Thursday 11 October 2018

How much energy does lowering an object into a black hole generate?


An object of mass m is slowly lowered into a black hole of mass 1000 m. Is the amount of braking energy larger than $0.6 mc^2$?


Now what if, after lowering the mass close to the event horizon, we wait the black hole to shrink to mass 100 m, by emitting Hawking radiation, and then we lower the mass some more? Is the braking energy of the second lowering process larger than $0.5 mc^2$?


I wonder can we extract more than $E=mc^2$ energy from mass m?



(In this thought experiment we use a wire and a winch, or anything that works)




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