I have been pondering on this for a while. Gravity is a force, not energy. But where is the energy that produce gravity? For an example. If there only Earth and Moon existed and nothing else exists. (People and water are located underground inside the Earth or whatever the case that may be.) If the moon kept in perfect orbit where it does not move away or closer and creates the tides for water underground. People could produce energy from the tide, so where all the energy coming from? If gravity is not a form of energy, then what is the energy that produce gravity? Does this break the "Law of Nature" philosophy in term of energy being not created? Please and thank you for your time.