Cosmic Microwave Background (CMB) photons are actually sensitive gravimeters. Using the intensity and polarization properties of these primeval photons, we can measure the gravitational field of the last scattering surface, the fictitious shell formed by the universe’s first hydrogen atoms.
The last scattering surface is also a gravitational wave detector; a thin “film” of matter onto which primordial gravitational waves can be “exposed”, allowing us to peer back to the inflationary epoch when these gravitational waves themselves were produced. If inflation produced a gravitational wave background, then these gravitational waves imprint a unique “swirling” pattern called B-mode polarization.
IF B-mode polarization is proven to be primordial it will be strong evidence that inflation occurred. This is the goal of a dozen experiments planned, or currently plying southern hemisphere skies: including two experiments whose results will be discussed: BICEP2 and POLARBEAR, the first experiments to directly detect the CMB’s B-mode polarization.
Current experimental sensitivities are at the tens of nanoKelvin level, unimaginable just a decade ago when the hunt for B-modes began. Dr. Keating will discuss the fundamental science that can be revealed with such precision instrumentation.