Christian Doppler first presented his paper on the effect on May 25, 1842.
The presentation took place at a meeting of the Royal Bohemian Society of Sciences in Prague. Doppler’s paper was titled “Über das farbige Licht der Doppelsterne und einiger anderer Gestirne des Himmels,” meaning “On the Coloured Light of the Binary Stars and Some Other Stars of the Heavens.” It proposed that the motion of a light source or observer could change the observed frequency and color of light.
Doppler was trying to explain why binary stars might appear to have different colors. His original explanation was not fully correct for the scale of stellar velocities, but the underlying frequency-shift principle was sound. The effect was later tested experimentally with sound in 1845 by Christoph Buys Ballot, using musicians and a moving train.
The paper was published in 1842 in the proceedings of the Bohemian Society. This presentation date is sometimes confused with the publication date or with later experiments that confirmed the effect. The modern Doppler effect now applies to sound, light, radar, medical ultrasound, and astronomical redshift.