Let's say I lift a 50 pound weight with my arms to shoulder height (say, 4 feet). The "work" that I did to get the weight up there (the energy I put in) has now been converted to "potential energy" because it is perched in a position where it can then convert that into kinetic energy. But, that potential energy is there only because of the Earth's gravity, right? If I were to let go of the weight, it would convert the energy I put in to lift it (potential energy) into kinetic energy -- falling towards Earth. In other words, that potential energy exists only because of Earth's gravity. .... Suppose I were to lift the weight 4 feet in the air, and then Earth disappeared or vanished or lost a lot of mass or whatever. Just say the earth went away. Wouldn't the weight then lose its potential energy (because the earth is no longer there)? EDIT: How would this situation satisfy the Conservation of Energy rule?