perfect cosmological principle

The perfect cosmological principle is an extension of the cosmological principle, which states that the universe is homogeneous and isotropic on a large scale. The perfect cosmological principle adds that these properties are constant over time. This idea was central to the steady-state theory of cosmology, proposed by Hermann Bondi, Fred Hoyle, and Thomas Gold in the 1950s. This theory suggested that the universe, while expanding, maintained a constant average density by continuously creating new matter. However, the discovery of the cosmic microwave background radiation in 1965 provided strong evidence for the Big Bang theory and contradicted the steady-state model. The Big Bang theory, supported by observations of the universe's expansion and the abundance of light elements, became the standard model of cosmology.123