> The amount of visible matter corresponds to a CMB temperature that is far lower than what we see. Why would there be a relation between CMB temperature and a

> The amount of visible matter corresponds to a CMB temperature that is far lower than what we see. Why would there be a relation between CMB temperature and amount of (visible+invisible) matter? I suppose the CMB temperature decreases in time. Would`s the relation you talk about imply that the mass or density of mass of the Universe then has to decrease as well?