Abraham-Minkowski dilemma concerning the momentum of light within dielectric materials has persisted over 100 years[1]-[2] and conflicting experiments were reported until recently[3]-[4]. We perform a reversed Fizeau experiment to test the compositio
n law of light speeds in media and the result accords with extended Lorentz transformations where the light speed c is changed to c/n. This is a crucial evidence that Minkowskis formulation p=nE/c should be correct although the momentum is not measured directly. By the way, the energy velocity of an electromagnetic field transferred along good conductors may be much faster than c and people have broken the light barrier for a very long time.
