The Moon does rotate
It is common to hear that the Moon keeps one side facing Earth because it does not rotate. The opposite is true. The Moon rotates once on its axis in the same time it takes to complete one orbit around Earth: about 27.3 days relative to the stars.
Imagine walking around a table while always facing its center. By the time you complete the circuit, you have also turned once relative to the room. The Moon does the same thing.
Gravity created a stable lock
Early in lunar history, the Moon probably rotated faster. Earth’s gravity raised tides in the Moon’s body. Friction associated with those deformations dissipated rotational energy until the rotation settled into a stable one-to-one relationship with the orbit. This state is called tidal locking or synchronous rotation.
Many moons in the solar system are similarly locked to their planets.
The view still changes slightly
The orbit is elliptical and tilted, so the Moon appears to rock east-west and north-south. These librations reveal slivers beyond the average edge. Across a full cycle, observers can see about 59 percent of the lunar surface.
The far side is therefore not the same as a permanently hidden half, and it is not permanently dark. Spacecraft are required to see its central regions directly.
