I'm kind of expecting that the reason may either be completely mundane, or even if it's something that requires a change in our understanding of physics, it's something else than FTL travel of particles being possible. After all, the measured speed is only 0.0000002% above c. This might indicate that it's a mundane error.
Some possibilities come to mind. It could be that:
- regardless of the seemingly high care taken to measure the time very accurately, there was some kind of really tiny calibration error somewhere.
- the distance between the two measurement points was measured just a tiny bit wrong (after all, getting the distance wrong by 0.0000002% doesn't sound like an unlikely cause).
- there's a physical factor, still completely within current knowledge of physics, that was not taken fully into account, such as the curvature of spacetime near a gravity well (such as the Earth is). I wonder if this might be somehow related to the so-called
flyby anomaly.
- there's an unknown factor affecting the curvature of spacetime, and hence the distances between points, such as some kind of dark matter.
- the equations for spacetime curvature calculations need adjusting for an unknown reason. (OTOH this and the two previous are unlikely because it would affect all measurements of c, including traditional measurements of light itself.)
- an unknown or dismissed quantum effect is in play, making it appear as if the particle traveled faster than c, when in fact it didn't.
