Galilean Invariance and Mach's Principle
Galileo’s “Principle of Relativity” omits any consideration of an absolute frame of reference with respect to which motion is measured. Kinetic energy would appear to be a relative quantity whose magnitude depends on the chosen frame of reference, or in the case of its centrifugal force derivative, depends on which polar origin is chosen. The magnitude of any physical interaction involving two bodies is only ever dependent on their relative velocity, and there seems to be no way of exposing the existence of any special frame of reference with respect to which linear kinetic energy is an absolute physical quantity. The fact of centrifugal force however does indicate that such a frame of reference must exist, and that this frame appears to be embedded in a medium that is in a state of zero rotation relative to the fixed background stars. Rotation relative to the fixed background stars induces centrifugal force, which suggests that kinetic energy is indeed an absolute physical quantity that is induced by the interaction of a moving body with a physical medium which pervades all of space. In this article it will be proposed that the physical medium for the propagation of light is also the cause of kinetic energy and centrifugal force, and we will be reminded that Maxwell’s equations are formulated specifically with this medium as the standard of rest. Important questions relating to the motion of this luminiferous medium relative to the planets and the stars will then be discussed.