The phenomenon of seeing only one side of the Moon is known as tidal locking or synchronous rotation. It occurs when the rotational period of an astronomical body matches its orbital period around another object. In the case of the Moon, it is tidally locked to the Earth, resulting in the same face always facing Earth. Several factors contribute to this unique phenomenon.

Gravitational Forces: The gravitational forces between the Earth and the Moon play a significant role in causing tidal locking. The gravitational attraction of the Earth causes a tidal bulge on the Moon, distorting its shape slightly. Over time, these tidal forces have acted as a braking mechanism, gradually slowing down the Moon's rotation. As a result, the Moon's rotational period has synchronized with its orbital period around the Earth.

Centrifugal Force: The Moon's rotation creates a centrifugal force that tries to push it away from the Earth. However, the gravitational force of the Earth counteracts this outward force, creating a gravitational gradient across the Moon. This gradient causes a torque that slows down the Moon's rotation until it becomes tidally locked.

Orbital Resonance: The Moon's orbit around the Earth is not a perfect circle but rather an ellipse. This elliptical orbit, combined with the gravitational forces from the Sun and the Earth, creates an effect known as orbital resonance. The gravitational interactions of these bodies cause the Moon's orbit to be slightly eccentric, resulting in variations in the distance between the Earth and the Moon. Over time, these variations reinforce the tidal forces and contribute to tidal locking.

Conservation of Angular Momentum: The process of tidal locking is a manifestation of the principle of conservation of angular momentum. As the Moon's rotation slows down, its angular momentum decreases. This decrease is compensated by an increase in the angular momentum of the Earth-Moon system as a whole.

The result of these factors is that the Moon's rotation has become synchronized with its orbit around the Earth, leading to one side of the Moon always facing us. The side that faces away from Earth is called the "far side" or "dark side" of the Moon, although it receives sunlight just like the near side.

It's important to note that while we see only one side of the Moon from Earth, space missions have provided us with views of the far side. The Soviet Luna 3 mission in 1959 captured the first images of the Moon's far side, and subsequent missions like NASA's Lunar Reconnaissance Orbiter have provided detailed mapping and imaging of the entire lunar surface.

The phenomenon of tidal locking is not unique to the Moon-Earth system and can be observed in other celestial bodies that orbit closely around larger objects. Understanding tidal locking has broader implications in the study of planetary formation, the dynamics of celestial bodies, and the long-term evolution of astronomical systems.