Christian Doppler, Austrian physicist, c 1840s.
© Science Museum / Science & Society Picture Library
Doppler (1803-1853) was born in Salzburg, Austria. In 1842 he produced a paper on 'Doppler's principle', explaining the frequency variation observed when a vibrating source of waves and the observer approach or recede from one another. In 1851 he was appointed Profesor of Physics at the Royal Imperial University of Vienna, the first such position to be created in Austria.