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Physics
Special and General Relativity
Where does the energy of gravity come from?
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[QUOTE="Feynstein100, post: 6852518, member: 660690"] I think that's what the OP was referring to. Had the earth not been there, the water wouldn't have any gravitational potential energy. Imagine an object outside the earth's gravitational field. It doesn't have any energy. But place it just inside the field and it now gains kinetic energy which it didn't have before. Ah but wait. You have to move it to get it inside the field and in doing so, you give it kinetic energy. Still, it does speed up once it enters the field (assuming it gets closer to the earth), meaning there is a net gain of energy. And assuming conservation of energy holds true, this extra energy has to come from somewhere, in this case the earth's gravitational field. One possible resolution to this problem is to say that the earth's gravitational field extends to infinity and thus the object was never outside it, and always had potential energy. However, this feels like cheating, and I can't help but wonder if there's a better resolution. [/QUOTE]
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Physics
Special and General Relativity
Where does the energy of gravity come from?
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