How do astronomers detect the movement of galaxies?
A) the shift in spectral lines of the galaxies
B) the steady dimming of the galaxy's light
C) the rapid brightening of the galaxy's light
D) the disappearance of the most distant galaxies as they move past the cosmic horizon

Question

Quizplus · Accepted Answer

Astronomers detect the movement of galaxies primarily through the Doppler effect, which causes a shift in the spectral lines of the galaxies. This shift indicates whether a galaxy is moving towards or away from us.

How Do Astronomers Detect the Movement of Galaxies