Action and reaction in the theories of direct interparticle action

Abstract

Newton's third law of motion is examined in the context of the theories of direct interparticle action. In such theories, interactions between particles travel backward and forward in time at speeds not exceeding the speed of light. It is shown that while in the flat spacetime the equality of action and reaction can be clearly demonstrated, the situation is considerably more complicated in the curved spacetime. The phenomenon of gravitational scattering intervenes to destroy the equality of action and reaction. Nevertheless, when gravitation is taken into account, there is no violation of the conservation law of energy and momentum. These results are discussed in the framework of general relativity for the case of the electromagnetic interaction.