The Moon · History · Physics
Evection
Say it: ih-VEK-shun IPA: /ɪˈvɛkʃən/ noun
Evection: A periodic variation in the Moon's orbital motion caused by the Sun's gravitational influence.
The Moon does not follow one unchanging ellipse around Earth. Evection is one of the named corrections needed to describe its changing motion more accurately.
- Example
- The lunar theory included evection when predicting the Moon's position.
- Why astronomers use it
- It illustrates why precise lunar predictions require more than a simple two-body orbit.
- Tiny cosmic connection
- Evection changes orbital motion; libration describes the changing view of the Moon's face.
Deep Space The Moon History Physics
Where to check it
Written for Cool Moon Facts in its own words; the sources cover the same idea in more depth.