From Genesis to Revelation

The expanding universe model was first championed by the Belgian priest Georges Lemaître, who does not always receive as much credit as he deserves. Lemaître showed how the equations of general relativity predict the universe is expanding, but Einstein was sceptical. Lemaître realized this idea could be tested because spectral lines in light from distant galaxies should be redshifted in an expanding universe and this redshift should be proportional to the distance to the galaxies. Henrietta Leavitt discovered that it is possible to determine the distance to Cepheid variables by measuring the period of their variability. Hubble used this technique to determine the distance to various nearby galaxies and compared this to their redshift data and showed that the universe is indeed expanding.