Is Tidal Energy a "creation" of energy? I would like to discuss very basic idea about conversion of energy. Every form of energy we utilize (solar energy, wind energy, geothermal, fossil, hydro, etc) can be traced back to the exhaustion of some kind of energy and mass. Say solar energy, it is only possible due to fusion of H2 molecules into He molecules. Around 600 m metric tonnes/sec of H2 fuse and then the light and heat energy is expelled. Reverse engineering the fossil fuels- are only possible due to anaerobic decomposition of dead organisms; these dead organism are utilized and if they are back-tracked then we find that chemical energy they had posed were derived from plants, animals, which they had received from sun. And talking about hydro-power, the potential energy of the stream is increased due to evaporation of the water(due to wind and thermal energy derived from sun heat) from various sources. So Sun is the ultimate source of energy where some mass is at expense every time the energy is transformed. But I wonder where does energy transformation takes place in Tidal Energy. The sheer position of the Earth and the Moon and due to fluidly water. The gravitational force of moon plays a vital role but no energy is expended to "create" the energy. The moon gravitational force is strong enough to lift the tide upto certain meters and then the the tide falls back. Work is done to lift the portion of water but at what expense? No mass of moon is exhaust or any other form of energy at moon is reduced. How is it possible to create a energy out of nothing but a mere position of heavenly bodies and fluid? If not then what or which form of energy is being converted from?