Cosmic microwave background Dark matter

the cosmic microwave background wmap

although both dark matter , ordinary matter matter , not behave in same way. in particular, in universe, ordinary matter ionized , interacted radiation via thomson scattering. dark matter not interact directly radiation, affect cmb gravitational potential (mainly on large scales), , effects on density , velocity of ordinary matter. ordinary , dark matter perturbations therefore evolve differently time, , leave different imprints on cosmic microwave background (cmb).

the cosmic microwave background close perfect blackbody, contains small temperature anisotropies of few parts in 100,000. sky map of anisotropies can decomposed angular power spectrum, observed contain series of acoustic peaks @ near-equal spacing different heights. series of peaks can predicted assumed set of cosmological parameters modern computer codes such cmbfast , camb, , matching theory data therefore constrains cosmological parameters. first peak shows density of baryonic matter, while third peak relates density of dark matter, measuring density of matter , density of atoms.

the cmb anisotropy first discovered cobe in 1992, though had coarse resolution detect acoustic peaks. after discovery of first acoustic peak balloon-borne boomerang experiment in 2000, power spectrum precisely observed wmap in 2003-12, , more precisely planck spacecraft in 2013-15. results support lambda-cdm model.

the observed cmb angular power spectrum provides powerful evidence in support of dark matter, precise structure fitted lambda-cdm model difficult reproduce competing model such mond.