A look back at how the dust fell on BICEP2

By Tushna Commissariat

It’s been five days since the metaphorical dust settled on the apparent “discovery” of the B-mode polarization of the cosmic microwave background that was reported in March. The claim came from the team behind the Background Imaging of Cosmic Extragalactic Polarization (BICEP2) telescope at the South Pole, and much has been said since about what was then hailed as one of the biggest scientific discoveries of the decade.

You can read about the team’s claim here and about the controversy here and here. Finally, you can catch up on the most recent update, wherein data from the Planck mission show that BICEP2 may well have been looking at galactic dust, here.

The brouhaha that BICEP2’s press conference in March created was inevitable. Any experiment claiming to have found even the most tentative experimental evidence for primordial gravitational waves – and, in turn, cosmic inflation – is bound to get the attention of the global scientific community. Indeed, there was a nearly palpable tension running through the physics blogs during the weekend preceding the team’s announcement (which was on a Monday).

It seemed that most physicists could not contain their delight over the team’s declaration even though it was unconfirmed and not, at the time, peer-reviewed. Indeed, the BICEP2 team itself inflated (if you will excuse the extremely apt pun) their results with a video (above) of the collaboration informing Andrei Linde (who along with Alan Guth came up with the theory of inflation in the 1980s) of the discovery. In the video, BICEP2 researcher Chao-Lin Kuo, arrives with a bottle of champagne at Linde’s house to tell him “the good news”.

While some of the cosmology community were still busy celebrating the results, doubts began to creep in. Neil Turok, director of the Perimeter Institute for Theoretical Physics in Canada, spoke with me on the very same day as BICEP2 made its announcement to voice his concerns about the claim. Speaking with me again this Monday, in the light of the Planck results, he seemed just as dispirited about the whole situation.  Although he felt right from the start that BICEP2’s claims were excessive, he was more “disappointed but not entirely surprised that leading figures within the community” hailed the finding as the smoking gun for inflation.

Indeed, Turok revealed to me that he had contacted the BICEP2 researchers before they made their announcement publicly and advised them not to make any inferences about their observations. He suggested they not claim that they had found evidence for gravitational waves but rather present their observations as just that – a measurement made to the best of their abilities. Turok believes that they should have “just been an observer” and if they had indeed found the first evidence for gravitational waves, then the team would undoubtedly “get all the credit you deserve” and I can’t help but agree with him.

Adam Falkowski, who writes the Resonaances blog, has also discussed this issue, clearly labelling what he felt the BICEP2 team did right and where they were wrong. He too feels that the “inflation spin” was a faux pas, not to mention the team’s unwillingness to accept the critique for its work that came soon after the announcement and before the paper was finally published in Physical Review Letters. Many physicists have since pointed out that while the claims were slightly toned down in the paper, the peer review was not up to scratch.

But Subir Sarkar, a particle theorist at the University of Oxford and the Niels Bohr Institute in Copenhagen and another of BICEP2’s early critics, has a slightly different viewpoint. He tells me that he feels that it is “the theorists who have been more irresponsible in this matter – both by making overoptimistic ‘predictions’ on the basis of toy models of inflation of a gravitational wave signal that seemed to be detectable with present technology, and secondly by uncritically accepting the BICEP2 claim and generating even more convoluted explanations of how it can be reconciled with other cosmological data”.

While Sarkar agrees that the BICEP2 announcement was pre-emptive, he also says that the “[cosmic microwave background] community had been overly sanguine about the prospect of subtracting galactic foregrounds in order to see the primordial B-mode signals. So this has been a useful wake-up call…although cosmology as a field has made enormous progress observationally in the past couple of decades, it has yet to develop the same maturity and rigour as particle physics in quantifying systematic uncertainties”.

Suffice to say that with the way the entire BICEP2 ding-dong has played out in the public eye, BICEP2 itself is now most likely left with egg on its face. The cosmology community at large is either embarrassed or annoyed and the public is unsure what to believe. But maybe, in some way, this will help give a better and more realistic view of how science is done – someone makes a claim and it is then rigorously checked and re-checked before it can be accepted as scientific fact. But this is normally done behind closed laboratory doors and blind peer-review and only the final “correct” finding is made public.

While the BICEP2 findings’ fate still rests on a knife-edge, what with the ongoing combined analysis with the Planck collaboration, the entire situation has given the physics community a lot to talk, debate and think about.