There is a permanently dark side of the Moon
The Moon has a far side that always faces away from Earth due to tidal locking, but this far side receives just as much sunlight on average as the near side. The word 'dark' in the popular phrase historically meant 'unknown', not 'unilluminated'.
What we know
Because the Moon's rotation period and orbital period around Earth are equal, a phenomenon called tidal locking, the same face of the Moon always points toward Earth. The far side remained unseen from Earth until 1959, when the Soviet spacecraft Luna 3 returned the first photographs. This is why it was described as the 'dark side', using dark to mean hidden or unknown.
However, the far side of the Moon is not perpetually dark in the sense of receiving no sunlight. As the Moon orbits the Sun (along with Earth), every part of its surface cycles through periods of illumination and darkness. During a new moon as seen from Earth, it is actually the near side facing away from the Sun that is dark, while the far side is fully illuminated. Each location on the Moon receives roughly two weeks of sunlight followed by two weeks of night per lunar month.
NASA confirmed this when its Deep Space Climate Observatory photographed the fully illuminated far side of the Moon in 2015. Lunar missions including the Lunar Reconnaissance Orbiter have mapped the far side in detail, showing it to be brighter overall than the near side because it has fewer dark volcanic maria and a higher proportion of reflective highlands.
The popular misconception is reinforced by the famous Pink Floyd album title, which uses the term in its poetic rather than literal sense.
Common claims
- The far side of the Moon never gets sunlightFalse - gets equal sunlight on average
- The dark side is permanently frozenFalse - temperature cycles like the near side
- Tidal locking keeps one face always darkFalse - locking affects Earth-facing orientation, not sunlight