Earth & SkyGreek → English
Synodic
/sɪˈnɒdɪk/adjective
Measured from one alignment of two bodies as seen from earth to the next.
The Greek roots
σύν
sýn
together, with
ὁδός
hodós
way, road
Literally: “of the coming together”
The story of the word
σύνοδος is a coming together, which is why a church council is a synod. Astronomy uses the same meeting for bodies in the sky: the synodic month of 29.5 days runs from one new moon to the next, when sun and moon line up again. That is about two days longer than the sidereal month, because the earth has moved along its own orbit in the meantime and the moon must catch up.
- How it travelled
- Ancient Greek → Latin → English
- First recorded
- 17th century
The same roots elsewhere
Other languages reached for exactly the same Greek pieces.
Same family
synodexodusmethodperiodepisode
In a sentence
Calendars built on the synodic month drift against the solar year, which is why Easter moves.
The synodic period of Mars is a little over two years, so launch windows are rare.