I understand that there is a transfer of energy between a moon and a planet depending on whether the moon is orbiting faster or slower than the spin rate of the planet. This would obviously change the orbital velocity of the moon. I also know from orbital mechanics that if you change the velocity (delta v) of an object with a circular orbit that it makes the orbit more elliptical. I'm sure that there is more at play here due to tidal influence, but I am hoping that someone here can simply explain this to me.