Man in the Moon then cooled, becoming smooth, basalt rock. The near side of the Moon, containing these maria that make up the man, is always facing Earth. This is due to a tidal locking or synchronous orbit. Thought to have occurred because of the gravitational forces partially caused by the Moon's oblong shape, its rotation has slowed to the point where it rotates exactly once on each trip around the Earth. This causes the near side of the Moon to always turn its face toward Earth. Man in the Moon The Man in the Moon refers to any of several pareidolic images of
Orbit of the Moon forward). The bulge on the side furthest from the Moon has the opposite effect, but because the gravitational attraction varies inversely with the square of distance, the effect is stronger for the near-side bulge. As a result, some of Earth's angular (or rotational) momentum is gradually being transferred to the rotation of the Earth–Moon pair around their mutual centre of mass, called the barycentre. This slightly faster rotation causes the Earth–Moon distance to increase at approximately 38 millimetres per year. Conservation of angular momentum means that Earth's axial rotation is gradually slowing, and because of this its day lengthens by