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Name: Jack W Ryan
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Question:
If the gravitational force of a black hole is so strong that not even light can escape, how can the force due to gravity/gravitons escape to affect matter outside the black hole and create the accretion disk that allows us to detect the black hole?



Replies:
In relativity, we no longer think of gravity as a "force". Spacetime in the vicinity of a very compact mass becomes badly distorted. A shell forms around the mass from which nothing can escape. The inside of this shell is what we call the "black hole". Spacetime outside of the shell is also distorted. A mass that is outside of the shell will be subjected to an acceleration toward the center of the shell by the distortion of spacetime. But nothing has "escaped" from the black hole to cause this acceleration. In other words, the concepts that govern our everyday language no longer apply.

J Lu


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