What phenomenon describes light shifting toward the longer, redder end of the electromagnetic spectrum?

Answer

Redshift

Redshift is the observation of light waves being stretched toward longer wavelengths, corresponding to the red end of the spectrum, as an object moves away or space expands.

What phenomenon describes light shifting toward the longer, redder end of the electromagnetic spectrum?

#Videos

What Does Redshift Tell Us About Distant Galaxies? - Physics Frontier

galaxyDistanceuniverseexpansionredshift