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<-   Applications of the Doppler effect  
figures/decalagerouge.png
Doppler effect
Copyright : Paris Observatory/ ASM / Hale Observatory
vidéo MPEG

A motorbike, which passes near a listener, is a sound transmitter which moves closer to and away from the observer. The sound is more high-pitched during the approach, and deeper when the motorbike moves away.

The dark bands visible in the spectrum of the Sun are also seen in the spectra of galaxies (same physical process), but shifted to the red. In the real data, the arrows indicate the position of the dark bands in three more and more distant galaxies.

The very distant galaxies move away from us at high velocity. Their spectra are shifted very much to the red.