Albert A. Michelson
Albert Abraham Michelson was born in Strzelno (Poland) on December 19, 1852. Son of Samuel Michelson and Rozalia, daughter of Abraham Przylubski from Inowroclaw. He left Poland with his parents in 1855. From New York, the family made its way to Virginia City, Nevada, and San Francisco, where the elder Michelson prospered as a merchant. At 17, Michelson entered the United States Naval Academy at Annapolis, Maryland, where he did well in science but was rather below average in seamanship. He was graduated in 1873, then served as science instructor at the academy from 1875 until 1879. In 1883 he accepted a position as professor of physics at the Case School of Applied Science in Cleveland. In 1892 Michelson, after serving as professor of physics at Clark University at Worcester, Massachusetts, from 1889, was appointed professor and the first head of the department of physics at the newly organized University of Chicago, a position he held until his retirement in 1929. From 1923 to 1927 he served as president of the National Academy of Sciences.
Albert A. Michelson
became the first American
to receive a Nobel Prize in physics, 1907.
In 1878 Michelson began work on what was to be the passion of his life, the accurate measurement of the speed of light. He was able to get useful values with homemade apparatus. Feeling the need to study optics before he could be qualified to make real progress, he travelled to Europe in 1880 and spent two years in Berlin, Heidelberg, and Paris, resigning from the navy in 1881. Upon his return to the United States, he determined the velocity of light to be 299,853 km s-1, a value that remained the best for a generation. When it was bettered, Michelson bettered it. Albert Michelson, the first chair of Physics Department at Clark University at Worcester, was the first to accurately measure the speed of light. Albert A. Michelson was the first Nobel laureate of the University of Chicago for his measurements of the speed of light.
Albert Michelson married Margaret McLean Heminway in New Rochelle, New York, on April 10, 1877. They had three children before they divorced: Albert Hemingway, Truman and Elsa.
After that Michelson was married to Edna Stanton. They had three children also: Beatice, Madeline and Dorothy.
Find more in Michelson's Genealogy Homepage
A.A.Michelson was a Mason.
It was at Clark University that Michelson conducted fundamental research leading to the determination of an international standard of measurement, the meter, in terms of a natural constant, the wave length of cadmium light. His numerous contributions to the physics of light included the invention of optical precision instruments, many of which he used in experiments that marked the beginning of modern physics.
The idea that interferometry might be applied to measure the size of stars was first proposed by a French astronomer, Armand Fizeau, in 1868. But the first real achievement of interferometry was a trailblazing series of experiments by Dr. Albert A. Michelson that began in April 1887. Michelson devised a system using mirrors and semitransparent mirrors (now known as beam splitters) for merging separated beams of light coming from the same object. The optical elements in the system were arranged in such a way that the beams "interfered" with each other; that is, the directions and distances of their light paths were so closely meshed that the beams could interact.
While in Europe, Michelson began constructing an interferometer, a device designed to split a beam of light in two, send the parts along perpendicular paths, then bring them back together. If the light waves had, in the interim, fallen out of step, interfererence fringes of alternating light and dark bands would be obtained. From the width and number of those fringes, unprecedently delicate measurements could be made, comparing the velocity of light rays travelling at right angles to each other.
It was Michelson's intention to use the interferometer to measure the Earth's velocity against the "ether" that was then thought to make up the basic substratum of the universe. If the Earth were travelling through the light-conducting ether, then the speed of the light travelling in the same direction would be expected to be equal to the velocity of light plus the velocity of the Earth, whereas the speed of light travelling at right angles to the Earth's path would be expected to travel only at the velocity of light. His earliest experiments in Berlin showed no interference fringes, however, which seemed to signify that there was no difference in the speed of the light rays, and, therefore, no Earth motion relative to the ether.
In Cleveland he concentrated his efforts on improving the delicacy of his interferometer experiment. By 1887, with the help of his colleague, American chemist Edward Williams Morley, he was ready to announce the results of what has since come to be called the Michelson-Morley experiment. Those results were still negative; there were no interference fringes and apparently no motion of the Earth relative to the ether.
It was perhaps the most significant negative experiment in the history of science. In terms of classical Newtonian physics, the results were paradoxical. Evidently, the speed of light plus any other added velocity was still equal only to the speed of light. To explain the result of the Michelson-Morley experiment, physics had to be recast on a new and more refined foundation, something that resulted, eventually, in Albert Einstein's formulation of the theory of relativity in 1905.
Michelson and his colleague, Dr. Edward W. Morley, used interferometry in a long and futile attempt to detect the existence of "ether," a kind of all-pervasive fluid that many scientists believed extended throughout the universe, providing a medium through which light waves could propagate. The Michelson and Morley experiment consisted of an L-shaped apparatus in which a beam of light was split in two, with the separated beams guided along perpendicular paths of identical length and then recombined. The scientists reasoned that if Earth was moving through a universal ocean of ether, the time needed by the two parts of the split light beam to traverse a sample of the ether current from perpendicular directions should differ slightly and that the difference should be detectable in the resulting pattern of interference fringes. But Michelson never found any difference. This historic null result, as scientists call it, was proof that ether, as it was then imagined, does not exist and that Einstein's special theory of relativity, which offers an alternative explanation for the propagation of light, is correct.
In 1878 Albert A. Michelson first accurately measures the speed of light with $10 worth of apparatus along the seawall.
