Is there proof gravity can not be a energy source?

[pinobot]

Of course the sun is the source of the energy but the sun lasts for billions of year, how long does something have to last to be able to be called perpetual motion. If you wait long enough eventually all atoms will fall apart and nothing is perpetual.   

[Omnibus]

Confusion and incompetens @exnihiloest calls science. What is there to refute when confusion in @exnihiloest is so blatant, as I already explained?

[exnihiloest]

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Does that make gravity Energy ? - No, it is an acceleration that needs a mass to be raised by expending Energy [Input Energy] from something else before it can give back that same Energy [Output Energy].
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Hi Fletcher. I agree. Nevertheless there is an exchange of energy: the potential energy is stored in the gravitational field or recovered from it. This is not obvious because we always think about objects whose mass (and gravitational field) can be neglected when comparing to the mass of the earth.

This becomes obvious when we think of bodies of equal mass.
Suppose the universe with two identical planets far from one each other. Their gravitational field fills the whole space. Now they are attracted and accelerate toward one each other. When they are near from one each other, the gravitational field at about mid distance between them, is reduced or null because their gravity is of opposite direction. But at the same distance from each planet, it was strong when they were at their start point.

Thus:
At the start point, at near distance from the planets, there was a strong gravity field.
At the end point, in some areas of space there is a reduced field, even a null field (between the planets).
And energy has been obtained.
We can deduce from this case and from the analogy with electric or magnetic fields and their energy density, that the energy is conserved and has been exchanged between the field and the work done to move the bodies.
It is easy to calculate that the energy density of the gravitational field is g²/(8*pi*G), by the same methode as calculating the energy density of the electric field (1/2*epsilon0*E²) from the work to move between different potentials.

In other words the potential energy of bodies depends on the topology of the field in which they are placed. When they move, the field topology changes. When the movement produces energy, the field is globally lowered, what can be verified by integrating its energy density over the whole space:  the quantity of energy that it has lost is the same as the work which has been gained.
This applies in the context of Newton mechanics, not GR.

[Omnibus]

Hi Fletcher. I agree. Nevertheless there is an exchange of energy: the potential energy is stored in the gravitational field or recovered from it. This is not obvious because we always think about objects whose mass (and gravitational field) can be neglected when comparing to the mass of the earth.

This becomes obvious when we think of bodies of equal mass.
Suppose the universe with two identical planets far from one each other. Their gravitational field fills the whole space. Now they are attracted and accelerate toward one each other. When they are near from one each other, the gravitational field at about mid distance between them, is reduced or null because their gravity is of opposite direction. But at the same distance from each planet, it was strong when they were at their start point.

Thus:
At the start point, at near distance from the planets, there was a strong gravity field.
At the end point, in some areas of space there is a reduced field, even a null field (between the planets).
And energy has been obtained.
We can deduce from this case and from the analogy with electric or magnetic fields and their energy density, that the energy is conserved and has been exchanged between the field and the work done to move the bodies.
It is easy to calculate that the energy density of the gravitational field is g²/(8*pi*G), by the same methode as calculating the energy density of the electric field (1/2*epsilon0*E²) from the work to move between different potentials.

In other words the potential energy of bodies depends on the topology of the field in which they are placed. When they move, the field topology changes. When the movement produces energy, the field is globally lowered, what can be verified by integrating its energy density over the whole space:  the quantity of energy that it has lost is the same as the work which has been gained.
This applies in the context of Newton mechanics, not GR.

Another piece of total crap. The sorry individual @exnihioest will not stop spewing it, evidently. The gibberish that element is cluttering the thread with has to be nipped in the bud.

There's absolutely no evidence (and there can never be because of the very essence of the concept of fields)  of exchanging energy between bodies at rest with each other neither there is evidence for exchanging energy between stationary withe respect to each other electric charges. Like I said, all these formuli regarding electric and magnetic field are only concerning the potential to do work (consider a charged capacitor) and in no way prove that gravitational, electric or magnetic fields are energy sources. Like I said, it is absolutely not true that there's any exhausting of gravity acting between two stationary bodies of the same size. To assert the opposite is as unscientific as to claim that pigs can fly. As for the gravity formula give, that must be rejected out of hand because it has been "derived" at by one of the most non-scientific bs science has ever had to deal with.

[exnihiloest]

Of course the sun is the source of the energy but the sun lasts for billions of year, how long does something have to last to be able to be called perpetual motion. If you wait long enough eventually all atoms will fall apart and nothing is perpetual.

I agree. The sun energy would be enough for humans if we could get it easily.
2/3 of the earth are oceans, so the surface of water that can be evaporated is enormous.
But if we want directly use the sun energy, we have to cover vast surfaces of the earth with panels. In the best case, the sun provides about 1KW/m². We must divide by 2 due to the alternating day/night. We must divide again by 1 to 1.5 depending on the regions, due to weather conditions. We finally must divide by 3 to 6 due to the solar panel efficiency. Therefore it is not satisfying to cover thousands of Km² of earth to get energy. It would be possible in space, but not now because of terrible technological problems.