Figure 1: (Left) Design drawing of the BICEP instrument that measures variations in the polarization of the cosmic microwave background at a level of one part in ten million. The $25$-$\text{cm}$ aperture telescope, with an angular resolution of around a half degree at a microwave frequency of $150\text{GHz}$, is designed to limit spurious polarization signals from the instrument at this stringent level. BICEP uses 100 polarization-sensitive bolometers cooled to a fraction of a degree Kelvin to detect the polarized radiation. (Right) Photo of the Background Imaging of Cosmic Extragalactic Polarization (BICEP) experiment, which has given the current best limits on the tensor-scalar ratio $r$ from measuring microwave background polarization alone [12]. Such experiments are working towards measurements of $r$ with precision of $0.01$ that are necessary for strong tests of the bootstrap relations proposed by Boyle and Steinhardt. The image shows the Dark Sector Lab at the South Pole, atop which sits BICEP behind the metal ground shield.