BBC - Bang Goes the Theory - Ask Yan - What is at the centre of a black hole?

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What is at the centre of a black hole?

Asked by Matt from Dover, 8 September 2009

(The answers below are the opinions of the authors.)

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Robert Flack University College London

Explosion at the centre of the black hole Sagittarius A (credit: NASA-MSFC)

Einstein's theory of gravity, general relativity, predicts that the centre of a black hole is what is known as a singularity. This is a place where matter is crushed so much that saying it has length, height and width is meaningless. Therefore the object will have infinite density.

What does this mean? We don't know. Einstein's theory can't handle infinite densities, so we know the theory has to be wrong. The truth must be a deeper and more general theory, but we don't yet know what that theory is, so we can't say for sure what's at the centre because we certainly can't go there to look. We also can't say what the Universe was like at the very beginning, either.

Despite a suggestion from one of the Beacons contributors, while we can't rule the possibility out, it's probably NOT Elvis.

- Answered by Robert Flack, 17th September 2009

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Ask Yan - What is at the centre of a black hole?

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