Johann Christian Andreas Doppler (November 29, 1803 - March 17, 1853) was an Austrian mathematician and physicist, most famous for the hypothesis of what is now known as the Doppler effect which is the apparent change in frequency and wavelength of a wave that is perceived by an observer moving relative to the source of the waves.

Christian Doppler was born in Salzburg, Austria as the son of a stone-mason. However he could not work in his father's business because of his generally weak physical condition. After completing high school he studied astronomy and mathematics in Vienna and Salzburg and started to work at the Prague Polytechnic (now Czech Technical University), where he was appointed professor for mathematics and physics in 1841. (Note: At that time, the present Czech Republic was ruled by the Empire of Austria.)

Only one year later at the age of 39 he published his most notable work on the Doppler effect (for instance to be noticed in the change of sound of a quickly passing vehicle). The German title was "Über das farbige Licht der Doppelsterne und einige andere Gestirne des Himmels - Versuch einer das Bradleysche Theorem als integrirenden Theil in sich schliessenden allgemeineren Theorie" (English translation: On the coloured light of the binary refracted stars and other celestial bodies - Attempt of a more general theory including Bradley's theorem as an integral part) An English translation of his original 1842 work in German can be found in the book by Alec Eden together with the German version. Besides light, Doppler also mentioned sound in his 1842 work. In this work, Doppler tried to explain the colour of binary stars. (Please see reference.) Alec Eden did not feel confident regarding Doppler's conclusions regarding the colour of binary stars but he was confident of Doppler's conclusions regarding the Doppler effect of sound. The Doppler effect of sound was verified by John Scott Russell in 1848. In his time in Prague as professor he published more than 50 articles in mathematics, physics and astronomy. (Note: The Bradley in the title of Doppler's 1842 work is James Bradley of Britain.)

His research career in Prague was interrupted by the revolutionary incidents of March 1848, when he fled to Vienna. There he was appointed head of the Institute for Experimental Physics at the University of Vienna in 1850. During his presence at the University of Vienna, Doppler, along with Franz Unger, played an influential role in the development of young Gregor Mendel who later became the founding father of genetics. (Note: Gregor Mendel studied in the University of Vienna from 1851 to 1853. At that time, Doppler served as a professor there.)

He died from a pulmonary disease in Venice at age 49 on March 17, 1853. His tomb can be found just inside the entrance of the Venetian island cemetery of San Michele. (Note: In 1853, Venice was also ruled by the emperor of Austria. It was like Doppler just moved from one part of the Austrian empire to another part of the same empire. Now Venice is part of Italy and so Doppler's tomb ends up in Italy instead of in Austria.)