Why we only ever see one side of our Moon
In short: The Moon appears to be locked in a permanent face-to-face relationship with Earth, but this is the result of a specific physical motion. This video explains why we never see the lunar far side and how its rotation works.
The Moon undergoes synchronous rotation, meaning the time it takes to rotate once on its own axis is exactly equal to the time it takes to orbit Earth. Our planet constantly views one lunar hemisphere due to these motions being perfectly synchronised. Various areas of its exterior would become visible during a month if its rotation speed differed.
While a full revolution around Earth takes 27.3 days, it takes about 29.5 days to cycle from one new moon to the next. This discrepancy occurs because both the Earth and Moon are moving around the Sun simultaneously, changing the angle at which sunlight hits the lunar surface.
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Sources
- Summary by Intellect · source: Why Do We Have One Moon? | Astronomic
- Also: Top Moon Questions Does the Moon rotate? Are Moon phases the same everywhere on Earth? Is there a "dark side of the Moon"? Your top questions, answered.
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