On the energy density of the cosmic microwave background

Starting from the assumption that the radiation source at the origin of the cosmic microwave background (CMB) could not have a luminosity larger than the maximum energy in ordinary matter divided by the minimum time allowed by causality, one arrives at an expression that gives the energy density of CMB as a function of the main cosmological parameters. Also, by defining a radiation charge as the hypothetical charge that opposes the congregation of a cloud of particles around a source of electromagnetic radiation, on arrives at another expression for the energy density of CMB that agrees exactly with the measured value for a value of the Hubble constant equal to 72.09 km s⁻¹ Mpc⁻¹. Both expressions are independent of the redshift.