Figure 1
APS/Alan Stonebraker

Figure 1: When the cosmic microwave background (CMB) originated 13.7 billion years ago (represented by the map on the left), it was polarized with radial and tangential patterns around hot (red) and cold (blue) regions, respectively. This E-mode polarization has been previously observed in CMB measurements. However, gravitational lensing from intervening matter (purple) causes a slight twist in the primeval pattern (shown in the map on the right). This B-mode polarization has been detected for the first time by the SPT Collaboration.