  Einstein utilized Lorentz invariance from Maxwell's equations to modify
mechanical laws and establish the special theory of relativity. Similarly, we
may have a different theory if there exists another covariance of Maxwell's
equations. In this paper, we find such a new transformation where Maxwell's
equations are still unchanged. Consequently, Veselago's metamaterial and other
systems have negative phase velocities without double negative permittivity and
permeability can be described by a unified theory. People are interested in the
application of metamaterials and negative phase velocities but do not
appreciate the magnitude and significance to the spacetime conception of modern
physics and philosophy.
