Tremors from cosmic discovery reverberate through Kavli Institute

Scientists at the University of Chicago’s Kavli Institute for Cosmological Physics are celebrating Monday’s headline-making announcement that astronomers have acquired the first direct evidence of gravitational waves rippling through our infant universe during an explosive period of growth called inflation.


Researchers from the BICEP2 collaboration Monday announced the first direct evidence for this cosmic inflation. Their data also represent the first images of gravitational waves, or ripples in space-time. These waves have been described as the “first tremors of the Big Bang.” On Wednesday afternoon, nearly 200 UChicago scientists assembled in Kersten Science Teaching Center for a special symposium presented by three BICEP2 collaborators (see accompanying video).

“Detecting this signal is one of the most important goals in cosmology today. A lot of work by a lot of people has led up to this point,” said John Kovac, PhD’04, of the Harvard-Smithsonian Center for Astrophysics and leader of the BICEP2 collaboration. The collaborations’ co-leaders are Jamie Bock of the California Institute of Technology, Chao-Lin Kuo of Stanford University, and Clem Pryke of the University of Minnesota.

Funded by the National Science Foundation, BICEP2’s many collaborators include three members of the Kavli Institute: Abigail Vieregg, assistant professor in physics; Christopher Sheely, PhD’13, Kavli Institute fellow; and Erik Leitch, senior research associate.

“What an amazing discovery. The BICEP2 results are truly fantastic,” said John Carlstrom, the S. Chandrasekhar Distinguished Service Professor in Astronomy & Astrophysics, who leads a competing project, the South Pole Telescope. “It is a fantastic day for cosmology and indeed for all of physics.”

Carlstrom served as Kovac’s graduate-school mentor. In 2002, Kovac was lead author of a Nature paper announcing the detection of a minute polarization of the cosmic microwave background using a radio telescope called the Degree Angular Scale Interferometer. The discovery verified the framework that supported modern cosmological theory, including cosmic inflation, which improbably proposed that the universe underwent a gigantic growth spurt in a fraction of a second after the Big Bang.

Tiny fluctuations, big clues

The dramatic new results came from observations by the BICEP2 telescope of the cosmic microwave background—afterglow 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.

Gravitational waves leave behind characteristic twisting patterns on the cosmic microwave background known as B-mode polarization. Researchers took an important first step toward measuring inflationary B modes last year when they detected B modes from gravitational lensing for the first time. Gravitational lensing is a phenomenon that occurs when the trajectory of light is bent by massive objects in space, much like a lens focuses light.

The detection of gravitational lensing B modes was published last September in Physical Review Letters by a multi-institutional collaboration of researchers led by Carlstrom. They used data from SPTpol, a polarization-sensitive camera installed on the South Pole Telescope in January 2012. Physics World magazine named this finding as named one of the top 10 physics breakthroughs of 2013.

Journalists and members of the public alike have displayed enthusiastic interest in Monday’s inflationary B modes announcement. The story made the front page of Tuesday’s New York Times, which quoted Carlstrom in a story headlined “Space Ripples Reveal Big Bang’s Smoking Gun.”

The Washington Post’s coverage, meanwhile, included quote from Kavli Institute Director Michael Turner, the Bruce and Diana Rauner Distinguished Service Professor in Astronomy & Astrophysics. “Inflation—the idea of a very big burst of inflation very early on—is the most important idea in cosmology since the big bang itself,” Turner hold the Post. “If correct, this burst is the dynamite behind our big bang.”

Other coverage included a live interview with BICEP2 collaborator Vieregg on WBEZ’s Afternoon Shift program. “It’s great to watch the reaction of our community,” Vieregg said during the interview. “Our website that has our data and papers on it has actually gotten three and a half million hits as of last night.”

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