Is there really a dark side of the Moon?

There is no permanent dark side of the Moon. The far side receives as much sunlight as the near side, and the Moon has a day side and a night side that change as it rotates, much as Earth's do. Astronomers prefer the terms near side and far side to avoid confusion. [1] [2]

The Moon takes as long to rotate once on its axis as it does to orbit Earth once, so the same side always faces us. This is called synchronous rotation, and it results from tidal locking, which involves gravity and the same kinds of forces that cause ocean tides. According to [science.nasa.gov](https://science.nasa.gov/moon/top-moon-questions/), if the Moon did not rotate, or rotated at another rate, we would see different parts of it through the month. The Moon does rotate, even though it may not look like it from here. [1] [3] [2]

The sources give slightly different figures for the period involved: one NASA page says 29 days, and BBC Sky at Night Magazine says 28 days. These are rounded values for the same cycle. [4] [2]

The Sun always lights half the Moon. When the near side is fully lit, we see a full Moon. When the far side is fully lit and the near side is dark, we see a new Moon. Other phases show the boundary between lunar day and lunar night. During a crescent Moon, for example, most of the far side is in daylight. Moon phases are not caused by Earth's shadow, which matters only during a lunar eclipse. [1]

Over a year, the far side actually gets slightly more sunlight than the near side. The near side loses some time to Earth's shadow during lunar eclipses, although it also receives sunlight reflected from Earth. BBC Sky at Night Magazine reports that a full Earth seen from the Moon is 34 times brighter than a full Moon seen from Earth. [2]

"Dark" can mean unknown or unexplored, and for a long time the far side was hidden from view. Libration, a slight apparent wobble caused by variations in the Earth-Moon distance, lets observers on Earth glimpse regions near the edge, including Mare Orientale and Crater Einstein. These make up around 18 percent of the far side, leaving about 82 percent permanently out of sight. Orbiting spacecraft in the late 1950s and early 1960s began imaging it, and the whole far side has since been photographed and mapped. China's Chang'e 4 landed there in 2019 and Chang'e 6 in 2024. [2]

NASA's Scientific Visualization Studio says the far side is "dark" only in the archaic sense of mysterious or unknown. There is also a modern sense: the Moon blocks radio signals to and from craft orbiting behind it, so they "go dark" in communications. [5] [2]