The phrase “dark side of the Moon” is a common term that brings up questions about Earth’s closest celestial neighbor. The simple answer to whether you can see it hinges on what “dark side” truly means. The Moon’s movements relative to the Earth and the Sun dictate which portions are visible and which are illuminated, leading to a difference between the face we see and the one that is always turned away. The misconception suggests a perpetually shadowed hemisphere, but the truth involves a fascinating interplay of gravity and orbital mechanics.
Defining the Near Side and the Far Side
The correct scientific terms for the Moon’s two hemispheres are the Near Side and the Far Side. The Near Side constantly faces Earth due to synchronous rotation, making it the only hemisphere ever visible from our planet’s surface. A slight wobble in the Moon’s orbit, known as libration, allows observers on Earth to occasionally glimpse about 9% more of the Far Side, meaning a total of about 59% of the surface is viewable over the course of an orbit.
The Far Side is the hemisphere always oriented away from Earth, and it was entirely unseen by human eyes until the Soviet probe Luna 3 photographed it in 1959. The term “dark side” is often incorrectly used as a synonym for the Far Side, which causes confusion. In this context, “dark” should be interpreted as “unseen” or “unknown” rather than literally unilluminated by the Sun.
The Mechanism of Synchronous Rotation
We consistently see only the Near Side due to synchronous rotation, a stable orbital arrangement resulting from billions of years of gravitational interaction between the Earth and the Moon. This state, also known as tidal locking, means the Moon’s period of rotation on its axis is exactly the same length as its orbital period around the Earth, both lasting approximately 27.3 Earth days. As the Moon travels along its orbit, it must simultaneously rotate once to keep the same face directed toward us.
This process began when the Moon was younger and rotated much faster. Earth’s immense tidal forces created a slight, permanent bulge on the Moon, allowing gravity to slow the rotation over time. This gravitational tug continued until the bulge was aligned with the Earth, locking its spin and orbital periods together in a stable gravitational equilibrium.
Illumination and the Changing “Dark Side”
The true “dark side” of the Moon is the hemisphere currently experiencing night, a portion that constantly shifts due to the Sun’s light. Just like Earth, the Moon rotates, so every part of its surface experiences approximately two weeks of daylight followed by two weeks of darkness during its 29.5-day cycle. The Moon’s phases, which we observe from Earth, result from how much of the sunlit Near Side is visible to us.
During the New Moon phase, the Moon is positioned between the Earth and the Sun, meaning the Near Side is fully shadowed and appears “dark.” At this time, the Far Side is completely illuminated by the Sun, experiencing its full lunar day, proving it is not permanently dark.
Physical Characteristics of the Far Side
Images and data from robotic missions show that the Far Side is dramatically different from the familiar Near Side. Its terrain is rugged and heavily cratered, with a distinct lack of the large, dark plains known as maria. While maria cover over 30% of the Near Side, they make up only about 1% of the Far Side’s surface area.
Scientists believe this difference is due to the Moon’s crust being significantly thicker on the Far Side. The thinner crust on the Near Side allowed ancient impacts to penetrate deeper and release subsurface magma, which solidified to form the dark basaltic maria. Conversely, the Far Side’s thicker crust resisted this magma flow, resulting in a surface dominated by brighter, heavily pockmarked highlands.
China’s Chang’e 4 mission made history in 2019 by achieving the first soft landing on this hemisphere, confirming its rugged geology.