<P> The Moon's elongation is its angular distance east of the Sun at any time . At new moon, it is zero and the Moon is said to be in conjunction . At full moon, the elongation is 180 ° and it is said to be in opposition . In both cases, the Moon is in syzygy, that is, the Sun, Moon and Earth are nearly aligned . When elongation is either 90 ° or 270 °, the Moon is said to be in quadrature . </P> <P> The orientation of the orbit is not fixed in space, but rotates over time . This orbital precession is also called apsidal precession and is the rotation of the Moon's orbit within the orbital plane, i.e. the axes of the ellipse change direction . The Moon's major axis--the longest diameter of the orbit, joining its nearest and farthest points, the perigee and apogee, respectively--makes one complete revolution every 8.85 Earth years, or 3,232.6054 days, as it rotates slowly in the same direction as the Moon itself (direct motion). The Moon's apsidal precession is distinct from, and should not be confused with its axial precession . </P> <P> For the moon to make a complete rotation on its axis it takes approximately 27.3 days . It takes the moon about this same time to orbit the earth . </P> <P> The mean inclination of the lunar orbit to the ecliptic plane is 5.145 ° . The rotational axis of the Moon is also not perpendicular to its orbital plane, so the lunar equator is not in the plane of its orbit, but is inclined to it by a constant value of 6.688 ° (this is the obliquity). This does not mean that, as a result of the precession of the Moon's orbital plane, the angle between the lunar equator and the ecliptic would vary between the sum (11.833 °) and difference (1.543 °) of these two angles, but, as was discovered by Jacques Cassini in 1722, the rotational axis of the Moon precesses with the same rate as its orbital plane, but is 180 ° out of phase (see Cassini's Laws). Therefore, the angle between the ecliptic and the lunar equator is always 1.543 °, even though the rotational axis of the Moon is not fixed with respect to the stars . </P>

How long does it take for the moon to rotate around the earth