The classic explanation I remember from school days regarding potential energy went along the lines "If you carry a rock from the bottom of a hill to the top, that rock gains potential energy". (Although I recall no mention made of how can you measure this energy, or whether it was the energy of the matter that the rock is composed of, or something else) As an example.. If I have two equal sized lumps of matter & anti-matter & let them anhialate, I will release an amount of energy. If I take those same two lumps up to the top of a mountain and let them anhialate, will I see a larger release of energy? There will be no matter left, so was the potential energy "released"? Thanks for any clear explanation that can be offered!