The Moon Gave Us the Month
The moon is Earth's natural satellite. Its cycle named a unit of time still in use.
The moon is Earth's natural satellite, and by extension any planet's. *Moon* and *month* are the same word: both come from a root meaning to measure, because the moon's cycle was the first calendar. The lunar month runs about 29.5 days, which is why twelve of them fall eleven days short of a solar year and why purely lunar calendars drift through the seasons. The moon also keeps one face turned to Earth, locked by tidal forces over billions of years.
- Earth's satellite. *A full moon.*
- Any satellite. *The moons of Jupiter.*
- A lunar month. *Many moons ago.*
- Month — the same root. *A month.*
- Old English — *mona*. *The source.*
Word forms
| Form | Word | Example |
|---|---|---|
| Noun | moon | The moon. |
| Plural | moons | Moons. |
| Adjective | lunar | Lunar. |
| Related | month | A month. |
| Old English | mona | The moon. |
- The full moon rose.Astronomy.
- Moon and month share a root.Etymology.
- It always shows one face.Fact.
Why we see only one side
- Tidal forces slowed the moon's rotation over time
- It now turns once per orbit, called tidal locking
- The same face is always toward Earth
- Libration lets us glimpse about 59 percent in total
- The far side was first photographed in 1959
Old English *mona*, from a Germanic root shared with *month*, ultimately from a root meaning to measure.
Are moon and month related?
Yes. Both descend from a root meaning to measure, since the moon's cycle was the earliest calendar.
Why does the moon show one face?
Tidal forces slowed its rotation until it turned once per orbit, an effect called tidal locking.