Is there proof gravity can not be a energy source?

[Low-Q]

Gravity is an acceleration, not a force. Its energy is stored in the gravity field around the masses, not in the mass: if the mass of a star disappeared, a body placed in its field at a distance d, would be always submitted to the star gravity during a time t=d/c after the event, due to the speed limit c which delays the field collapse at distant locations. Same thing as still receiving light from a far dead star. If the body was at 10 lightyears from the exploded star, it would feel the same gravity during 10 years after the star have disappeared. Bodies can fall in such a gravity field from phantom stars.
This means that gravity can exist without a mass, in the same manner that EM waves still exist without the electric charges that produced them in the past. Therefore energy that can be extracted from a body falling in a gravity field, is really coming from the field; it is a consequence of locality principle.

The force are equivalent to the force provided at an acceleration of 9.81ms^2. Gravity are by definition not acceleration, but we call it gravitational acceleration. Because an object in free fall will accelerate at the given rate when constant force from the gravitational field are applied. Gravity are still a force. Acceleration per definition applies only to the accelerating object in free fall.

Anyway, gravity are not energy. It is constant, conservative, no change. Energy are only applied or released when an object change altitude. The energy applied on its way up, are exact the same as the released energy on its way down. That leaves gravity as a force, and the change in altitude leaves potential energy.

Vidar

[Omnibus]

Although the rest is correct this is incorrect, as I already explained:

The energy applied on its way up, are exact the same as the released energy on its way down.

When a body is lifted at height h it not only has the potential energy mgh due to position but also has kinetic energy (1/2)mv^2 due to the inevitable change of velocity when lifting it.  Now if the motion of the body is stopped at height h and the body is left at rest there the kinetic energy is lost (transformed into other energies, ultimately into heat) and the only energy that can be recovered in completing the loop is mgh. The energy balance is always performed on the energy of the body. Thus, there's violation of CoE even in this simple case.

[spinn_MP]

Although the rest is correct this is incorrect, as I already explained:

When a body is lifted at height h it not only has the potential energy mgh due to position but also has kinetic energy (1/2)mv^2 due to the inevitable change of velocity when lifting it.  Now if the motion of the body is stopped at height h and the body is left at rest there the kinetic energy is lost (transformed into other energies, ultimately into heat) and the only energy that can be recovered in completing the loop is mgh. The energy balance is always performed on the energy of the body. Thus, there's violation of CoE even in this simple case.

Ouch.

So, every time I put a book on the shelf - if I do that quick enough - CoE is violated?
Nice. 

[ResinRat2]

There really is no violation. When a mass is released at the top of a circular path, the only force applied on it is gravity downward.(assuming it is released at rest just past the top of the circle.) This gives the mass momentum up until the bottom of the circle. At that point the momentum begins to fall because gravity is now working against it. The mass will never reach the top of the circle because energy is lost from friction, etc. and the ball will stop, ending all momentum. All energy conserved and accounted for.

Unless energy is added from an outside source to allow the mass to complete the circle, there is no momentum enough to allow that to happen. No violation of CoE. Continual input of energy is needed to keep the motion going. No violation of CoE. The momentum will stop unless energy is continually applied to the mass. No violation again.

Maybe I am not clear. What are the starting parameters of your moving mass that allows it to violate CoE?

[Omnibus]

There really is no violation. When a mass is released at the top of a circular path, the only force applied on it is gravity downward.(assuming it is released at rest just past the top of the circle.) This gives the mass momentum up until the bottom of the circle. At that point the momentum begins to fall because gravity is now working against it. The mass will never reach the top of the circle because energy is lost from friction, etc. and the ball will stop, ending all momentum. All energy conserved and accounted for.

Unless energy is added from an outside source to allow the mass to complete the circle, there is no momentum enough to allow that to happen. No violation of CoE. Continual input of energy is needed to keep the motion going. No violation of CoE. The momentum will stop unless energy is continually applied to the mass. No violation again.

Maybe I am not clear. What are the starting parameters of your moving mass that allows it to violate CoE?

We're not talking here about circular motion (although violation of CoE can occur there as well). The violation at hand is when you have a body lying on the floor then lifted to height h, and then let it go on its own from height h back to the floor.