Here are some lay-person's thoughts about gravitational potential energy. Some kicking about would be of value.
Consider a rock lying on the ground. If you pick up that rock, then let go of it, it will fall back to the ground. Your action in picking it up has involved a transfer of energy. Some energy from your muscles has been converted into gravitational potential energy as you raise the rock. If, when you have lifted the rock, you place it on a shelf, and let go of it, it will not fall, but it will still have the energy you transferred to it, still in the form of potential energy.
Obviously, if it is pushed off the shelf it will fall back to the ground. The argument here seems to be that the energy you put into the rock as you lift it equals the energy that would be necessary for gravity to bring it back to the Earth’s surface, so there is no net expenditure of energy. Gravity does not expend energy, therefore gravity is not a force.
Could this explain how gravity seems to work without any apparent energy source? A little thought about this situation must raise some doubts. For example, if the attraction of gravity is directly related to the amount of energy put into the rock you are lifting, why does gravitational attraction not increase with distance, as would be the case if you were stretching a spring? the higher you lift the rock the more potential energy you impart to it. What, then, about a spacecraft that travelled from Earth to the moon, why would it be attracted by the moon’s gravity? Not only would it not have been lifted from the surface of the moon, but it should have enough potential energy to whisk it straight back to Earth as soon as it stops moving away.
Returning to the rock, if, having picked it up you altered your position so that you were holding your rock over an open well; when you released it you would be very surprised if it did not fall to the bottom of the well, in spite of the fact that you transferred to it only enough energy to take it as far as the ground surface.
There are more thoughts about, but I need to get them into some sort of order before posting them.
