Adventures in Friedmann Cosmology: An Educationally Detailed Expansion of the Cosmological Friedmann Equations

The general relativistic cosmological Friedmann equations that describe how the scale factor of the universe evolves are expanded explicitly to include energy species not usually seen. The evolution of a universe as indicated by the Friedmann equations when dominated by a single, isotropic, stable, static, perfect-fluid energy species are discussed and compared. These energy species include phantom energy (w < −1), cosmological constant (w = −1), domain walls (w = −2/3), cosmic strings (w = −1/3), normal matter (w = 0), radiation and relativistic matter (w = 1/3), and a previously little-discussed specie of energy called “ultralight” (w > 1/3). A very brief history and possible futures of Friedmann universes when dominated by stable energy species