B-modes rocketed to fame in March 2014, when a team of scientists working on an experiment called BICEP2 announced the first direct evidence for primordial gravitational waves rippling out from the earliest moments of the universe: a distinctive imprint in the cosmic microwave background (the light left over from the Big Bang) called "B-mode polarization," or B-modes for short. Polarization describes the way that light-waves are oriented, and B-mode waves are twisted into a swirling pattern. The detection of these swirls was a stunning confirmation of the theory of cosmic inflation. Suddenly, B-modes were electromagnetic celebrities.
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