Final answer:
The understanding of the Doppler effect is applied to the study of galaxies in astronomy. It helps determine the speed and direction of galaxies by analyzing the shift in the frequencies of light received from them.
Step-by-step explanation:
The understanding of the Doppler effect is applied to the study of galaxies in astronomy. As galaxies move away from us, their light is shifted to a lower frequency, resulting in a longer wavelength, known as the red shift. This shift in the frequencies of light received from galaxies allows astronomers to determine their speed relative to ours. Therefore, the correct statement is that the Doppler effect indicates a galaxy moving away from Earth through red shift.