To apply Hubble's law and find the distance to a galaxy, astronomers need to measure the galaxy's redshift, which is a measure of how much its light has been stretched towards longer wavelengths. This measurement helps determine the amount of the redshift, which enables scientists to calculate the galaxy's velocity, as it is directly proportional to the distance from Earth. By analyzing the correlation between the velocity (due to redshift) and distance, Hubble's law allows scientists to estimate the distance to a galaxy.
