Synchronous Rotation

The moon is the only natural satellite of the earth, and it is the fifth-largest moon in the solar system. It is the largest natural satellite in the solar system relative to the size of the planet it orbits.

The moon is tidally locked, or in captured rotation, with Earth. That means that the moon always shows us the same face. The effect is known as synchronous rotation.

Synchronous rotation means that the moon rotates about its axis in the same amount of time it takes to orbit the earth. This results in the moon always keeping the same face turned towards the earth, as seen in the animation above on the left. If the moon were not spinning at all, it would alternately show its near and far sides to the earth while moving around our planet in orbit, as shown in the animation above on the right.

Below are photos of the moon from both sides. Because of the synchronous rotation, we never see the far side of the moon.