Picture of Christian Doppler
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 what is now known
as the Doppler
. He theorized that sound waves from a moving source would be
compressed or expanded, or that the frequency would change. This theory
wasn't tested until 1845.
In 1845, Buys Ballot set up an experiment using two groups of trumpeters, all
who had perfect pitch. One group set up at a train station while the
other set up on a train car that was to be pull past the station. Both
groups were to play the same note and Doppler's theory stated that the
notes would be dissonant (that the frequencies would be different). This
turned out to be true; the notes were audibly different, even though both
groups of musicians were playing the same note.
Later, a scientist named Fizeau generalized Doppler's work by applying his
theory not only to sound but also to light.
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