October 27, 2016
photon deflection, solar deflection, general relativity
It has been held that the total solar deflection of light could only be derived correctly by Einstein’s general theory of relativity. This paper provides a new classical derivation for the total gravitational deflection of light as a photon passes by the Sun. Newton, Cavendish, Einstein and others discussed or calculated how gravity may bend the paths of light. In particular, von Soldner published an incomplete classical derivation to predict a solar deflection that was half of the later observed value, since he assumed a light wave was deflected by a stationary Sun. Einstein’s earliest derivation used his equivalence principle of a homogeneous gravity field and a constant dynamical acceleration, which predicted half of the observed solar deflection angle, because he was then unaware of all the first-order space-time contributions. Einstein’s general relativity theory predicted the full solar deflection. Assuming the photon has a mass via Einstein’s mass-energy equation, this classical derivation uses Newton’s mechanical laws and his law of gravitation for the photon’s and the Sun’s hyperbolic paths about their mutual barycenter. Both the Sun and photon deflect each other about their barycenter with an infinite lever. This Newtonian derivation obtains the prediction of 1.75" against the celestial sphere for the full gravitational deflection of light relative to the Sun.