Limitations of Einstein's equivalence principle and the mass-charge repulsive force

Although Einstein insisted on the fundamental importance of his equivalence principle, many did not understand its solid foundation in mathematics and physics and had mistaken his principle to be the same as Pauli's version or the 1911 preliminary assumption of equivalence. It is shown that the limitation of Einstein's equivalence principle is revealed by the Reissner-Nordstrom metric of a charged particle because this metric necessarily implied the existence of a charge-mass repulsive force. For two pointlike particles having a relative distance r, the repulsive force would be mq(2)/r(3) where m and q are, respectively, the mass of one particle and the charge of the other. Thus, the equation of motion as the geodesic equation+the Lorentz force is inadequate, and a unification of gravitation and electromagnetism is necessary. However, if one extends the equivalence principle to a five-dimensional space, the repulsive force would be included in a five-dimensional relativity. Experimental verification of this fifth force is proposed, and it would provide evidence for Einstein's belief, the conditional validity of E=mc(2). (c) 2008 Physics Essays Publication.