What phenomenon, when analyzing the light from distant galaxies, indicated that these objects were moving away from the observer?

Answer

Redshift

Redshift occurs when the spectral lines emitted by an object shift toward the red end of the spectrum. In the context of the Doppler effect, this spectral shift provides evidence that the light source is receding from the point of observation.

What phenomenon, when analyzing the light from distant galaxies, indicated that these objects were moving away from the observer?
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