A cosmological model developed by Fred Hoyle, Thomas Gold and Hermann Bondi in 1948 as the main alternative to the standard Big Bang theory of the universe. Steady state theory holds that the universe is expanding but that new matter and new galaxies are continuously created in order to maintain the perfect cosmological principle (the idea that, on the large scale, the universe is essentially homogenous and isotropic in both space and time), and therefore has no beginning and no end. The theory was quite popular in the 1950s and 1960s, but fell out of favour with the discovery of distant quasars and cosmic background radiation in the 1960s.