Michelson, Albert A. 1852-1931

MICHELSON, ALBERT A. 1852-1931

Physicist

Nobel Prize Winner

The first American to win the Nobel Prize for physics, awarded in 1907, Albert Abraham Michelson is still renowned for his measurements of the speed of light and his calculation of the size of Betelgeuse, the first star other than the sun to be measured.

Background

Born to Jewish parents in a small Polish town that was at the time part of Prussia, Michelson immigrated to the United States with his family when he was four years old. He graduated from Annapolis in 1873 and served in the fleet until returning to the Naval Academy as an instructor in 1875. After study in Germany and France (1880-1882), he taught at Case School of Applied Science (1882-1889), Clark University (1889-1892), and the University of Chicago (1892-1931).

Early Work

In 1878-1879 Michelson measured the speed of light with impressive accuracy and found it to be a constant. He refined his measurements in 1882, coming up with 299,853 kilometers per second (a little over 186,000 miles per second), the accepted figure until 1927, when he was able to find an even more precise measurement. After moving on to Case in Cleveland, Michelson worked with Edward Morley on an experiment to prove the existence of the ether, the substance that was believed to fill outer space. Their failure to find ether eventually led scientists to abandon the ether theory and prepared the way for the conception of light rays as particles.

Star Size

While Michelson was at the University of Chicago he spent his summers at the California Institute of Technology and the nearby Mount Wilson Observatory. Using the 100-inch telescope, then the largest inthe world, he built an interferometer onto it so that he could measure the diameter of a star. He selected Betelgeuse, the largest star in the constellation Orion, and with only the light from the opposite edges of Betelgeuse shining through the slits in the interferometer, he was able to gauge the star's angular diameter. Already knowing the distance of the star from Earth, Michelson then used trigonometry to calculate the actual diameter of Betelgeuse as 386 million kilometers, or 240 million miles. The final calculations and the dramatic announcement that Michelson was the first man ever to measure the size of a star (other than the sun) were made in December 1920.

Sources:

Bernard Jaffe, Michelson and the Speed of Light (Garden City, N.Y.: Doubleday, 1960);

Dorothy Michelson Livingston, The Master of Light (New York: Scribners, 1973).