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3
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Controllable faster-than-light phase velocity
The phase velocity of light in a fully ionized plasma is strictly superluminal; see equation 1156 of Fitzpatrick. Like all media in which the speed of light is not $c$, plasmas are dispersive, but the …
51
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Accepted
In superluminal phase velocities, what is it that is traveling faster than light?
Shine a flashlight on a wall. Rotate the flashlight so the illuminated spot moves.
Q: How fast does the spot move?
A: It depends how far away the wall is.
Q: How fast can the spot possibly move?
A: …