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Breakthrough as astronomers find Big Bang's smoking gun

Paul Sutherland, Feature writer
Mar 18, 2014, 7:00 UTC

Sen—Scientists have looked back to the very beginning of the Universe by detecting echoes of the first instant after the Big Bang.

A special telescope at the South Pole called BICEP2 has observed ripples in the background of space that were caused by the cosmos's rapid expansion as it suddenly erupted into existence.

The extraordinary breakthrough was revealed at a press conference at the Harvard-Smithsonian Center for Astrophysics (CfA) and came after days of frenzied speculation.

Swirly patterns have been recorded in the faint glow called the Cosmic Microwave Background (CMB) that was left after the Big Bang. They are being described as its “smoking gun”.

Scientists are confident that these twists in polarisation of the CMB, dubbed the B-mode pattern, are a snapshot of gravitational waves that were caused by cosmic inflation, the distortion of space-time as the Universe grew phenomenally in just a trillionth of a trillionth of a trillionth of a second.

The result supports modern cosmological theories and will have a major impact on astronomers’ understanding of how the Universe evolved because they will learn more about the very beginning of its existence.

Big Bang ripples

The faint but distinctive twisting pattern in the polarisation of the cosmic microwave background that echoes the Universe’s creation. Credit: BICEP2 Collaboration

This gravitational signal, predicted by Einstein in his theory of general relativity, has never been directly detected before. He said it would be caused by massive objects interacting, such as when black holes collide.

The scientists, led by John Kovac of Harvard University, describe their confdence in their findings as being “greater than 5 sigma”, which is jargon meaning that the odds of the pattern being there by chance are less than one in 3.5 million.

Chao-Lin Kuo, an assistant professor of physics at Stanford University and SLAC National Accelerator Laboratory, and a co-leader of the BICEP2 collaboration, said: “This is really exciting. We have made the first direct image of gravitational waves, or ripples in space-time across the primordial sky, and verified a theory about the creation of the whole Universe.”

It had been thought that these primordial waves from the origin of the Universe might be undetectable, or that they would be incredibly weak if they were there. So the team collaborating on the BICEP2 project was surprised to find that they were stronger than they expected.

The results have not yet been published in a journal, but the team has spent three years ruling out any alternative explanations for the pattern of swirls, including dust in our own Milky Way, gravitational lensing distortions by other galaxies, or errors introduced by the telescope.

Team member Clement Pryke, of the University of Minnesota, commented: “It is absolutely mind-boggling that we’ve actually found it. In my heart, I did not expect it. I thought we would do this because there’s good physics to be done, and we’d prove that the signal was so small that it wasn’t worth trying any harder. Instead, it is loud and clear.”

Marc Kamionkowski, of Johns Hopkins University, Maryland, said: “This is the greatest discovery of the century. If it sticks, which I think it will, it’s Nobel-prize material.”

BICEP2 is funded by the National Science Foundation and backed by NASA. It was placed in the seemingly inhospitable environment of the South Pole because it is one of the driest regions of the planet.


Graduate student Justus Brevik tests the BICEP2 readout electronics. Credit: Steffen Richter (Harvard University)

Water vapour absorbs microwaves, making detailed studies of the CMB impossible from most places on Earth. However, because the South Pole is so dry, has such low temperatures and is at a high altitude of around 3,000 metres (10,000ft) astronomers say putting a telescope there is the next best thing to being in space.

UK scientists at the University of Cardiff were involved in the construction of the BICEP2 instrument and observations with it over the past three years.

Professor Peter Ade, of Cardiff, told Sen: “The Big Bang is a violent event and gravitational waves will be emitted and that will squeeze and stretch the polarisation signature. The matter in the Universe, the whole of space-time, will be modulated by the gravitational waves and you would see a swirly pattern in this polarised emission.

“It is a real challenge to build an instrument to look for this. But that swirly pattern is what they’ve found. I’ve seen the data and it really is very convincing.”

Professor Ade said astronomers would now be checking data from the European Space Agency’s Planck space telescope, which was switched off last year after 4.5 years scanning the heavens for echoes of the Big Bang.

He told Sen: “The level of the signal that is detected here would be clearly observable in the Planck all-sky maps. Planck has an advantage here in that it covered the whole sky. I would like to see that same signature validated in the Planck data later this year. Once that happens it’s a no-brainer that everyone will accept that, yes, the theory of cosmic inflation is correct.”