The realization that radio astronomers could detect radio galaxies that were well beyond the limits of even the most powerful optical telescopes suggested that radio observations might be able to distinguish between the two competing cosmological models. The commonly accepted big-bang model required that, since the Universe continued to evolve with time, so the distant (younger) Universe should appear different than the nearby modern Universe. By contrast, the steady-state theory required that the Universe is, and always was, everywhere the same, so distant galaxies should look the same as more nearby galaxies. An intense controversy developed between radio astronomers in Sydney, Australia and Cambridge, UK over the distribution of radio sources and their implication for theories of cosmology. The Australian radio astronomers, who had better data than the Cambridge research workers, found no evidence of cosmic evolution. The Cambridge group, led by Martin Ryle, misunderstood the effects of their instrumental errors and used an incorrect analysis – but got the right answer, arguing that the Universe is evolving with time, contrary to the expectations of the steady state-theory.