You need energy to produce a force that compensates gravity. So if you apply that force for a huge amount of time, will gravity ever be depleted?
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What you’re talking about is force. But force doesn’t to *work* unless it moves a distance. and *work* is energy. If there’s no movement, there’s no work done, and thus no *energy.*
It requires a certain amount of *energy* to move two objects in the opposite direction of their gravitational pull (pull them “apart”). If you allow those two objects to return to their original positions, they will “release” the same amount of energy which was consumed to separate them in the first place.
You’re assumption seems to be that, in order to *maintain* a force, *energy* is being *consumed (*in the same way you get tired if you push on a wall for long enough)*.* this is the disconnect. Energy *will ONLY* be consumed or released when that force begins to move, and do *work.*
In the case of your body getting tired pushing on a wall, or say, holding a book up in place, your body *is* doing work – but not on the wall, or book. This is because your muscles actually are moving on a microscopic level. you can never actually stand perfectly still, and your muscles and skeletal structure sort of “ripples”. This ends up consuming energy and rejecting it in the form of heat for the most part. There is also some chemical reactions at play where energy plays a role in the reaction but i’m not well versed enough here.
By analogy, if you had a pressurized cylinder with a piston, and allowed that piston to press on the wall with the pressure of the cylinder but the wall did not move – that piston would continue applying force forever without any additional energy input. this is also true if you replace the gas cylinder with just a spring.
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