What is the primary physical cause for the extreme redness observed in very distant galaxies?

Answer

Cosmological redshift stretching the light waves during the expansion of the universe.

Cosmological redshift occurs because the expansion of the universe stretches light waves emitted by distant objects during their long transit time, shifting the entire spectrum toward the red end.

What is the primary physical cause for the extreme redness observed in very distant galaxies?

#Videos

3 Red Monster Galaxies Are So Large They Shouldn't Be Possible

Spacegalaxyastronomyredcosmology