  A fundamental assumption inherent in the standard Lambda+CDM Hot Big Bang
(HBB) model is that photons lose energy as they are redshifted due to the
expansion of the universe. We show that for the Quasi-Static Universe (QSU)
model, in which photon energy is an invariant in the cosmological reference
frame, the photon number density in the universe today is a factor of
approximately 1600 less than in the standard model. We examine some of the
consequences for a number of processes that occur during the thermal history of
the early universe, including primordial nucleosynthesis, the formation of
neutral hydrogen (recombination), and the evolution of the Cosmic Microwave
Background (CMB) radiation. We show that the QSU model predicts that the
measured CMB photon noise level will be a factor of 40 higher than the level
that would be observed assuming the standard HBB model. The CMB data that will
be collected by the recently launched Planck satellite mission provides an
ideal opportunity to test the validity of this prediction.
