An astronomer observes many galaxies in distant parts of the sky to have emission lines redshifted relative to the same lines seen in a laboratory.What is the most likely explanation?
A) Space is expanding.
B) The galaxy is experiencing gravitational lensing.
C) The galaxy has a strong wind.
D) The galaxy is moving through space away from the Milky Way.

Question

Quizplus · Accepted Answer

The redshift of emission lines is a common observation in astronomy and is explained as a result of the expansion of the universe. As the galaxies are moving away from us, the light they emit is stretched out, resulting in a redshift of the observed lines.

An Astronomer Observes Many Galaxies in Distant Parts of the Sky