An acclaimed "smoking gun" discovery explaining the unfolding of the early universe faces rumors of a cosmic misfire. (See: "Big Bang's 'Smoking Gun' Confirms Early Universe's Exponential Growth.")
In March the Background Imaging of Cosmic Extragalactic Polarization 2 (BICEP2) team headed by Harvard's John Kovac announced a pioneering observation of cosmological "gravitational waves" first predicted by Einstein to headlines worldwide. The claim seemed to confirm the conventional cosmological view of the universe expanding exponentially in its earliest instant.
The cosmologists reported that, using a telescope in Antarctica, they had seen the swirled signatures of these surprisingly strong gravity ripples crisscrossing a portion of the big bang's aftermath—the so-called cosmic microwave background that emanates from every corner of the sky. (Related: "How Will Science Confirm Those Cosmic Signals From the Infant Universe?")
That claim, however, has come under fire. An online particle physics blog post written by physicist Adam Falkowski of the Laboratory of Theoretical Physics of Orsay, France, on Monday reported that "experts now put a finger on what exactly went wrong in BICEP."
Essentially, Falkowski suggests that the BICEP2 team had mixed up the effects of microwaves emitted by dust inside our Milky Way galaxy with those of the microwaves released by dust filling the entire sky. Both kinds of microwaves need to be carefully unmasked and removed from the analysis to observe the gravitational wave ripples seen by BICEP2 in the underlying cosmic microwave background.
While Falkowski claims that the BICEP2 team "has now admitted to the mistake," Kovac and team scientist Clement Pryke of the University of Minnesota have both denied the claim, to Science and New Scientist magazines. Pryke calls it "totally false" in Science, saying the team stands by the result.
In Science, however, Pryke acknowledges that the discovery team's dust map comes from a conference presentation, not published data, made by Europe's Planck satellite, which adds some uncertainty to the results.
Nevertheless, the Antarctica observations are thought to come from a relatively un-dusty part of the sky. And in an April presentation at MIT, Kovac had suggested that early indications from follow-on observations made by the BICEP2 team supported its gravitational wave discovery.
Physicist Marc Kamionkowski of Johns Hopkins University in Baltimore had said the gravitational wave observations were "the smoking gun for inflation," the theory that explains how the early universe smoothly expanded to unimaginable vastness in the first fractional second of its existence.
The BICEP2 results have already weathered an earlier round of criticism on the Internet in April, when three cosmologists claimed that galactic "radio loops" had actually produced the gravitational waves reported by the team. The radio-loop critique seems to have faded off the dial, though, and been replaced by the new rumors.
In October the Planck team is expected to release its own, latest cosmic microwave map, one perhaps sensitive to the gravitational wave effects seen by the BICEP2 team, which may settle the dispute. Other efforts in Antarctica and Chile are also under way, scanning the sky on the same hunt and offering more hope for a final confirmation, or not, of the March results.
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