Once we have found the speed of a galaxy away from the Earth, it is very simple to find its distance from a Hubble graph (see below). For example, if we find a galaxy that is receding at 50 000 km/s, it is at a distance of 3 thousand million light years . However recent measurements using this technique have suggested that the Universe is only 8 thousand million years old, whereas some stars are thought to be 14 thousand million years old! Therefore, there is still work to be done before this method can be used accurately.
A galactic cluster's distance can be measured this way
Comparing the distance of M100 to its receding speed, astronomers estimate
an age of the Universe of less than some of its oldest stars!
* Click here to learn how astronomers work out the speeds of galaxies away from the Earth