Where does the energy responsible for tidal forces come from?

Question

So, I’m aware that tides are caused by the Moon’s gravity acting on the surface of the earth. That said, tidal forces move an obscene amount of matter from point A to point B and back to point A again. Where does that energy come from that doesn’t break the first law of thermodynamics? Followup question: If we harvest energy from the system using turbines or something similar, what effect does that have on the system?

In: Physics

Answer 1

The ultimate energy source is the kinetic energy of the Earth’s spin. Harvesting tidal energy will in fact cause the Earth to turn slower. But not enough to worry about.