Figure 13

Figure 13: Instantaneous wave fronts of the light cone in the Schwarzschild spacetime. This picture shows intersections of the light cone in Figure 12 with hypersurfaces t = constant for four t-values, with t1 > t2 > t3 > t4. The instantaneous wave fronts wrap around the horizon and, after reaching the first caustic, have two caustic points each. If one goes further back in time than shown in the picture, the wave fronts another time wrap around the horizon, reach the second caustic, and now have four caustic points each, and so on. In comparison to Figure 12, the representation in terms of instantaneous wave fronts has the advantage that all three spatial dimensions are shown.