The Cosmic Microwave Background

The coupling of baryons and photons by Thomson scattering in the early universe leads to a rich structure in the power spectra of the cosmic microwave background photons and the matter. The study of these "echoes of gravity" has revolutionized cosmology and allowed precise measurement of a host of important cosmological parameters. I will discuss how far we've come since the early detections of CMB anisotropies, what we've learned from the Planck mission, and what comes next.