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Question: Can the acceleration of gravity exceed the speed of light?

(Posted by: Andrew on 2010-03-09 18:06:46)

I don't understand how the acceleration of gravity is limited by the speed of light. If it holds true that the closer you get to the center of an object, the greater the acceleration of gravity towards it becomes, then wouldn't the acceleration of gravity be greater than that of light on the inside of a black holes' event horizon, seeing as the event horizon is the point at which g=c and the black holes' center can still be billions of miles away? I mean, think about it: Why would g simply flatline when it gets to the event horizon? g has been getting greater and greater as you approach the event horizon, so why would it simply become constant the rest of the way to the center of the black hole?

Posted by: Mark V on 2010-03-09, 18:13:59

Because at the event horizon, it's not so much that velocity hits a wall, it's that within the confining event horizon, gravity has distorted space to a level at which our normal concept of space with evenly stationed geometric points in nice grids no longer applies. In fact, space had been warping long before you got to the event horizon. When you passed it, you essentially entered a realm where, according to general relativity, the entire concept of space-time itself no longer applies. Even perception no longer matters -- with you inside the event horizon, I'd see you instantly blip out of existence. But you looking out at me, it would seem to take a literal forever to fall into the center of the black hole. So that's why. Space-time has no further meaning, and even matter and energy itself is right on the edge, so the speed of light no longer has any important meaning.