The Friedmann Equations

• expansion rate
• expansion acceleration

A Matter-Only Universe

• cosmic histories plotted

Radiation in the Universe

• photon redshifts
  • (sketched on balloon analogy)
  • redshift recordholders: QSO at z=6.4; GRB at z=8.2; photometric evidence for galaxies at z=8-8.5;
• radiation energy density
• radiation pressure

The Cosmic Equation of State

Minimally Realistic(?) Cosmic Histories

• cosmic ingredients
• limiting cases: matter, radiation, curvature, Lambda domination