Born Aug. 22, 1834, in Roxbury, Mass.; died Feb. 27, 1906, in Aiken, S.C. American astrophysicist.
Langley was appointed director of the Allegheny Observatory in 1867. Beginning in 1887 he was at the Smithsonian Institution in Washington. Langley studied the distribution of energy in the solar spectrum and reestablished the solar constant. He invented the bolometer in 1880–81 and used it to measure the intensity of solar radiation. On the basis of these measurements, Langley compiled an atlas in 1901 of the infrared part of the solar spectrum.