Can gravity be focused by large massive objects?
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1$\begingroup$ Gravitational waves and gravity are not the same thing. For example, you can have gravity without any waves in it. Can you please make your title and body agree with each other so that it is clear which you are asking about? $\endgroup$– G. SmithAug 22, 2020 at 2:12
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$\begingroup$ Duplicate physics.stackexchange.com/questions/413995/… physics.stackexchange.com/questions/170410/… $\endgroup$– Árpád SzendreiAug 22, 2020 at 3:21
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Yes. The equivalence principle implies that everything is affected in the same way by gravity, including gravity.
This is true of gravitational waves. It should also be true of the static gravitational field, though I don't remember ever reading about it (or thinking about it) before. Probably, the gravitational attraction of two inline objects is slightly larger than a naive Newtonian calculation would suggest—although it's difficult to say what distances you should plug into the Newtonian formula when making that calculation.
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$\begingroup$ If gravity affects gravity how does gravity escape a black hole? $\endgroup$ Aug 22, 2020 at 3:41
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$\begingroup$ @AdrianHoward I'm suspect you already know this, but gravity the most mysterious of the forces and quite unlike the others in that it appears to be distortions in the fabric of space-time. That means that unlike an EM wave that is either there or its not, the "thing" that causes gravity is always there and is continuous. It can be distorted but not moved or broken. [cont...] $\endgroup$– DKNguyenAug 22, 2020 at 5:32
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$\begingroup$ So if you drag an EM wave into a black hole, it's gone. But if you drag space-time fabric, it continues to pull on more fabric, stretches, and distorts (however you want to visualize it) beyond the black hole. So you can drag fabric into the black hole, but that doesn't leave zero fabric behind. It just stretches and distorts which begets more gravity. So you have gravity affecting gravity and even though it is all being pulled into the black hole, you can still feel the effects of such outside even though nothing really escapes. $\endgroup$– DKNguyenAug 22, 2020 at 5:36
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$\begingroup$ @AdrianHoward Gravity does not “escape” from a black hole - see physics.stackexchange.com/questions/937/… $\endgroup$ Aug 22, 2020 at 7:45
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1$\begingroup$ You are missing my point. If gravity could affect gravity the way it does light then black holes could not exist. $\endgroup$ Aug 22, 2020 at 8:20