Past-Future Asymmetry of the Gravitational Field of a Point Particle

The analytic extension of the Schwarzschild exterior solution is given in a closed form valid throughout empty space-time and possessing no irregularities except that at the origin. The gravitational field of a spherical point particle is then seen not to be invariant under time reversal for any admissible choice of time coordinate. The Schwarzschild surface r=2mis not a singularity but acts as a perfect unidirectional membrane: causal...