Did you know that the Moon's rotation is locked to its orbit around Earth by a bulge of material under the Moon's surface? This material is denser than the rest of the Moon's surface material, and Earth's gravity pulls on it especially strongly. The side of the Moon containing the bulge always faces Earth. We call it the
near side and we call the other side, which we never see from Earth, the
far side. People often mistakenly use the term "dark side" when referring to the far side of the Moon, forgetting that the far side is fully illuminated by the Sun whenever we see a new moon from Earth.
If we were to look from high above the Earth-Moon system, we would see the Moon rotate once per month with respect to the stars. This is its sidereal ro ...