# Special & General Relativity Questions and Answers

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

Because general relativity is a classical field theory which predicts that under certain conditions, infinities will occur...called singularities. 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 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.

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All answers are provided by Dr. Sten Odenwald (Raytheon STX) for the NASA Astronomy Cafe, part of the NASA Education and Public Outreach program.