The cosmic microwave background (CMB) radiation reports the initial conditions in the universe for the formation of large scale structures (galaxies and their dark matter halos, clusters of galaxies). The rich angular power spectrum of the CMB's intensity, combined with measurements of the universe's expansion rate with supernovae and/or other ``nearby" phenomena (relative to the primordial CMB), provides a remarkably explicit picture of the large scale dynamics and contents of the universe. Until recently, the most sensitive measurements of the CMB power spectra have only probed angular scales > 1/3 degree. Now, the Planck satellite has released higher resolution data, and two special-purpose large telescopes, ACT and SPT, have produced maps of the CMB with arcminute resolution. The next step is for each to produce even more sensitive maps with polarization-sensitive receivers. At such small angular scales, the CMB carries additional information about conditions at the epoch of last scattering (Neff, Yp) and before (r, ns, dns/dlnk), as well as information about the evolution of the structure in the universe which can answer questions on topics as diverse as the nature of the dark energy and the sum of the neutrino masses. I will provide a snapshot of the latest results, with an emphasis on ACT.
Received Apr 4, 2013