Overview

In 1887 Albert A. Michelson (1852-1931) and Edward W. Morley (1838-1923) performed what has become one of the most famous physics experiments in history. Using an extremely sensitive optical instrument—the interferometer—they attempted to measure Earth's velocity with respect to the luminiferous ether, a hypothetical substance that most nineteenth-century physicists believed necessary for the propagation of light. Against all expectations, their experiment yielded a negative result, indicating no motion of Earth relative to the ether. Ether theories were modified to account for this null-result, but no fully satisfactory solution presented itself until the introduction of Albert Einstein's special theory of relativity in 1905.

Background

The optical experiments of Thomas Young (1773-1829) and Augustin de Fresnel (1788-1827) at the beginning of the nineteenth century helped revived the wave theory of light. As with...