... Tutorial : Part 1 | ... Until a few hundred years ago, the Solar System and the Universe were equivalent in the minds of scientists, so the discovery that the Earth is not the center of the Solar System was an important step in the development of cosmology. ... In 1929 Hubble published a claim that the radial velocities of galaxies are proportional to their distance. ... The slope of the fitted line is 464 km/sec/Mpc, and is now known as the Hubble constant, H o . ... Ned Wright's Home Page . ...