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“nutation”
A slight "nodding" of the Earth in space: A nutation is caused by the varying gravitational pulls of the Sun and Moon.
Nutation changes the angle of the Earth's axial tilt (average of about 23.5°) by about nine seconds of arc to either side of its mean position. A complete cycle takes just over 18.5 years.
This entry is located in the following unit:
Astronomy and related astronomical terms
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