Another method is to examine a galaxy’s white dwarf supernovae luminosities. This provides another “standard” brightness with which we can compare.
Galactic Distance and Position versus Galactic Age
Most of the galaxies are moving away from each other; each with a velocity of V. This infers that the galaxies must have been closer together at one time. Recall that Hubble’s Law is a relationship between velocities and distances, and is related to expansion through the Hubble Constant, H o .
This goes back to rearranging Hubble’s Law V = H o to d = v/H o and allows us to infer not only the age of galaxies, but the Universe itself, time. We have a good idea at the value of H o . So let’s say we can determine how far galaxies are away at varying distances, d . We already know the velocity, V , from determining the distance; this is the velocity each galaxy is moving. Since you know the velocity and distance, use a simple formula and you can now calculate the time.