How do astronomers measure the distance to a galaxy using redshift?

Astronomers compare the observed wavelengths of known spectral lines with their laboratory values to calculate redshift, written as z. For relatively nearby galaxies, the greater the redshift, the faster the galaxy is receding and the farther away it is. This method is rooted in Edwin Hubble’s work in the 1920s and is still central to cosmology today. For very distant galaxies, scientists combine redshift with a cosmological model to convert it into distance because the universe’s expansion has changed over time.