Albert Abraham Michelson
1852-1931
American Physicist
Albert Michelson was a renowned physicist whose work in optics inspired, among others, Albert Einstein (1879-1955). He made the first accurate determinations of the speed of light and helped to disprove the existence of "ether," previously thought to permeate all space.
Michelson was born in Strzelno, Poland, to Samuel and Rozalia Michelson. The Michelson family left Poland for the United States when Albert was three, his father eventually becoming a successful merchant in San Francisco. Michelson entered the U.S. Naval Academy at age 17, where he performed well in his academic studies but rather poorly in seamanship. He graduated in 1873 and was a science instructor at the Academy until 1879.
In 1878 Michelson began what was to be his life's passion—obtaining accurate measurements of the speed of light. He first used crude homemade equipment to arrive at reasonable values. Knowing he would need to study optics in order to obtain the accuracy he desired, Michelson spent two years in Paris, Berlin, and Heidelberg. During this period, he resigned from the Navy to be able to concentrate on his research. Upon returning to the United States in 1882, he calculated that the speed of light was 299,853 km/sec, the most accurate measurement to be made until his own revision nearly 30 years later.
Accepting a professorship in physics at Case University in Cleveland, Ohio, Michelson began a collaboration with Edward Morley (1838-1923) to try to prove or disprove the existence of "ether," a substance that was thought to permeate space, allowing electromagnetic radiation to be transmitted. The Michelson-Morley experiment was elegant and decisive, using the wave-like properties of light in a device called an interferometer.
When light waves meet and are slightly out of phase (meaning the crests and troughs do not match each other exactly), observers see a series of bright and dark bands. The bright bands represent places where two crests meet and reinforce each other, while the dark bands show where a crest and a trough meet and cancel each other out. Someone holding two fingers very close together in front of a light can see these dark and light bands between their fingers if they look closely and carefully.
Michelson and Morley realized that as the Earth moved in its orbit it would be in motion across the ether. That meant that, if the ether existed, a light shining in different directions would be moving with different velocities with respect to the ether. They set up an "L"-shaped set of mirrors and bounced beams of light from a single source from the mirrors at either end of the "L." As the light returned to the origin, they looked for bands, because differences in the travel times of the beams of light would cause the beams to be out of synch with each other. When repeated experiments showed no bands, Michelson and Morley reluctantly came to the conclusion that "ether" did not exist. This conclusion not only rattled conventional science, but also set the stage for the later theory of relativity. For this experiment and his groundbreaking work on the speed of light, Michelson was awarded the Nobel Prize in Physics in 1907, the first American to receive this honor. It is important to note that from the perspective of Michelsonand Morley this experiment was a failure, as they were attempting to show that ether existed. However, from their "failure" came a number of advances in our understanding of the physical universe, proving in the end more profitable than most experimental "successes."
Of Michelson's work, Einstein said: "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."
Michelson commented 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 decimals." The irony of this quote is that Michelson's own work set the stage for discoveries in relativity that would overturn our view of the universe. Also of interest, this statement was made shortly before the discoveries of x-rays and radioactivity, which led to studies of the atom, quantum physics, and other areas that are still being fruitfully explored today.
In addition to his scientific accolades, Michelson served as the first chair of the Physics Department at the University of Chicago and was president of the National Academy of Sciences from 1923-1927. He married twice during his life, having three children in each marriage, and died in 1931 at the age of 78.
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