Queen Emmy the Physics-Taught Dog on Superluminal Neutrinos
Queen Emmy:
Faster Than a Speeding Photon: "Measurement of the neutrino velocity with the OPERA detector in the CNGS beam" : Uncertain Principles: there's still room for a canine-level write-up going into a bit more depth about what they did and where it might be wrong.
So, what did those jokers at CERN pull this time? Isn't it bad enough that they want to feed us all into a black hole, now they're messing with the speed of light?… The neutrinos are created at CERN in one of their three varieties, and on the way to Gran Sasso, they can change character and end up being detected as a different type…. As part of the preliminary analysis for their main experiment, they looked at about three years worth of data, and noticed something odd: the neutrinos in their experiment seem to be moving slightly faster than the speed of light…. [T]he difference they see is many times larger than their uncertainty, and they can't figure out why…. [T]hey do is to compare the distribution of times when they detect neutrinos to the distribution of times when neutrinos were created in the source…. [T]he time of flight… is about 60ns too short, suggesting the neutrinos were moving faster than they speed of light….
How about the distance? Could they have screwed that up? That's the other obvious source of error, but it's hard to see how. Again, they have GPS to use for this, and while the accuracy of the position obtained by GPS for a moving receiver, like in your phone, is only several meters, if you're trying to measure the distance between two fixed points, and monitor it over a long time, you can get really good accuracy. They claim to have the distance down to 20cm, which is a bit less than a nanosecond at the speed of light. Twenty centimeters? Really? Really. They even provide a graph showing their measurements over the three-year run, which pick up a slow change due to continental drift, and a dramatic jump due to an earthquake in 2009….
So, what else could be wrong? Well, that's the problem. They've checked all the obvious things, and they all seem to hang together. Which is why they're putting this result out there, knowing full well that it disagrees with just about everything else. They're hoping that some clever person will spot a mistake, or, failing that, that another experiment will do the same test (there's one in Japan and one in the US), and see if they get the same result….
It'd be deeply, deeply weird, though, not least because the existence of superluminal particles that interact with ordinary matter (as neutrinos do, albeit weakly) opens the door to violations of causality-- effects happening before the things that caused them, and that sort of thing. This wouldn't be a big loophole-- the speed difference is tiny, and neutrinos interact extremely weakly-- but it's the kind of philosophical problem that would really bother a lot of people.
So, if you had money to bet on it, bet that this result is wrong. But these guys aren't complete chumps, and if something is wrong with their experiment, it's something pretty subtle, because they've checked all the obvious problem areas carefully.
