In the first fraction of a second that followed the Big Bang some 13.8 billion years ago, the universe rapidly expanded far beyond what our contemporary telescopes can see. At least, that was the theory until this week, when a group of scientists on the South Pole discovered the first direct evidence confirming an expanding universe. "Detecting this signal is one of the most important goals in cosmology today," said John Kovac of the Harvard-Smithsonian Center for Astrophysics, which conducted the study.
Cosmic inflation, as it's formally called, released primordial cosmic microwave background radiation that was influenced by gravitational waves, which are described as "miniature ripples in the fabric of space." Albert Einstein’s General Theory of Relativity posited the waves theory, but until now their existence has never been confirmed. Using the South Pole telescope, the team finally detected the gravitational waves in the universe’s "fossil radiation," as well as "telltale polarization signals." From the announcement:
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.
"Our team 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," said co-leader Jamie Bock (Caltech/JPL).
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. This is the first direct image of gravitational waves across the primordial sky," said co-leader Chao-Lin Kuo (Stanford/SLAC).
“This has been like looking for a needle in a haystack, but instead we found a crowbar,” team co-leader Clem Pryke said in a statement, which refers to the discovery as a "smoking gun for inflation." Computer models suggest the universe expanded by 100 trillion trillion times in .0000000000000000000000000000000001 (10 to the minus-34) seconds after the Big Bang explosion.
Harvard theorist Avi Loeb said, "This work offers new insights into some of our most basic questions: Why do we exist? How did the universe begin?"
For further reading, the NY Times has a whole lot more today.