Transcript: The distances to galaxies are measured by a range of indicators, and the most distant galaxies are only measured using redshift as the distance indicator. Thus we need a model for the expansion of the universe, the Hubble expansion, to estimate the distance to the most distant galaxies. For nearby galaxies we can use individual stellar types, especially the most luminous dying stars, supernovae, to estimate distances according to the inverse square law and an assumption that those stars are similar in the distant object as they are within our own galaxy. Without a distance to a galaxy, it’s impossible to get a true measure of its size, its mass, or its luminosity.