where

Equation (11.337) implies that the perigee precesses (i.e., its longitude increases in time) at the mean rate of degrees per year. (Of course, a year corresponds to .) Furthermore, it is clear that this precession is entirely due to the perturbing influence of the Sun, because it depends only on the parameter , which is a measure of this influence. Given that , we find that the perigee advances by degrees per year. Hence, we predict that the perigee completes a full circuit about the Earth every years. In fact, the lunar perigee completes a full circuit every years. Our prediction is somewhat inaccurate because our previous analysis neglected , and smaller, contributions to the parameter [see Equation (11.284)], and these turn out to be significant. (See Section 11.17.)