Abstract: The Cosmic Microwave Background (CMB), the radiation afterglow of the Big Bang, provides us with both a snapshot of the early Universe and a backlight that illuminates all the later-developing structure. The statistics of this light provide avenues to detect beyond-the-standard-model physics from inflationary gravitational waves or light relic particles. The growth of large-scale structure, measured by gravitational lensing of the CMB, provides information on the mass of neutrinos and on dark energy. Both the intensity and the polarization of the microwave light are crucial. Electron scattering of CMB photons allows us to find distant galaxy clusters via their gas content. With good time resolution, CMB surveys can identify and measure variable and transient objects from flaring stars to gamma-ray bursts to supermassive black holes in active galactic nuclei, and can play a role in multimessenger astronomy. I will briefly tour ground-based experimental efforts at the South Pole and in Chile, including the South Pole Observatory, Atacama Cosmology Telescope, Simons Observatory, and their successor, CMB-S4, a project rated highly by the Decadal Survey of Astronomy and Astrophysics.
The College of Arts