The “perfect cosmological principle” describes how a model of the universe should look like. This principle requires the model of the universe to be homogenous (the same everywhere) and isotropic (the same in all directions). Many cosmologists apply this principle to space only, but the universe consists of spacetime. Applying the perfect cosmological principle in space and time requires another vision of the Big Bang. The Big Bang cannot be time zero anymore, but must also mean the same thing to all observers at all times. The authors propose a horizon and call it the “Hubble Horizon”.
The relevance of changing the Big Bang to a Hubble Horizon in space-time is great. It means “cosmic inflation” not just in a single era, but throughout the cosmic past. With help of Noether’s theorem it results in an advanced Hubble law for higher redshifted galaxies.