Question

redshifts were used as supporting evidence for the big bang theory. which describes redshifts? check all that apply. the light source and observer move closer together. observed light shifts to a longer wavelength. they indicate receding galaxies. observed light shifts to a shorter wavelength. the light source and observer move farther apart. they indicate approaching galaxies.

Explanation:

Red - shifts occur when the light source and observer move farther apart. This causes the observed light to shift to a longer wavelength. Red - shifts indicate receding galaxies. When the light source and observer move closer together, it's a blue - shift.

Answer:

Observed light shifts to a longer wavelength.
They indicate receding galaxies.
The light source and observer move farther apart.