The speed of photons in a vacuum IS the speed of light. According to special relativity, it is the maximum speed at which particles can propagate. A consequence of special relativity is that time stops for a frame of reference traveling at c.
To the best of my knowledge, there are a few quantum experiments that appear to contradict c as the universe's speed limit. However, it is NOT due to particles propagating at >c; instead, it has to do with transfer of information at speeds greater than the speed of light.
The first contradiction is the Pauli Exclusion Principle. When an electron in an orbital changes spin, the other electron in the orbital instantaneously changes its spin to conform to the rule (no two electrons with the same quantum numbers can exist in one orbital). This is in direct violation of special relativity.
The second is an actual experiment, where a "pair" of particles (electrons, I think) go off in opposite directions. A magnet changes one of the electron's spin value midflight, and the spins od the two particles are recorded. They are always opposite. Thus, the electron "transfers" information to its paired electron instantaneously to its partner, regardless of spatial distances.
Slashdot Mirror
The speed of photons in a vacuum IS the speed of light. According to special relativity, it is the maximum speed at which particles can propagate. A consequence of special relativity is that time stops for a frame of reference traveling at c. To the best of my knowledge, there are a few quantum experiments that appear to contradict c as the universe's speed limit. However, it is NOT due to particles propagating at >c; instead, it has to do with transfer of information at speeds greater than the speed of light. The first contradiction is the Pauli Exclusion Principle. When an electron in an orbital changes spin, the other electron in the orbital instantaneously changes its spin to conform to the rule (no two electrons with the same quantum numbers can exist in one orbital). This is in direct violation of special relativity. The second is an actual experiment, where a "pair" of particles (electrons, I think) go off in opposite directions. A magnet changes one of the electron's spin value midflight, and the spins od the two particles are recorded. They are always opposite. Thus, the electron "transfers" information to its paired electron instantaneously to its partner, regardless of spatial distances.