From a Harvard-Smithsonian Center for Astrophysics press release:
Almost 14 billion years ago, the Universe burst into existence in an extraordinary event that initiated the big bang. In the first fleeting fraction of a second, the Universe expanded exponentially, stretching far beyond the view of our best telescopes (see Section 19.5, p. 526).
Researchers announced on March 17, 2014, the first direct evidence for this cosmic inflation. Their data also represent the first images of gravitational waves – ripples in space-time. These waves have been described as the ‘first tremors of the big bang.’ Finally, the data confirm a deep connection between quantum mechanics and general relativity.
These groundbreaking results came from observations by the BICEP2 telescope (pictured above) of the cosmic microwave background – the faint glow left over from the big bang. Tiny fluctuations in this afterglow provide clues to conditions in the early universe. For example, small differences in temperature across the sky show where parts of the Universe were denser, eventually condensing into galaxies and galactic clusters.
Since the cosmic microwave background is a form of light, it exhibits all the properties of light, including polarization. On Earth, sunlight is scattered by the atmosphere and becomes polarized, which is why polarized sunglasses help reduce glare. In space, the cosmic microwave background was scattered by atoms and electrons and became polarized too.
The researchers hunted for a special type of polarization called ‘B-modes,’ which represents a twisting or ‘curl’ pattern in the polarized orientations of the ancient light. Gravitational waves squeeze space as they travel, and this squeezing produces a distinct pattern in the cosmic microwave background. Gravitational waves have a ‘handedness,’ much like light waves, and can have left- and right-handed polarizations. The swirly B-mode pattern is a unique signature of gravitational waves because of their handedness.
The figure above shows the actual B-mode pattern observed with the BICEP2 telescope, with the line segments showing the polarization from different spots on the sky. The red and blue shading shows the degree of clockwise and anti-clockwise twisting of this B-mode pattern.
Links: the Harvard-Smithsonian CfA press release including figures, Caltech press release, NY Times article by Dennis Overbye (including a cartoon explaining inflation), Union-Tribune San Diego article (including cartoon of polarization of light), APOD March 18, 2014 shows the observatory at the South Pole, all BICEP2 public pages.