A Cosmologic Model Based on the Equivalence of Expansion and Light Retardation

Proceeding from a homogeneous and isotropic Friedmann universe a conceptional problem concerning light propagation in an expanding universe is brought up. As a possible solution of this problem it is suggested that light waves do not scale with R(t). With the aid of a Generalized Equivalence Principle a cosmologic model with variable "constants" c, H, and G is constructed. It is shown that with an appropriate variation of the Boltzmann "constant" k the thermal evolution of the universe is similar to the standard model. It is further shown that this model explains the cosmological redshift as well as certain problems of the standard model (horizon, flatness, accelerated expansion of the universe). PACS numbers: 98.80.Bp, 98.80.Hw, 04.20.Cv. Keywords: cosmology, velocity of light, expansion.