[PAR] [TLE] Christian Doppler [SEP] Christian Andreas Doppler ( ; ] ; 29 November 1803 – 17 March 1853) was an Austrian mathematician and physicist.  He is celebrated for his principle — known as the Doppler effect — that the observed frequency of a wave depends on the relative speed of the source and the observer.  He used this concept to explain the color of binary stars. [PAR] [TLE] Doppler effect [SEP] The Doppler effect (or the Doppler shift) is the change in frequency or wavelength of a wave for an observer who is moving relative to the wave source.  It is named after the Austrian physicist Christian Doppler, who described the phenomenon in 1842.
[PAR] [TLE] Christian Doppler [ SEP ] Christian Andreas Doppler ( ; ] ; 29 November 1803 – 17 March 1853 ) was an Austrian mathematician and physicist . He is celebrated for his principle — known as the Doppler effect — that the observed frequency of a wave depends on the relative speed of the source and the observer . He used this concept to explain the color of binary stars . [PAR] [TLE] Doppler effect [ SEP ] The Doppler effect ( or the Doppler shift ) is the change in frequency or wavelength of a wave for an observer who is moving relative to the wave source . It is named after the Austrian physicist Christian Doppler , who described the phenomenon in 1842 .
What year was the phenomenon used to explain the color of binary stars described?
What year was the phenomenon used to explain the color of binary stars described ?
1842
1842