How do you really know that the limits to general relativity for strong fields are set inside black holes?

We know this because general relativity is a classical field theory which predicts that under certain conditions, infinities will occur...called singularities. Here is a version of what happens to space near a blackhole based on the mathematics first discovered in 1921 by the Nobel prize-winner Alvar Gullstrand, and independently by the French mathematician and politician Paul Painlevé. (credit: Univ. Colorado). It emphasizes a concept called collapsing space. Any objects trapped in this space will literally be dragged through the event horizon and crushed at the Singularity.

All known singularities in the theory seem to be hidden behind event horizons. At these locations, space-time curvature defined by the magnitude of the so-called Riemann Tensor, goes to infinity as the radius of the system goes to zero. It is expected that a make-over of general relativity by a fully quantum mechanical field theory (Superstrings, M-Theory, etc) will remove these singularities and replace them by some as yet undefined quantum condition, such as the finite graininess of space-time itself at the Planck Scale.

Return to Dr. Odenwald's Gravity page at the Astronomy Cafe Blog.