imagine a sun and a planet, both rigid and perfectly spherical. the distance between the center of mass of these two bodies is much greater than the radius of both bodies. considering newton's inverse square law of gravity: now, due to the non-uniform nature of this gravity, different parts of the planet experiences different forces. let's say the planet is spinning around a axis with a non-zero inclination angle. the tidal forces would actually result in a torque even though the planet is perfectly spherical and it would result in precession. i have worked out some basic intrgrations and approximation regarding this problem. perhaps someone can tell me if it has been discovered before and information about it? i know tidal force... but what about "tidal torque"?