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If something falls into a black hole, but has not yet hit the singularity in the center, can we (outside of the black hole) feel its gravity? On the one hand, I've learned that there's no distance limit to gravity and that everything in the universe feels the gravity of everything else. On the other hand, we would be able to measure the gravitational field of the thing and thus figure out where in the black hole it is, which contradicts the idea that no information can escape a black hole.

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  • $\begingroup$ I don't think there's an answer to this. Primarily because we can never actually observe something actually fall into a black hole. From our perspective, the gravitational time dilation means we can't observe matter actually crossing the event horizon, no matter how long we watch. And by watch I mean do anything that involves observing this system including physically seeing it or measuring gravitational effects. $\endgroup$ – zephyr Nov 16 '16 at 19:13
  • $\begingroup$ But if gravitational force travels at the speed of light won't that also diminish - ie suffer the equivalent of a relativistic red shift - so the answer to the question is essentially "no"? $\endgroup$ – adrianmcmenamin Nov 16 '16 at 19:51
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    $\begingroup$ Lets say you have a very sensitive piece of equipment in orbit (geosynchronous), and you want to measure the gravitational change of a rock falling through the air towards Earth, as the rock moves away from your equipment (at 9.8 m/s^2) the Earth moves towards the rock at an infinitesimally small rate and the center of mass doesn't change. Mathematically, could that be detected with very finely calibrated equipment? I don't know, but I think, start there and work backwards to the question on black holes. $\endgroup$ – userLTK Nov 16 '16 at 20:40
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Gravity, according to the majority of published and non-published scientists, is able to propagate information from one point to another at the speed of light. This means that as soon as any massive body "physically" interacts with a black hole (enters the Schwartzchild radius) there is no longer a way for anything outside of the black hole to know anything else regarding the status of the body. Therefore the new addition to the black hole simply becomes part of the system and can no longer be considered a separate entity. The body's gravity becomes that of the black hole's.

So... No

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