DOPPLER, CHRISTIAN JOHANN Aus trian physicist, was born at Salzburg, on Novi 29, 1803. He was educated at Salzburg and Vienna, and became, in 185o, director of the Physical Institute and professor of experimental physics at Vienna. He died at Venice on March 17, 1853. Doppler's earliest writings were on mathematics, but his name is associated with his work in physics. In 1842 he published a paper "fiber das farbige Licht der Doppelsterne," which contained what is now known as Doppler's principle (see LIGHT, Waves and Interference). He drew the analogy between the sound coming from a moving source and the light coming from a moving star; as the pitch of sound from a moving source varies, so Doppler thought the colour of the light from a star would be altered. The principle was verified experimentally for sound by Buys-Ballot in 1845, but the correct explanation in the optical case was given by Fizeau in 1848. Dop pler's principle is applied to the motion of stars in the line of sight, and is used for the discovery of double stars (see STAR).