OT:Tempted to get this book

[Renegade 13]

aiken said:
Slowed light is virtual phenomenon. Once photon from light ray collides with atoms of medium it transfers its energy to atom and disappears, but atom goes to hugher energy state. After some time atom re-emits photon with similar wavelenght in the same (if medium has no lens ability) or different direction and then atom goes back to initial energy state. This effect will occur many times until photon leaves meduim. Since cycle of "absorbtion-reemission" is not instant, it gives effect of "slowed light".

edit: note, that it's a very primitive explanation which assumes that photon bahaves itself as a particle. But in real world it also behave itself as a wave. And things become slightly more complicated. But the principle remains the same.

Ok, that makes sense. Based on your explanation, the speed of light in a vacuum is the "fastest" light can travel through any known medium, since there is virtually nothing to "slow" the light wave/particle. Therefore, the speed of light in a vacuum is the "fastest" anything can travel, as far as we know (disregarding certain quantum effects if my memory serves me well). I always knew that light behaved (under certain circumstances) as a particle and/or a wave. However, what significance does this have?