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prase comments on Particles break light-speed limit? - Less Wrong
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What do you mean by that light is subluminal? Literally it means that light travels slower than light, which is probably not the intended meaning.
I suspect he means that light maybe travels slightly slower than the constant c used in relativity. Maybe photons actually have a really tiny rest-mass. Maybe our measurements of the speed of light are all in non-perfect vacuum which makes it slow down a little bit.
If they had tiny mass, we would observe variance in measured values of c, since less energetic photons would move slower. Measurements of c have relative precision of at least 10^-7 and no dependence on energy has been observed in the vacuum. Therefore the measured speed of light doesn't differ from the relativistic c more than by 10^-7. The relative difference which is reported in the neutrinost seems to be 10^-5.
Kloth answerd as I would.
By the way, electrons in water can be faster than photons in water. No big surprise maybe, if this hapens with neutrinos and photons in a (near) vacuum.
Light can move more slowly while not in a vacuum, maybe this light was held up by something. That said, I don't understand the paper well enough to tell if they are directly racing the neutrinos against some actual light, or if they're just comparing it to an earlier mesurement.
I don't know whether this guy knows what he's talking about, but it sounds plausible:
Steven Sudit:
There have been no indications that one can transmit information FTL using the Casimir effect, the work he mentions was on quantum tunneling time, which is a different beast.
That doesn't work. They didn't race the neutrinos against a light beam. They measured the distance to the detector using sensitive GPS.
Are they THAT sensitive? Possibly not.
In order for this to be from an error in measurement you need to be a few meters off (18 meters if that's the only problem). There are standard GPS techniques and surveying techniques which can be used to get very precise values. They state in the paper and elsewhere that they are confident to around 30 cm. Differential GPS can have accuracy down to about 10-15 cm, and careful averaging of standard GPS can get you in the range of 20 cm, so this isn't at all implausible but it is still a definite potential source of error.
A more plausible issue is that since parts of the detectors are underground they didn't actively use GPS for those parts. But even then, a multiple meter error seems unlikely, and 18 meters is a lot. It is possible that there's a combination of errors all going in the same direction, say a meter error in the distance, a small error in the clock calibration, etc. And all of that add up even as each error remains small enough that it is difficult to detect. But they've been looking at things really closely so one would then think that at least one of the errors would turn up.