Cosmological solutions of the Einstein-Friedmann equations ...

Cosmology
T0 = (2.725 ± 0.002) ◦ K
not only clearly favored Big-Bang cosmologies and essentially ruled out
steady-state theory, it by now provides the best test of isotropy at the level of 0.1%
over 360 ◦ of the sky! We will come to that later.
What does it mean? First we have
ρ0γ = a T 4 0 c2 ✄ ρ0γ 4.64 × 10 −34 gr/cm 3 × c 2 , n0γ 410 photons/cm 3
which confronts with the present baryonic matter density
ρ0,mat 3 × 10 −31 gr/cm 3 × c 2 .
c○ 2009, F. Jegerlehner ≪❘ Lect. 7 ❘≫ 467