The recent release of the WMAP three year data [ 1 ] illustrates the extent to which cosmological model - building is now contrained and guided by precision data . It also emphasizes the extent to which a Standard Model of cosmology has emerged . This concordance model is denoted the " power - law ΛCDM model " in [ 1 ] ; a slightly more theory - loaded designation is the " inflation - assisted ΛCDM model " . In this model the universe on large scales is homogeneous , isotropic , and spatially flat . The universe contains matter ( dominated by dark matter ) , radiation , and dark energy . The dark energy consists either of a cosmological constant or of a quintessence field whose equation of state parameter w(t ) is close to −1 now . Primordial density perturbations have a nearly scale invariant spectrum . At scales comparable to the current Hubble radius , the scalar perturbations have a slightly negative spectral tilt [ 1 ] .