Used with
permission of Maiken Naylor, University at Buffalo, Buffalo, NY, USA,
http://ublib.buffalo.edu/libraries/units/sel/exhibits/stamps
Albert Michelson (1852-1931) was the first American to win a Nobel prize (physics, 1907) but has not been recognized for this achievement by the U.S. Postal Service. A Swedish stamp gives us his small profile. His studies of the velocity of light with ever greater accuracy were based on a modification of Foucault's rotating mirrors. Light, as a wave motion, was then supposed to require the presence of a medium for its propagation, and this invisible substance was called the luminiferous ether, through which the earth also moved. It was supposed that light would have different velocities when moving perpendicular and parallel to the hypothetical ether, being "dragged" in the former case. By an ingenious experiment of splitting light beams and bringing them back together in his interferometer, Michelson and his associate Edward Morley, a chemist dedicated to producing high precision instruments, were unable to detect any difference in time traveled for the split beams, both parallel to and with the ether. This failed experiment obviated the need for the ether's existence, and proved that the velocity of light is constant, an assumption later made by Einstein in his general theory of relativity.