> because it is lowering it's potential energy. There’s also kinetic energy. The Earth rotates, and we have the Moon. It’s theoretically possible to build a ma

> because it is lowering it's potential energy. There’s also kinetic energy. The Earth rotates, and we have the Moon. It’s theoretically possible to build a machine which harvests energy from that rotation. Tides are powered by that energy, it’s obvious one could build a machine to extract energy from tidal waves in the ocean. It should be possible to build a machine which extracts that energy directly, without the water. Probably not practical because the energy density is too low, and the machine needs to be prohibitively massive.