Who discovered the Doppler effect?

Christian Doppler discovered the phenomenon now called the Doppler effect. The Austrian mathematician and physicist proposed it in 1842 while studying how the motion of stars could alter the apparent colour of their light.

Doppler argued that the observed frequency of a wave depends on the relative motion of its source and the observer. His original astronomical explanation was not entirely correct, but the underlying principle was sound and became fundamental in physics and astronomy.

The idea was later tested with sound. In 1845, Christoph Buys Ballot used musicians on a moving train to confirm that a sound’s perceived pitch rises as the source approaches and falls as it recedes. French physicist Hippolyte Fizeau independently extended the principle to electromagnetic waves in 1848.

Doppler was born in Salzburg in 1803 and died in Venice in 1853. His name now appears in applications ranging from radar and weather observations to medical ultrasound.