American physicist, born in Strelno, Prussia (1852-1931). He is remembered for his work in optics, particularly for his early, extremely accurate experiments to determine the velocity of light. Michelson invented the interferometer, which he used to determine the effect of Earth's motion on the observed velocity of light. He was also interested in astronomy, and, using his interferometer, accurately measured the diameter of the star Betelgeuse. He was awarded a Nobel Prize in physics in 1907.