Measurements of the Cosmic Microwave Background (CMB) have been extremely important for our understanding of the origin, contents, and evolution of the universe. Increasingly precise maps of the CMB are a unique and powerful tool for understanding new physics, including inflation, the superluminal expansion of the universe during the first moments after the Big Bang. I will discuss the current status of CMB measurements, focusing on constraints on inflation with the BICEP series of experiments at the South Pole (BICEP2, The Keck Array, and BICEP3). I will then discuss the rapidly moving plans for a next-generation ground-based program called CMB-S4. The sensitivity leap of CMB-S4 is needed to pass critical thresholds in our understanding of inflation, neutrino mass, and in searches for additional light relativistic species.
Host: Nevin Weinberg