In the first fraction of a second after the birth of the Universe, space underwent a period of superluminal expansion which we call cosmic inflation. The theory of cosmic inflation was originally proposed in the 1980s to explain the observed geometry and smoothness of the universe. The residual quantum fluctuations from this epoch of inflation seeded the formation of structure in the Universe and left behind a relic background of gravitational waves. These gravitational waves imprint a unique pattern of polarization onto the cosmic microwave background which was recently detected by the BICEP2 experiment operating at the South Pole. This groundbreaking discovery indicates that the epoch of cosmic inflation occurred t~10^-36 seconds after the Big Bang. The energy-density of the universe at this epoch was thirteen orders-of-magnitude larger than the energies probed by the LHC and near the grand-unification scale, where the strengths of the strong, weak and electromagnetic forces are thought to converge. The detection of this signal is a revolution in our understanding of the beginning of the Universe. It ties together the most disparate scales possible in science: quantum mechanics and cosmology; the beginning of the universe to the present day.It is perhaps the most important scientific discovery of this century.
In this talk we will describe the cosmological context of the BICEP2 discovery for non-experts. We will begin with a brief introduction to observational cosmology and the experimental and technological advances that made the detection of cosmic inflation possible. We will conclude by discussing the cosmological implications and the challenges for inflationary theory that this discovery presents.