Is it possible that the detected neutrinos actually travelled less distance than the direct path from the source to the detector? I know neutrinos are known for being able to pass through matter with little interaction, but the fact that they can be detected means they will sometimes produce an interaction.
There is some serious speculation that one of the reasons that gravity is so weak (under a quantum view of gravity) is that gravitons are tunneling through dimensions that are too small for most particles to go through, and that neutrinos are doing this, too, and the path is slightly shorter than what you would measure macroscopically.
It doesn't matter much overall, though, because it's the signal velocity that is important. If this be a real effect, then the value of
c would have to be revised upward (which, in SI, would mean that the meter would have to be slightly longer, because
c is given by a constant and the meter is defined with respect to
c and a second). This would mean that if you calculated the distance using the revised definition of the meter, it would be long enough.
So .. what if a neutrino is occassionally absorbed by an atom or particle within the earth and re-emitted? Due to quantum effects, can the time between absorbtion and re-emission be less than the time it would take light to travel the distance from where the particle was absorbed then re-emitted? Could a serious of "quantum leaps" or tunnelling explain the time difference?
I've always found the absorption/re-emission metaphor a bit on the quasi-classical side, and I find it better to think in terms of QED, where the maximum probability path is wiggly and therefore a bit longer. Anyway, the result is the same, and yes, this happens. When a particle goes faster than the signal velocity of light in a medium, then you get Cherenkov radiation. I don't know how they are detecting the neutrinos, but one of the ways is to have them pass through a medium in which the signal speed of light is slower and measure the Cherenkov radiation.
Still, however, under relativity the signal speed would have to be less than
c, Not that people call
c the speed of light in a vacuum, but a vacuum isn't empty. It's boiling with short-lived particles, and it's been known for some time that when some of these particles are removed (as with Casimir plates), light goes just a hair faster than in an ordinary vacuum. This would mean that our measurements to date of
c are just a hair too low, which I could believe.
As I've pointed out, actually violating relativity would call the GPS measurements into question, because they rely on relativity. However, some drifting of GPS has been observed, and this is normally corrected by signals from the ground. There has been some speculation about whether they may be caused by small irregularities in spacetime. This wouldn't violate relativity; it would just mean that we don't have a full understanding of all the sources of energy/momentum.
