Q: In the NEC “faster than light” experiment, did they really make something go faster than light?
The original question was: I was reading an article by Lijun Wang the experiment I think is called the NEC experiment. Basically what the guy does is speed up light so that it goes faster than the than the speed of light. No physical objecttravels faster than light, and yet the experiment is real. This is pretty tricky, but it comes down to a distinction between “phase velocity” (light speed, “c”) and “ group velocity” (depends on the medium). For comparison, the group velocity of light in water differs from the phase velocity by less than 1% (which is different from 31,000%).