Christian Andreas Doppler was an Austrian mathematician and physicist. He is celebrated for his principle — known as the Doppler effect — that the observed frequency of a wave depends on the relative speed of the source and the observer. He used this concept to

explain the color of binary stars. 

Born: November 29, 1803, Salzburg, Austria Died: March 17, 1853, Venice,

Italy Full name: Christian Andreas Doppler Known for: Doppler effect