US astronomer, scientist, and inventor of the bolometer, an instrument that measures radiation. His steam-driven aeroplane flew for 90 seconds in 1896 - the first flight by an engine-equipped aircraft.
He was professor of physics and astronomy at the Western University of Pennsylvania 1866-87, and studied the infrared portions of the solar system.
From 1887 he was secretary of the Smithsonian Institution in Washington DC. He founded the Smithsonian Astrophysical Observatory in 1890 and turned to pioneering work in aerodynamics, contributing greatly to the design of early aircraft. He built and tested the first successful (but uncrewed) heavier-than-air craft (aeroplane), which he launched by catapult and which flew over the Potomac River in 1896. The subsequent catapult-launched flights of the Wright brothers at Kitty Hawk owed much to Langley's principles as well as to the more powerful engines available by the early 1900s. The Langley design was tested in later years by using a model with a modern engine; it flew successfully with a pilot aboard.