Cosmic Inflation Again

I hate to say “I told you so,” but … oh, never mind.

One of the problems that the big bang model suffers from is the horizon problem. For three decades the solution to this problem has been cosmic inflation, a hypothetical far-faster-than-light expansion in the very early universe (perhaps as early as 10^-34 seconds after the big bang). Because cosmic inflation is so needed to solve the horizon and other problems with the big bang model, most cosmologists and astronomers long ago accepted it. This was despite that fact that there was no evidence for cosmic inflation. That situation supposedly changed last March 17 with the much-celebrated announcement that a group of researchers had discovered the first evidence of cosmic inflation. The BICEP2 (Background Imaging of Cosmic Extragalactic Polarization) team revealed that they had measured feeble B-mode polarization in the CMB (cosmic microwave background). According to the theory, inflation ought to have imprinted B-mode polarization onto the CMB.

However, there is a problem: dust within our Milky Way galaxy can produce polarization that mimics the signal allegedly produced by cosmic inflation. In fact, scarcely a week after the press release by the BICEP2 team, other scientists had begun to question whether dust could be responsible for the claimed signal. The BICEP2 researchers had attempted to estimate the effect of dust upon their measurements, but the best data to do this were not yet available. The Planck satellite consortium later released the relevant data. On January 30, 2015, members of BICEP2, Planck, and the Keck Array (an experiment similar to and associated with BICEP 2) submitted a joint paper to Physical Review Letters. Numerous press accounts of this story are available, mostly drawing upon the press release from ESA (the European Space Agency) that oversees Planck, but the preprint of the paper submitted to Physical Review Letters also was available. In their paper, the scientists concluded that the B-mode polarization previously reported by the BICEP2 team probably resulted from dust, not cosmic inflation. The inclusion of the BICEP2 team in writing this paper amounts to a retraction of their earlier paper.

On the day that the BICEP2 team announced their result last March, Answers in Genesis published a brief response that I wrote. I also blogged about it eight days later. In that response, I offered three cautions. First, I reminded people that a decade earlier a similar claim of evidence for cosmic inflation had been based upon a misunderstanding, so I suggested that this new claim could be misunderstood as well. Second, I commented how extremely model-dependent that this result was. If one were to change the big bang model, the inflation model, or even some of the models used in handling the data (such as the contribution of dust), then the evidence for cosmic inflation could disappear. Third, I cautioned that some other mechanism could mimic the expected signal of inflation. I did not suggest what that mechanism might be, but within a week other, non-creationist scientists were suggesting dust as the mechanism that could do this. Now this latest report bears out the wisdom of what I had written, because it appears that most cosmologists now will accept the conclusion that dust mimicked the signal claimed as evidence for cosmic inflation.

Right after we published our response on March 17, some of our critics attacked it—some mockingly. (See my May 30, 2014, blog about that.) It now is clear that my analysis of this “Nobel Prize level” work about cosmic inflation probably was correct. However, I seriously doubt that the critics who mocked us here at Answers in Genesis over this will run a correction, let alone apologize.