Is there proof gravity can not be a energy source?

[Omnibus]

Assuming zero friction, a car going up and down between two hills will still not make a self sustaining overunity machine.  At best, you will have perpetual motion - unity.  But not overunity.

So what is the point of this alleged CoE violation if it can never produce excess energy?  And to be clear, I do not see how there can be any CoE violation here whatsoever.  Potential energy is converted to kinetic, then back to exactly the same amount of potential.  Energy is perfectly conserved.

No, like I said, no self-sustaining machine can be made out of this. But not being able to make a self-sustaining machine is not a criterion for whether or not CoE can be violated. CoE in this case is violated because the integral of the work done in a closed loop is not zero as it should be if CoE is obeyed. And, no, in this case potential energy is not converted into kinetic on its way up. The kinetic energy at the top of the hill is in addition to the potential energy the car has there. So at the top of the hill the car has (potential energy + kinetic energy1) while at the bottom of the hill, when the car returns spontaneously that potential energy only is converted into potential energy2. So as far as the car is concerned we have: potential energy = kinetic energy2 < (potential energy + kinetic energy1). CoE is violated. If CoE were not violated we would have potential energy = kinetic energy2 = (potential energy + kinetic energy1) which is not the case.

[exnihiloest]

...
Gravity are by definition not acceleration
...

You are wrong against Einstein. All observations done until now proved he was right.
If you deny the equivalence principle, you will have to give solid evidence!

"The gravity of Earth, denoted g, refers to the acceleration that the Earth imparts to objects on or near its surface."
http://en.wikipedia.org/wiki/Gravity_of_Earth

http://roberta.tevlin.ca/Rel/GR%20I/GR%20I.ppt

[exnihiloest]

Assuming zero friction, a car going up and down between two hills will still not make a self sustaining overunity machine.  At best, you will have perpetual motion - unity.  But not overunity.

So what is the point of this alleged CoE violation if it can never produce excess energy?  And to be clear, I do not see how there can be any CoE violation here whatsoever.  Potential energy is converted to kinetic, then back to exactly the same amount of potential.  Energy is perfectly conserved.

Hi utilitarian, you are perfectly right. There is no CoE violation in a closed loop or in any path in a closed sytem in which the start and end points are at same potential.

Now a question remains. When the car is down the hill and the driver brakes and stops the car, the potential energy it had at the start point, has been converted in heat, finally radiated in the environment.
"Potential" energy doesn't mean "fictive" energy. The potential energy was real because the car used it. Thus the question is: where was stored the potential energy of the car at its start point? The only plausible answer is "in the gravity field of massive bodies" (car and earth). When the car is down the hill, the gravity field pattern has changed, resulting in less energy in the field.
The energy density of a gravity field, which can be calculated like the energy density of an electric field (1/2*epsilon0*E²) is g²/(8*pi*G), which is an enormous quantity. Its order of magnitude seems to be rather compatible with the weak change of the gravity field due to the "fall" of the car and supposedly equal to the difference of potential energy of the car between start and arrival points. By modeling the car as a sphere, adding its own gravity field to that of the earth in order to obtain the exact g field, and integrating the density energy all over the space, we should retrieve the potential energy that the car used (I think I could do that, but it is a bit tedious...    ).

[Low-Q]

You are wrong against Einstein. All observations done until now proved he was right.
If you deny the equivalence principle, you will have to give solid evidence!

"The gravity of Earth, denoted g, refers to the acceleration that the Earth imparts to objects on or near its surface."
http://en.wikipedia.org/wiki/Gravity_of_Earth

http://roberta.tevlin.ca/Rel/GR%20I/GR%20I.ppt

OK, I was wrong about the definition. Anyway, the acceleration are constant for any object. The relative relationship between two objects with same acceleration are trivial, and can therfor not exchange energy more in one direction than the other without energy input - in order to achieve more acceleration to one of the two objects. Gravity are conservative. If gravity is acceleration, this acceleration is also conservative. Therfor gravity is not the same as energy, because energy is not conservative, but a process to equalize two different potentials. In order to achieve two different potentials, energy must be applied. Gravity cannot do this alone, because the acceleration, or gravity, are applied equally already between those two objects.

Vidar

[Omnibus]

You are wrong against Einstein. All observations done until now proved he was right.
If you deny the equivalence principle, you will have to give solid evidence!

"The gravity of Earth, denoted g, refers to the acceleration that the Earth imparts to objects on or near its surface."
http://en.wikipedia.org/wiki/Gravity_of_Earth

http://roberta.tevlin.ca/Rel/GR%20I/GR%20I.ppt

I am not wrong about Einstein because his "theory" fails before considering experimental evidence because sid "theory" internally contradictory. Proposals based on internal contradictions are called nonsense, not theorues. Nonsense cannot be the subject to examination by experiments whatsoever. In particular nonsense such said "theory" has nothing to do with the equivalence principle or with any principle for that matter. Nonsense is rejected out of hand without any consideration of any kind.