In a lot of ways, the OPERA fast-neutrino business has been less a story about science than a story about the perils of the new media landscape. We went through another stage of this a day or two ago, with all sorts of people Twittering, resharing, and repeating in other ways a story that the whole thing has been explained as a relativistic effect due to the motion of GPS satellites. So, relativity itself has overthrown an attack on relativity. Huzzah, Einstein! Right?
Well, maybe. I’m not quite ready to call the story closed, though, for several reasons. First and foremost is the fact that the primary source I’ve seen cited touting this as the final word on fast neutrinos is a Physics Arxiv Blog, which is emphatically not a reliable source. Despite the name, it is not in any way affiliated with the arxiv itself, and while it is hosted by MIT’s house magazine, the author is not an MIT physicist, but a science writer.
Those issues are confusing to a lot of non-physicists, making it seem like a much more definitive statement than it actually is. Professional physicists and regular readers of the blog know, though, that it consistently shows a sort of New Scientist credulity regarding whatever exotic claim is being made by a new paper. I don’t trust the Arxiv Blog to correctly evaluate the technical merits of a preprint.
Secondly, none of the stories I’ve seen about this (and I admit, I haven’t read all of them) contain any actual journalism. By which I mean that none of them include any comments from anyone associated with OPERA asking whether they think the claim has any merit. Which means that even taking the Arxiv Blog out of the equation, what we have here is a single-author preprint from somebody in the Department of Artificial Intelligence at a Dutch university, claiming to have found an issue that was missed by a large collaboration of physicists. Which is possible, but not what I’d call a rock-solid case. Until I hear something from people associated with the original measurement acknowledging that this is a possible solution, I’m going to remain skeptical.
Which brings us to the final issue, which is a sociology-of-science sort of problem, which is that for this to be the explanation would require a whole bunch of people to be idiots. As Tom notes the error described here seems like the sort of thing that would need to be accounted for in GPS in the first place– the timing error involved is around 32 ns, which corresponds to a position error of around 10m, and GPS routinely does better than that. Tom’s an atomic clock physicist, and has some familiarity with this stuff, so I’m inclined to give his opinions a little more weight than random people from outside physics.
I think the author of the preprint is also confused about the way the experiment worked. That is, he seems to be assuming that all of the timing information comes from the GPS clocks, which are moving relative to the experiment, when in fact the actual event timing comes from clocks on the ground that are at rest with respect to the source and detector. GPS is used to synchronize the ground-based clocks, and to measure the distance between source and detector, but the clocks doing the actual time measurement are in the same moving frame as the experiment itself. But I could be misreading his argument.
(There’s still an issue here, of course, as Matt McIrivn reminded me on Google+, because it’s impossible to perfectly synchronize clocks in a rotating frame, but that doesn’t seem to be what this attempted explanation is about.)
Of course, assuming that the OPERA scientists are a pack of idiots isn’t limited to journalists and AI researchers– lots of theoretical physicists seem to think the same thing, which is kind of depressing. One of the usual suspects in this area actually suggested that the explanation might be that they had failed to account for the probabilistic decay of the muons into neutrinos in the beam, instead putting in a single definite decay time for all of them. This is, frankly, kind of insulting to experimentalists in general. It’d be a little like me saying “Well, I bet your calculation of the vacuum energy is off by 120 orders of magnitude because you forgot to carry the 2 when you added a couple of numbers.” Most of the other suggestions I’ve seen made have been better than that, but still far too quick to assume the worst of the OPERA collaboration.
So, look, the OPERA result is almost certainly going to turn out to be an error of some sort. It might even be some subtle relativistic correction that was left out. But please, try to start your search for an explanation with the assumption that the experimenters aren’t complete idiots. Whatever’s wrong is probably going to be kind of subtle– especially since MINOS saw a similar anomaly, though with worse statistics, back in 2007– and not something that will seem blindingly obvious once it’s discovered.