Hubble’s law
Image: Graph from Hubble’s 1929 paper showing that the further away objects are, the faster they move away from us.
The notion of an expanding Universe in general follows from the equations of General Relativity, shown by Georges Lemaitre in 1927. He also compared this theoretical prediction with observations of ‘extragalactic nebulae’ (now known to be other galaxies), and found that indeed they appeared to move away from us at increasing speed with distance as predicted. Edwin Hubble added more detailed measurements and in 1929 decisively showed that the Universe is expanding – one of the most profound discoveries about the Universe of the last century.
Links
Multimedia
BBC programmes on Hubble’s Law >
Neal Weiner, Redshift and Hubble's law >
