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A �Ӱ���Ƶ professor, two of his graduate students and a former postdoctoral researcher are among a group of scientists whose work was named by Physics World magazine today as one of the Top 10 Physics Breakthroughs of 2013. Physics professor John Ruhl’s team helped design and build sensors and a camera used on the South Pole Telescope and analyze the first year of data, detecting for the first time a subtle twist in oldest light in the universe, called the cosmic microwave background. “There’s a great hope we can use the signal to characterize the growth of structure in the universe,” Ruhl said. “We’ve opened the door, now we have to gather more data to improve the sensitivity of our measurements.” J.T. Sayre, a PhD student working with Ruhl, said, “Being the first experiment to make the detection, when there is a whole range of experiments seeking the same thing, is certainly exciting.” Others involved in the project are PhD student Benjamin Saliwanchik and mechanical designer Rick Bihary of the physics department. Tom Montroy, a former postdoctoral researcher who now works in industry in Boston, was involved in this finding. The top 10 breakthroughs were chosen by the Physics World editorial team, which reviewed more than 350 news articles about advances in the physical sciences published on the magazine website in 2013. (The full announcement about the 2013 breakthroughs can be read on physicsworld.com.) “John and his colleagues have developed exquisitely sensitive detectors and analysis techniques allowing them to unambiguously identify these subtle effects (in which the signal is only about one part in 10 million of the background),” said Cyrus Taylor, dean of the College of Arts and Sciences and a physics professor. “As the measurements get even more precise in coming years, it should provide a unique probe of the energy scale of inflationary models of the early universe, as well as constraining cosmological parameters such as the sum of neutrino masses,” Taylor said. “It is the kind of result where one wants to say ‘Bravo!’"

There’s so much interest in finding twists in the light, called B-mode polarization, because of what they potentially can tell cosmologists, astrophysicists and particle physicists. There are two kinds of B-modes; those found are the brightest set, Ruhl explained. The polarization is caused by the pull of gravity on photons more than 13 billion years old, by massive structures in the universe. Now that they’ve seen them, “We hope we can use them to learn details about how structure grew from the smooth early universe to today, where it’s now lumpy,” Ruhl said. The signals, researchers believe, can be used to map out the matter content of the universe, and, in a kind of reverse engineering, determine the masses of neutrinos. The group is also looking for a slightly different and fainter signal: light polarized in a pinwheel pattern. This would represent a landmark finding that confirms inflation, a key part of the standard cosmological model. “We and other groups are going after it,” Ruhl said, “but it will be harder to detect.” Ruhl’s team worked with researchers from: University of Chicago; McGill University; University of California, Berkeley; Cardiff University, University of Colorado, National Institute of Standards and Technology; California Institute of Technology, NASA’s Jet Propulsion Laboratory; Argonne National Laboratory; University of KwaZulu-Natal, South Africa; University of California, Davis; University of British Columbia; School of the Art Institute of Chicago; University of Michigan; University of Minnesota; Harvard-Smithsonian Institute for Astrophysics; and the University of Toronto. The group is now trying to answer such questions as the age of the universe and how it has changed as it’s aged, the makeup of matter in the universe and whether they can predict how the universe might change in the future.