Very basic question, I am almost embarrased to ask it... If I had to hold say a clock or a wall unit above the ground it would take energy for me to do so. I would need to eat food to get energy to support the clock in my arms, and if I ran out of energy I would drop it. If I put a nail in the wall and hung the clock on it, the wall supports it. For years on end. But where does the energy come from to support the clock?