In 1878 he constructed a rotating-mirror apparatus for measuring the velocity of light, on which he collaborated with S. Newcomb. The interferometer he built for the Michelson–Morley experiment of the 1880s led him to construct highly accurate spectroscopes and diffraction gratings for astronomy, and also the Michelson interferometer. In 1920, Francis Gladheim Pease (1881–1938) measured the angular diameter of Betelgeuse with the stellar interferometer that Michelson built and installed on the 100-inch (2.5-m) telescope at Mount Wilson Observatory. For the instruments he made and the measurements made with them, Michelson received the 1907 Nobel Prize in Physics.