--Changshen (talk) 04:42, 27 September 2011 (UTC) Assume that the "naked" speed of photon is unlimited and is infinite in a "naked" vacuum, a truly free space-time. The "naked" photon speed reduced to light speed C is because the photon generates ghost particles and it interacts with those ghost particles. The fast the speed of the photon is, the more the ghost particles it generates. They reaches a balance (re-normalized speed). The interaction among photon and its ghost particles drag and slows down the speed of the photon
That is the theoretical speed of photon has no limit and can go to infinite in a “truly” free space-time which means no ghost particles will be created by the photon itself, and no any other ghost particles or real particles, and no quantum fluctuation. But the photon cannot travel with that unlimited speed because it very soon emits ghost particles which, in turns, interacts with the photon itself (coupling with those ghost particles), that self interaction drags the photon and slows down its speed to a limited speed until its own ghost particles no longer posts drag force to the photon itself (the naked photon). That means the rate of ghost particles generation and the strength of interaction with those self generated ghost particles decide the speed of the photon in the real space-time, and reaches the re-normalized maximum speed C.
For neutrinos’ speed, if its speed is faster than C, we can argue that the neutrinos have weaker interaction (smaller coupling ) with the ghost particles and real particles than photon does and it does not generate many ghost particles as photon does, either.