. Here he continued with new and more accurate measurements of the speed of light.
Michelson died on May 9, 1931, in Pasadena, California, at the age of 78.
Michelson is shown on the left in both stamps
from the Nobel Prize for Physics, Michelson received many honorary degrees in law
and science from American and foreign universities as well as an impressive list
of awards, medals and similar honours:
1900 – President of the American Physical Society.
1904 – Received the Matteucci Medal of the Societá Italiana.
1907 – Received the Copley Medal of the Royal Society.
1910-1911 – President of the American Association for the Advancement of Science.
1912 – Received the Elliot Cresson Medal of the Franklin Institute.
1916 – Received the Henry Draper Medal of the National Academy of Sciences.
1923 – Received the Franklin Medal of the Franklin Institute.
1923 – Received the Gold Medal of the Royal Astronomical Society.
1923-1927 – President of the National Academy of Sciences.
1929 – Received the Duddell Medal of the Physical Society.
He also was Fellow of the Royal Astronomical Society, Fellow of the Royal Society of London, Fellow of the Optical Society and an Associate of l’Académie Française in Paris.
The Michelson Crater on the Moon has been named in his honour.
Michelson House at the University of Chicago is an undergraduate dormitory.
Michelson House at the Case Western Reserve University in Cleveland, Ohio, is an undergraduate residence hall.
Michelson Hall at the United States Naval Academy houses the departments of Computer Science and Chemistry.
The Naval Air Weapons Station China Lake in Ridgecrest, California, has a Michelson Laboratory.
The Computer Measurement Group awards since 1974 the A.A. Michelson Award for technical excellence and professional contributions.
Philatelically speaking, Michelson has been portrayed on a number of stamps, all of which are shown in this article.
© Wobbe Vegter, 2010