Given this, we now have to ask, what is the probability that those excited team members did not tell anyone about the big discovery during that month or more, but then did let the cat out the bag in the last few days? Not very big I would argue. Apart from the fact that humans are terrible at keeping secrets, most communication is non-verbal: you can often see when a person is keeping a secret even if they don’t say anything. The team’s work colleagues would have become suspicious… Now perhaps the team is very small and are trained in the 007 techniques of keeping secrets (unlikely, they are physicists after all!), but even if that were the case, why would they have failed at the last hurdle, just days before the formal announcement?
I think a much more likely possibility is that the team have found a hint of something interesting, but not more. A hint doesn’t need to be investigated so deeply, so it would not have slowed publication much. A hint would also mean the team were not so excited about the result, so they would be able to keep their “secret” more easily.
[Update 15/3/14: one way out of this conclusion would be if the analysis was done by a very small team (two or three people perhaps) who were able to keep the secret even from the wider team, while they were doing the cross-checks. The results may have only been disseminated to the team within the last week or two, leading to the sudden spread of rumours this week.]
Now lets look at the priors. These split into two:
(2) Experimental Priors. The probability that a ground-based experiment could make a clean, statistically-significant detection of primordial B-modes given the other ground-based experimental results so far, is arguably rather small [Update 15/3/14: discussions around the experimental capabilities of BICEP2 and KECK/SPUD suggest that it is significantly more powerful than my initial prior estimates, so like any good Bayesian we should update our priors as new info comes in! You can see presentations about the experiments here and here which show how good the projections are. Whether they have reached these levels at this point is speculation.]
(3) Physics Priors: what is the prior theoretical probability that primordial B-modes are large enough to be detected by this experiment? This is tricky since there are so many inflationary models and I won’t comment further other than to say there is no particular theoretical reason to expect the signal to be at the level detectable by this experiment (an argument that has been made against spending money on chasing inflationary B-modes).
When we combine our human-based estimate of the likelihood with these priors, we are unfortunately driven towards the boring end of the spectrum. For the sake of concreteness let me bet that any interesting, robust and unexpected results are below 3-sigma, and more likely around the 2-sigma level; i.e. not statistically significant (yet). Conversely, if there is a claim of a > 3-sigma detection, I suspect that it will be found to be an undiscovered systematic or else it is one that is not robust to changes in the model assumed or priors on parameters. Finally one can be cynical and conjecture that the rumour has been carefully injected into the bloodstream of the cosmology community as a way to create excitement. Nevertheless, even in this case it is hard to imagine them calling a press conference if they had found nothing new, so we can probably put a lower limit on the “hint” of perhaps 1.5-1.8 sigma.
[Update 15/3/14: several sources now put Alan Guth and Andrei Linde at the press conference on Monday, and Andrei is scheduled to give a talk at the joint Tufts/MIT cosmology colloquium on Tuesday. This ups the ante in terms of the above lower limit. How many sigmas do we think would be needed for Alan and Andrei to be invited to, and agree to attend, the press conference? I am not sure, but presumably at least 2-sigma. ]
Of course, even a 2-sigma hint of something exciting would be wonderful (though as Roberto reminded me, a significant fraction of 2-sigma results turn out to be wrong) and it could be that everything I have written is wrong: I certainly hope this is the case…the Universe has proven to be rather boring since 2000 and we desperately need some new excitement. All will be revealed come Monday, so stay tuned!