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Why did distant radio galaxies challenge the steady-state theory?

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The steady-state theory proposed that the universe maintains a constant average density and that its large-scale properties, including the population of specific types of objects, remain constant over time.12

During the 1950s and 1960s, astronomer Martin Ryle used radio telescopes to conduct counts of extragalactic radio sources. He discovered that there were significantly more radio galaxies at large distances from Earth than could be explained by a uniform spatial distribution.2

This observation implied that radio galaxies evolve over time, with more powerful sources existing in the past than in the present. Because the steady-state theory required the universe to appear the same at all times, the evidence of an evolving population of galaxies directly contradicted its fundamental tenets. This discrepancy served as a major observational challenge to the theory, eventually leading the scientific community to favor the big-bang model.23