<Tr> <Td> precession of nodes </Td> <Td> 18.5996 years </Td> </Tr> <Tr> <Td> precession of line of apsides </Td> <Td> 8.8504 years </Td> </Tr> <P> The Moon orbits Earth in the prograde direction and completes one revolution relative to the stars in about 27.322 days (a sidereal month) and one revolution relative to the Sun in about 29.530 days (a synodic month). Earth and the Moon orbit about their barycentre (common center of mass), which lies about 4,600 km (2,900 mi) from Earth's center (about 3 / 4 of the radius of Earth). On average, the distance to the Moon is about 385,000 km (239,000 mi) from Earth's center, which corresponds to about 60 Earth radii . With a mean orbital velocity of 1.022 km / s (2,290 mph), the Moon covers a distance approximately its diameter, or about half a degree on the celestial sphere, each hour . The Moon differs from most satellites of other planets in that its orbit is close to the ecliptic plane instead of that of its primary (in this case, the Earth's equatorial plane). The Moon's orbital plane is inclined by about 5.1 ° to the ecliptic plane, whereas the Moon's equatorial plane is tilted by only 1.5 ° . </P> <P> The properties of the orbit described in this section are approximations . The Moon's orbit around Earth has many irregularities (perturbations), the study of which (lunar theory) has a long history . </P>

What is the movement of the moon around the earth called