Foundations of Physics Vol. 38, pp. 293-300 (2008).
The original publication is available at www.springerlink.com
http://dx.doi.org/10.1007/s10701-008-9209-1
Charge, like mass in Newtonian mechanics, is an irreducible element of electromagnetic theory that must be introduced ab initio. Its origin is not properly a part of the theory. Fields are then defined in terms of forces on either masses–in the case of Newtonian mechanics, or charges in the case of electromagnetism. General Relativity changed our way of thinking about the gravitational field by replacing the concept of a force field with the curvature of space-time. Mass, however, remained an irreducible element. It is shown here that the Reissner-Nordstrom solution to the Einstein field equations tells us that charge, like mass, has a unique space-time signature.