Light bending and perihelion precession: A unified approach

The standard General Relativity results for precession of particle orbits a nd for bending of null rays are derived as special cases of perturbation of a:quantity that is conserved in Newtonian physics, the Runge-Lenz vector. First, this method is applied to give a derivation of these General Relativ ity effects fdr the case of the spherically symmetric Schwarzschild geometr y. Then the lowest order correction due to an angular momentum of the centr al body is considered. The results obtained are well known, but the method used is rather more efficient than that found in the standard texts, and it provides a goad occasion to use the Runge-Lenz vector: beyond its standard applications in Newtonian physics. (C) 1999 American Association of Physic s Teachers.