# HEP - ASTRO SEMINAR<br>Physical Metric and the Nature of Gravity: Black Holes, Supernovae, Cosmic Rays, Cosmic Acceleration, and All That

A physical metric is defined as one which gives a correct description for observational data without a further coordinate transformation. It is shown that neither the Schwarzschild metric nor the metric described in 1916 by Schwarzschild do give a correct result for time delay experiment by Shapiro et. al. It will be shown that a metric which satisfies the condition that speed of light on the spherical direction is that in vacuum gives a correct result in first order of gravity. Extending this condition to higher order of gravity, one can determine the physical metric exactly. All the metric functions thus obtained are positive definite and exhibits a repulsive force at short distances. The horizon in the sense of vanishing of the speed of light still exists in the radial direction. It is located at 3v3r_{s}/2=2.60 r_{s} , where r_{s}=2GM/c² is the Schwarzschild radius. This radius corresponds to the size of a black hole, as well as the photon radius. The metric can be used to calculate general relativistic predictions in higher order for any process. An interesting case is for the time delay experiment for a binary pulsar for which the accompanying partner is a black hole.