The light spectrum from every galaxy includes dark lines. The lines have the same pattern. Figure 7 shows the position of dark lines in the visible spectra of light from the Sun and from two distant galaxies. Explain what these light spectra tell us about the velocities of galaxy A and galaxy B.

The dark lines in the spectrum of light from stars and galaxies correspond to specific frequencies of light being absorbed by elements in the star's atmosphere. 1. **Redshift:** When we compare the spectra of Galaxy A and Galaxy B to the Sun's spectrum, we see that the pattern of dark lines is shifted towards the longer wavelength (red) end. This phenomenon is called redshift. 2. **Velocity:** Redshift is evidence for the Doppler effect with light. It tells us that the light source (the galaxy) is moving away from the observer (us). Therefore, both galaxies are receding from Earth. 3. **Comparison:** The lines in Galaxy B's spectrum are shifted further to the red than those in Galaxy A's spectrum. The size of the redshift is proportional to the recessional velocity. A larger redshift means a greater speed. Therefore, Galaxy B is moving away from us faster than Galaxy A.