My current thinking (I’m a total dilettante….) is that energy is a state in closed system. The system of course designed by the observer. For example, a cart ha

My current thinking (I’m a total dilettante….) is that energy is a state in closed system. The system of course designed by the observer. For example, a cart half way up a hill. Does it have positive or negative potential energy? Depends on how you define your system.