Solved cryptogram
The moon keeps one face toward us because its spin and its orbit take exactly the same time.
Astronomy Facts, sourced to NASA.
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What it means
This is called tidal locking, and it is not a coincidence. Earth's gravity raises a slight bulge in the moon's solid body, and over billions of years the tug on that bulge braked the moon's rotation until it matched its orbital period. The same thing has happened to many moons in the solar system. A wobble in the moon's orbit lets us peek at a little over half its surface in total.
The claim comes from NASA.
- SourceNASA
- CollectionAstronomy Facts
- Difficultymedium
- Length74 letters, 21 unique
Nearby in the collection
The facts either side of this one.
About as hard as this one
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