A bolometer (Greek: βολόμετρον "bolometron", meaning measurer (-μετρον) of thrown things (βολο-) ) is a device for measuring the power of incident electromagnetic radiation via the heating of a material with a temperature-dependent electrical resistance. It was invented in 1878 by the American astronomer Samuel Pierpont Langley. The name comes from the Greek word bole (βολή), for something thrown, as with a ray of light.[1]