Doppler, Christian Johann 1803-53
Austrian physicist

Born in Salzburg, he showed early mathematical ability and after studying at the Polytechnic Institute in Vienna, he was appointed Professor of Mathematics and Accounting at the State Secondary School in Prague. In 1851 he was appointed Professor of Physics at the Royal Imperial University of Vienna, the first such position to be created in Austria. 'Doppler's principle', which he enunciated in a paper in 1842 when he was Professor of Elementary Mathematics and Practical Geometry at the State Technical Academy in Prague, explains the frequency variation observed when a vibrating source of waves and the observer approach or recede from one another. The Doppler effect applies to all forms of electromagnetic radiation and is used in astronomy, where the changing wavelengths of approaching or receding celestial bodies provide important evidence for the concept of an expanding universe.