The Moon’s motion around Earth is more complex than a simple circular orbit. Its orbital plane is inclined by about 5° to the Earth’s orbital plane (the ecliptic), so the Moon continually moves above and below the ecliptic plane.

Beyond this rapid monthly journey, however, lies a much slower and more intricate celestial dynamic.

Due to the Sun’s gravitational pull on the Moon’s tilted orbit, the orientation of the Moon’s entire orbital plane slowly changes. This movement is called precession, and one complete cycle takes about 18.6 years. Thus, while the Moon circles Earth roughly every 27.3 days, the plane in which it travels slowly shifts in the opposite (retrograde) direction.

Two planes intersect in a line. Since the Moon’s orbital plane intersects the ecliptic, this slowly changing orientation causes their line of intersection to slowly rotate as well.

So there are really two very different motions:

Moon races around Earth; its orbital plane slowly turns. And it is this slow, almost sideways or wobbling movement of the orbital plane—rather than the 5° inclination alone—that produces the slowly moving intersection directions.