Christian Doppler

Picture of Christian Doppler Image courtesy of the University of St. Andrews, Scotland Christian Doppler was an Austrian mathematician who lived between 1803-1853. He is known for the principle he first proposed in Concerning the coloured light of double stars in 1842. This principle is now known as the Doppler Effect. He hypothesised that the pitch of a sound would change if the source of the sound was moving. Doppler's hypothesis was tested by Buys Ballot in 1845. He used two sets of trumpeters: one set stationary at a train station and one set moving on an open train car. Both sets of musicians had perfect pitch and held the same note. As the train passed the station, it was obvious that the frequency of the two notes didn't match, even though the musicians were playing the same note. This proved Doppler's hypothesis. Later, a scientist named Fizeau generalized Doppler's work by applying his theory not only to sound but also to light.

How could Doppler tell the frequency of the notes had changed?

Last modified January 22, 2009 by Julia Genyuk.
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