This has troubled me ever since we went over gravity in science. I didnt ask the teacher becuase i thought the answer might be obvious and I might look like an idiot in front of the class lol. But anyway, I was wondering where the energy comes from that an object has when it is in a gravitational field. Where does the energy come from that my bookbag has when I lift it from the floor. I thought its the same amount of energy I transferred to the bookbag when I lifted it, but what then about the case of a meteor or some other extra-terrestrial object?