Mt. San Antonio
Click here for zoomed view towards Mt. San Antonio on a clear day
"One of the most important scientific experiments of the 1920s took place on Lookout Mountain, a 6,812-foot high point on the south ridge of Mount Baldy. [Lookout Mtn. is a spur of Mount Baldy also known as Mount San Antonio; Mt. San Antonio is the highest mountain (10,064') in the San Gabriel Range - ed.]. This was the experiment by Albert A. Michelson [...] to determine the speed of light. In 1922, Dr. Michelson set up a rotating octagonal prism on Mount Wilson, called Station Michelson. On Lookout Mountain, 22 miles [35.5 km - ed.] away, he installed a concave mirror two feet in diameter, called Station Antonio. He then shot a beam of light [from] Station Michelson to the mirror at Station Antonio; the light beam was reflected back to Mount Wilson and the precise time measured. To insure the absolute accuracy of the experiment, it was vital to know the exact distance between the two stations. The distance was measured by the U.S. Coast and Geodetic Survey by triangulation from a 40-kilometer surveyed base line in the valley to the south. To quote William Bowie of the U.S.C.G.S., It is believed that the length of this line has been determined with greater accuracy than that of any line of triangulation in this or any other country. The possible error in the 22-mile distance between Mt. Wilson and Lookout Mountain was less than one-fourth of an inch! [...] Today, three inline concrete piers, the tallest one 42 inches high with a metal tablet marked Antonio 1922, stand alone amid the brush on Lookout Mountain."acc.: Robinson, J.W., 1991. The San Gabriels.
Big Santa Anita Historical Society,
Click on image to enlargement Courtesy of M.J.Keenan Courtesy of NOAA Photo Library Courtesy of M.J.Keenan The structures that sheltered the mirror on the Lookout Mountain site when the measurements were being taken Measuring the Pasadena Base Measured at accuracy of at least 1 part in 5 million Measured accurately to help Albert Michelson determine velocity of light Base line party of Clement L. Garner Measuring through house on Pasadena Base Line selected to pass through window and out other side Base line length was over 20 miles Base line party of Clement L. Garner Two recent photos of the Lookout Mt. site. The left one is without the shelters and in the right one Micheal John Keenan is standing next to and holding a hiking pole where the bolt is that held the mirror use to relect light back to Mt Wison. In the foreground is the survey marker pier that denotes the point of distance used to record repeated measurements of light sent from Mt Wilson.
In 1923 Michelson returned to San Gabriel Range and to the problem of the accurate measurement of the velocity of light. He made use of a special eight-sided revolving mirror (rotating octagonal prism) and obtained a value of 299,798 km s-1 for the velocity of light. To refine matters further, he made use of a long, evacuated tube through which a light beam was reflected back and forth until it had travelled 16 km through a vacuum. Michelson died before the results of his final tests could be evaluated, but in 1933 the final figure was announced as 299,774 km s-1, a value less than 2 km s-1 higher than the value accepted in the 1970s.
Albert Michelson advocated using some particular wavelength of light as a standard of distance (a suggestion generally accepted in 1960) and, in 1893, measured the standard metre in terms of the red light emitted by heated cadmium. His interferometer made it possible for him to determine the width of heavenly objects by matching the light rays from the two sides and noting the interference fringes that resulted. In 1920, using a 6-metre interferometer attached to a 254-centimetre telescope, he succeeded in measuring the diameter of the star Betelgeuse (Alpha Orionis) as 386,160,000 km (300 times the diameter of the Sun). This was the first substantially accurate determination of the size of a star.
Albert A. Michelson died on May 9, 1931 in Pasadena, California, (U.S.). Albert Einstein, in the same year, publicly paid tribute to Michelson's extensive contributions to science: "My honored Dr. Michelson, it was you who led the physicists into new paths, and through your marvelous experimental work paved the way for the development of the theory of relativity." Quotation from Michelson's address at the dedication ceremony for the Ryerson Physical Laboratory at the University of Chicago in 1894:
"The more important fundamental laws and facts of physical science have all been discovered, and these are now so firmly established that the possibility of their ever being supplanted in consequence of new discoveries is exceedingly remote.... Our future discoveries must be looked for in the sixth place of decimals."
THE MASTER OF LIGHTExamine the life and scientific career of Albert A. Michelson, a pioneer in the world of physics. His experiments triggered a progressive chain of advances in physics which helped to unravel and unify often opposing theories. It began with the properties of light, destroyed the theory of the luminiferous ether, and laid the groundwork for Einstein's Theory of Relativity as well as contemporary exploration of outer space and atomic energy. In besides its historical and scientific perspective, the film looks at the personal side of Michelson's life.
1984, Cinema Guild VHS, color, 25 mins., 16mm film/video
Directed by Steve Michelson
Read more in book of his daughter Dorothy Michelson Livingston (1973): Master of Light: A Biography of Albert A. Michelson. Scribner, New York (376 pp.) or in book of Bernard Jaffe, (1960): Michelson and the Speed of Light. Garden City, N.Y., Doubleday (197 pp.).
Albert A. Michelson, Albert Einstein and Robert A. Millikan at the Califonia Institute of Technology in 1931
Every year, a distinguished scientist is invited to come to the U.S. Naval Academy to present the Michelson Lecture.
Different portraits of Albert Abraham Michelson:
- A. A. Michelson as a Cadet at the Naval Academy
- A. A. Michelson in 1887
- A. A. Michelson in 1900
- A. A. Michelson Called Back to Active Duty (WWI)
- A. A. Michelson in 1910
- A. A. Michelson in 1928
- Side-View of Michelson's First Interferometer (1881)
- Top-View of Michelson's First Interferometer (1881)
- The Michelson-Morley Interferometer (1887)
- Illustrastion of Light Paths in the 1887 Interferometer
- Michelson-Gale Experiment at Clearing Illinois (1925)
- A Scale Model of Michelson's Massive Invar Interferometer (1926-27)
- Diagram of the Michelson-Pease-Pearson Interferometer (1929)
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Last Updated: 21 October 2007