Britannica Sources used in this answer

Why does the Moon always show nearly the same side to Earth?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

near and far sides of Earth's Moon — Moon (Left) Near side of Earth's Moon, photographed by the Galileo spacecraft on its way to Jupiter. (Right) Far side of the Moon with some of the near side visible (upper right), photographed by the Apollo 16 spacecraft.

The Moon always shows nearly the same side to Earth because of tidal interactions between the two bodies.1

Over time, the gravitational attraction between Earth and the Moon caused cyclic deformations in the Moon's shape, known as tidal bulges. These interactions exerted a torque on the Moon that gradually braked its rotation. This process continued until the Moon’s spin rate became synchronous with its orbital period—meaning it now rotates at the same rate that it revolves around Earth.12

While the Moon keeps the same face toward our planet, observers on Earth can actually see slightly more than 59 percent of the lunar surface over time. This occurs due to libration, an apparent oscillation caused by the combination of the Moon's constant spin rate and its varying orbital speed, as well as the Moon's slight rocking motions in longitude and latitude.1