Nutation

The nutation is a periodic swinging of the axis of rotation of the Ground around its average position in addition to the Précession, discovered in 1748 by the British astronomer James Bradley. Had with the combined attraction of the Sun and the the Moon, nutation results in an oscillation of the axis of rotation of the Earth which can go until 17,2" (seconds of arc) in 18,6 years, this is why the celestial catalogs of coordinates are given regularly up to date in the history.

See too

• Precession

• Precession of the equinoxes

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