All these different observers' characterization of the events can be related and a consistent picture emerges. Another interesting thing to consider is the effect of spatial curvature. As we emphasized, it is the curvature at a point of a spacetime which is the real indicator of a permanent gravitational field. For the Schwarzschild spacetime given above, the curvature can be shown to go as Thus at the Schwarzschild radius the curvature is finite. Such a point is called a singularity and its existence in a spacetime is bad news.
Nothing is well-defined at such a point.
If nature makes singularities which possess no event horizon, then the singular point would be visible. Since all known laws of nature would break down there, it is not even clear that we would have a universe which is predictable. This is because with naked singularities sitting around and visible, there is no predicting what would emerge from such points. The conjecture is that black holes only form with event horizons. The problem is that this has not been proved to be true.