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Nature: Astronomers have detected a long-predicted polarization signal in the ripples of the Big Bang. The signal, known as B-mode polarization, is caused by the gravitational tug of matter on microwave photons left over from the Big Bang. Its detection, posted this week to the arXiv preprint server and made by a microwave telescope at the South Pole, raises hopes that the signal can be used to map out the matter content of the Universe and determine the masses of the three types of neutrinos — in effect, using astronomy to achieve a key goal of particle physics. The detection also suggests that it might be possible to detect another type of B-mode, which would be evidence that the Universe, in the moment after the Big Bang, underwent a wrenching expansion known as inflation. “The reason no one’s been able to see this before is that it is a very small signal — about 1 part in 10 million,” says, an astrophysicist at McGill University in Montreal, Canada, who led the work, which used ultrasensitive microwave receivers on the 10-metre South Pole Telescope (SPT).

(PHOTO: South Pole telescope - Wikimedia Commons)