On the Dynamical Relativity Principle and Cosmological Metric

In this paper a novel physical picture of space-time is introduced by means of making a further distinction on the absolute background of space-time and the relative length or duration of base units of space-time. Just based on the existence of the absolute background for space, an explicit dynamical equation which satisfies a moderately general principle of relativity is logically derived under the nonrelativistic framework of classical mechanics. The nature of the inertial force is firstly revealed as the real forces acting on the reference object. Therefore, Einstein's equivalence principle should be abandoned and only the numerical equality between the inertial mass and gravitational mass can be retained. Consequently, the candidate for the standard clock should be changed and an adjusted physical picture for how to convert the gravitational force into a geometric effect on space-time is thereby presented. As for cosmology, it should be emphasized that the observer at the present time on the earth, instead of the comoving observer, is the only true observer. The coordinate time "t" in the cosmological metric is just introduced as the reading number of the observational clock, whose running rate is duplicated from the clock equipped by the observer at the present time on the earth. With this new physical picture of space-time, an extra factor $b(t)$ must be introduced into the cosmological metric to describe the gravitational time dilation effect since the comoving local intrinsic clock will run in a faster and faster rate with the expanding of the universe. In this way, we may obtain a positive value of $\rho+3p$ and avoid the introduction of dark energy in the current universe.