A major new study claimed to find direct evidence of the Big Bang and the theory of cosmic inflation. But now scientists aren't so sure
It was just weeks ago that astronomers announced a major, double-barreled discovery: using a super-sensitive microwave telescope known as BICEP2, they had seen evidence of gravity waves that roiled the cosmos before it was a billionth of a trillionth of a second old. That was part one; part two was that the observed gravity waves strongly confirmed the theory of cosmic inflation—that the entire universe went into warp overdrive, expanding faster than the speed of light for the tiniest fraction of a second.
It was Nobel-level work, no doubt about it—provided it was true. But from the moment it was announced at a high-profile press conference, outside scientists had their doubts. There was reason to suspect, they said, that the Harvard-led team might actually have detected nothing more exciting than interstellar dust in the Milky Way. And now a paper expected to go online today, written by Raphael Flauger, of New York University and the Institute for Advanced Study in Princeton, puts those doubts in writing.
The signal may still be from the dawn of time, he writes. But it might equally well be what Princeton University astrophysicist David Spergel calls “schmutz” (in precisely that language: it’s what the Urban Dictionary defines as the Yiddish term “used by Jewish mothers to identify that you’ve got some kind of crap on your face.”) “At this point,” says Spergel, “I’m convinced that they haven’t made a discovery.”
It’s not that anyone doubted the integrity or ability of the Harvard-led team that claimed the discovery. “These guys are no slouches,” says Lyman Page, chair of Princeton’s physics department. “This is a good group. If there’s a problem here, it’s one of enthusiasm.”
And who wouldn’t be enthusiastic? The theory of inflation seemed downright nutty when it was first proposed in the early 1980s by Alan Guth, now at the Massachusetts Institute of Technology. But it explained some mysteries that had stumped astrophysicists for decades, including why the universe looks essentially the same in all directions, and why galaxies and clusters of galaxies are distributed the way they are.
Since then, every observation of the early universe has been consistent with the idea of cosmic inflation–most notably, the ultra-precise maps of microwaves left over from the Big Bang made by the WMAP satellite in 2003. (Both Spergel and Page were involved in that piece of cosmic cartography.) But the BICEP2 measurement was in principle more definitive than most; beyond that, there are many competing versions of inflation theory, and the new results suggested that one of the simplest versions was the right one.
The problem: the signal predicted by inflation is something called polarization, a sort of twisting of electromagnetic radiation. And while it can come from inflation-triggered gravity waves, microwaves from the early universe are altered en route to earthly telescopes, and if you don’t allow for the alteration, you can mistake local dust for a signal from billions of years ago. To correct for dust, the BICEP2 team relied, not on its own observations, but on data from Europe’s Planck satellite. The data were preliminary, however, and the BICEP2 team got them data, not from a database, or even a scientific paper, but from a slide shown at a conference by the Planck team. “It’s all we had to work with,” says Harvard astrophysicist John Kovac, who led the BICEP2 team. Moreover, he says, the Planck slide affects only one of the six models his team to characterize interstellar dust. “That’s wrong,” says Spergel. “It affects five out of the six.”
All of this will be settled within months, as other teams weigh in with their own results—not just Planck, whose formal paper on cosmic dust will be coming out in the fall, but also a host of ground-based and balloon-based microwave telescopes that were racing with BICEP2 to look for evidence of gravity waves themselves. That’s exactly how science should work, says Kovac. “We were primarily focused on getting our measurements out to the scientific community,” he says, and the challenges that follow are a normal part of the scientific process.
Traditionally, peer review of a new result—especially such an important one—doesn’t normally happen in such a public way, and some scientists have criticized the Harvard-Smithsonian Center for Astrophysics (CfA) for holding a press conference to tout it before other scientists have had a chance to weigh in. Christine Pulliam, a public affairs officer at the CfA disagrees. “A finding this profound would have been publicized with or without a press conference,” she told TIME. “By holding one, the team was able to convey all relevant information as a coherent whole, with the appropriate caveats that further research is needed.”
There’s another issue, however, says Princeton’s Paul Steinhardt (a proponent of a theory that competes with inflation, it should be noted—a theory that would be ruled out by the detection of primordial gravity waves) “The BICEP2 team keeps talking about waiting for ‘confirmation’ of their detection. But you cannot confirm unless you first detect. Shouldn’t the record be set straight?”