Why do more distant galaxies usually have greater redshifts?

Distant galaxies exhibit greater redshifts primarily due to the expansion of the universe, a phenomenon described by Hubble’s law.12

According to this law, the recessional velocity of a galaxy is directly proportional to its distance from Earth. Because the universe is expanding, space itself is stretching, causing galaxies to move away from one another. This expansion is not an outward movement from a single point, but rather an increase in the scale of space throughout the entire universe.132

As a galaxy moves away from an observer, the light it emits is stretched toward longer, redder wavelengths, a process known as cosmological redshift. Because more distant galaxies are receding at higher velocities due to the cumulative effect of the expansion of space over greater distances, their light undergoes a more significant shift toward the red end of the spectrum. This relationship serves as fundamental evidence that the universe has been expanding since the big bang.213