Cosmic microwave background acoustic peak
= Cosmic microwave background acoustic peak
{c}
{title2=CMB acoustic peak}
{wiki=Cosmic_microwave_background#Primary_anisotropy}
Cosmic microwave background acoustic peaks arise from photon-baryon oscillations caught at successive extrema at recombination. Their approximate phase is set by $kr_s=n\pi$ and their angular positions measure the sound horizon relative to the distance to last scattering.