Langley, Samuel Pierpont (1834-1906), a United States astronomer, physicist, and aviation pioneer. In 1896 Langley's 26-pound (12-kg) unmanned model airplane flew for 90 seconds, traveling about half a mile (800 m). In 1903 he twice failed in attempts to fly a full-sized manned airplane---and nine days after his last effort the Wright Brothers successfully ushered in the age of powered, heavier-than-air flight. Langley's flying machine was later rebuilt with modifications and flown, and is now the property of the Smithsonian Institution, Washington, D.C.

Langley was born in Roxbury, Massachusetts. He never attended college, but educated himself while practicing engineering and architecture. In 1867 he joined the faculty of the Western University of Pennsylvania (now the University of Pittsburgh) as professor of astronomy and physics and director of the Allegheny Observatory. From 1887 to his death, Langley was secretary of the Smithsonian Institution.

The bolometer, an instrument that measures heat radiation, was invented by Langley in 1878. He used the bolometer in trying to determine how much radiation the earth receives from the sun when atmospheric absorption is disregarded.

The Langley Medal, established by the Smithsonian Institution in 1909 in commemoration of Langley's experiments, is awarded to individuals for distinguished achievement in the science of aviation and space flight.