Why can gravity escape a black hole but not light?

Asked by: Oisin Peavoy, Dublin

To escape from within a black hole requires faster than light speeds, but according to Einstein’s theory of gravity, General Relativity, gravity is the distortion of space and time caused by the presence of mass. As such, gravity doesn’t escape from within the interior of the black hole: it’s simply caused by the hole’s presence. If black holes collide, however, the space-time surrounding them responds by producing ripples known as gravitational waves; but again they aren’t ‘escaping’ from within the black holes.

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