Formulated by Edwin Hubble in 1929, the law states that the redshift in light coming from distant galaxies is proportional to their distance, so that every galaxy appears to be rushing away from us (or from any other point in the universe) with a speed that is directly proportionate to its distance from us. It is considered the first observational basis for an expanding universe (or the metric expansion of space), and the most often cited evidence in support of the Big Bang theory, and arguably one of the most important cosmological discoveries ever made.