It is rarely that I can contribute to this group, but this is one of those times. Orbital precession does not result from the application of a force *per se* to a satellite; it is rather the result of a net torque acting on the revolving satellite over an entire orbit. Since these effects can be seen in the simplest of models*, circular orbits about an oblate ellipsoidally symmetric Earth, we will discuss that sort of orbit. The argument below depends strongly on appreciating the symmetry of the problem. First we must define the angular momentum of the orbit. It is a vector quantity which can be considered as oriented perpendicularly to the plane of the orbit and originating at the focus of the orbit, the center of Earth. (Vector quantities are really not anchored to any point in space, but it aids visualization to consider them in that way.) Applied torque can change the direction of an angular momentum vector if there is a component of that torque in a direction perpendicular to the angular momentum vector. (There is a simple analog of Newton's second law of motion which is the vector differential equation to which Bruno is referring.) If the gravitational force acting on the satellite always lies in the plane of the satellite's orbit then when the net torque acting on the satellite with respect to the center of its orbit is added up around a complete orbit it will be found that there is no net torque acting on the satellite. This condition holds only for two special cases of our simple model, however: the equatorial and the polar orbits. For all other orbits there is an out of plane force acting whenever the satellite is located away from the Earth's equatorial plane. This out- of-plane force is a tidal force due to the relative proximity of the nearer bulge material. The torque due to this out-of-plane force adds up constructively around each inclined orbit to yield a net torque which is perpendicular to the angular momentum of the satellite orbit. The consequence is a precession of the orbital plane. Lacking graphical capability and the feedback from talking directly to the student I can't really do better than that. I suspect that I have said enough in words so that the original questioner will understand my answer, but I'd be glad to answer questions. Leigh *Yes, there is a very small general relativistic effect associated with the rotation of the Earth. I believe it has never been detected and I will certainly ignore it here.