The cosmological redshifts z in the frequencies of spectral lines from distant galaxies as compared with their values observed in terrestrial laboratories, which are due to the scale factor a(t), frequently are interpret as a special-relativistic Dop
pler shift alone. We will demonstrate that this interpretation is not correct and that the contribution of the gravitational redshift is always present and significant. We will show that the gravitational redshift is actually about the same magnitude as the cosmological redshift, but that only for cosmological models without the dark energy component cosmological and gravitational redshift can be considered to be the same. Significant contribution of the gravitational redshift due to the gravitational field of the Universe, which is ignored in interpretation of the observational data, could have significant impact on cosmological theories. We will first calculate contributions of gravitational redshift to CMB and time dilation of Type Ia supernovae, and use it to explain the excess redshifts of quasars and active galaxies, and redshifts of companion galaxies of stars. We will show its possible implications on the interpretation of mass density of matter and mass as function of cosmological time. Finally we will demonstrate that taking into account gravitational redshift allows to interpret luminosity distance and surface brightness of distant galaxies to be consistent with the static universe cosmological models.
