Is the speed of light invariant or covariant?

Abstract

According to the theory of ether light propagates with constant speed c with respect to the absolute reference frame and with respect to any other reference frame the speed of light is covariant. According to the theory of special relativity the speed of light is invariant with respect to any reference frame. The new theory of reference frames gives a different answer to this question with the consideration of two speeds of light: the physical speed and the relativistic speed. After considering a few negative aspects of the two main theories a few fundamentals of the new theory are expounded.