 By the early 1960s we had a consistent theory for how the universe scaled over time with three basic curvature models. Observation of galaxy counts at different distances indicated that the flat model was the best fit. And Type 1A supernova studies gave us a good reading on the value of the Hubble parameter at the current time. But the Big Bang theory was challenged by a steady state cosmology that held that the cosmological principle was true for all observers and for all time. Galaxy Redshift was explained as photons losing energy to space rather than space expanding. Plus the supporters argued that a Big Bang would have left a trace that should be detectable. But nothing had been found. It all changed when the cosmic microwave background radiation was discovered in the mid-60s.