In some media, mass-carrying particles can go faster than light:
Cherenkov radiation, ... is electromagnetic radiation emitted when a charged particle... passes through a dielectric medium at a speed greater than the phase velocity of light in that medium
How does this happen? I would imagine that light faces the least resistance to motion and that other charged mass-carriers have more stuff to impede their speed.
Why are the particles allowed to exceed the speed of light for other media when they are not allowed to in a vacuum?
Answer
Cherenkov radiation is generated by charged particles which are faster than the local speed of light in an optical medium, which is always lower than the speed of light in vacuum. So if the local speed of light in an optical medium is given by c_medium = c_vacuum/n, where n is the refractive index, a particle with c>v>c_medium can generate Cherenkov radiation, even though it is slower than the actual speed of light in vacuum. Such particles can be found in cosmic rays and are made copiously in our accelerator facilities, where Cherenkov detectors are used often to detect them. The optical media used in Cherenkov detectors do slow particles down, of course. The Cherenkov light requires energy, which has to come out of the kinetic energy of these relativistic particles. Typically, however, particles can travel several meters, and sometimes many miles trough Cherenkov media before they have lost all of their energy.
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