The tumultous period after the original announcement that the BICEP2 experiment had supposedly detected strong evidence of cosmological inflation in the form of B-mode polarization in the cosmic microwave background brought a lot of excitement and speculation. It seems that now, more than half a year later, the dust is finally starting to settle (har-har-har).

In all seriousness though: There have been a lot of rumor going around about the possibility that BICEP2's signal could be purely due to dust. At my university, one of the founding fathers of inflationary theory has been publicly proclaiming that the BICEP2 experimenters are 'crap', and that the claimed discovery is 'nonsense'. With the new data release by Planck, it may be time for a new, possibly decisive, analysis of the claimed discovery. Was it real? Was it dust? Is there still room for speculation?

I'm looking for an in-depth exposition of the credibility of the BICEP2 'discovery' of B-mode polarizations, in light of the latest data (if anyone feels other data than Planck latest dataset is relevant here, feel free to discuss it!). How much, if any, faith should we still put in the claimed discovery? Can (part of) the signal be dismissed as coming from galactic dust? Have we seen inflation?

  • $\begingroup$ Related: physics.stackexchange.com/q/103951 $\endgroup$
    – Art Brown
    Dec 20, 2014 at 17:35
  • $\begingroup$ In their publication already part of the signal had been subtracted to account for the dust. $\endgroup$
    – anna v
    Dec 20, 2014 at 17:37
  • 2
    $\begingroup$ @annav: that claim, given Planck data, is kinda bogus. They've underestimated the amount of dust in their tiny sector of the sky (see this article, for instance). $\endgroup$
    – Kyle Kanos
    Dec 20, 2014 at 18:00
  • $\begingroup$ They were told before the publication that it's going to be a face plant, weren't they? It wouldn't be the first time that this kind of thing happened because somebody had their eye on the Nobel rather than the data. FTL neutrinos, cold fusion... we could probably collect material for a ten volume work about scientists too eager to publish. What does this tell us, really? The obvious: even scientists are just people. $\endgroup$
    – CuriousOne
    Dec 20, 2014 at 18:38
  • $\begingroup$ @CuriousOne Were they? Where are you getting this story? $\endgroup$
    – Danu
    Dec 20, 2014 at 18:39

1 Answer 1


OK, I found a recent link:

Planck versus BICEP2

Despite the new data, the collaboration did not give any insights into the recent controversy surrounding the possible detection of primordial "B-mode" polarization of the CMB by astronomers working on the BICEP2 telescope. If verified, the BICEP2 observation would be "smoking-gun" evidence for the rapid "inflation" of the early universe – the extremely rapid expansion that cosmologists believe the universe underwent a mere 10^–35 s after the Big Bang. A new analysis of polarized dust emission in our galaxy, carried out by Planck earlier in September, showed that the part of the sky observed by BICEP2 has much more dust than originally anticipated, and while this did not completely rule out BICEP2's original claim, it established that the dust emission is nearly as big as the entire BICEP2 signal. Both Planck and BICEP2 have since been working together on joint analysis of their data, but a result is still forthcoming.

This article was updated on 5 December 2014

Now as the BICEP2 paper had used published Planck data available at that time on the dust in their window of the sky, maybe this means that Planck had underestimated dust at that time? The forthcoming paper should surely clear this up.

  • $\begingroup$ That's a great answer, Anna. I think that your "...means that Planck had underestimated dust at that time" almost certainly sums it up: these guys seemed to have used the best data at the time, so the quality of their research is undiminished. They are more likely simply unlucky rather than "crap" (I can't believe how talented scientists, who should be rejoicing in their own achievements, still seem to get off on putting others down) and moreover, the fact that they made the error and reworked the analysis will definitely pave the way for more decisive results in the future. $\endgroup$ Dec 20, 2014 at 23:12

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