Axial precession
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Axial precession is the slow change in the orientation of a rotating body's axis. Earth's axis traces a broad circle in the sky, similar to the wobble of a spinning top, while maintaining roughly the same tilt relative to the plane of its orbit.
The motion is caused mainly by gravitational torques from the Moon and Sun acting on Earth's equatorial bulge. Planetary influences also contribute smaller effects.
Earth's full precessional cycle takes about 25,700 years. As the axis changes direction, the celestial poles move among the stars and the positions of the equinoxes shift westward along the ecliptic.
Precession affects astronomical coordinate systems, calendars, long-term star positions, and the seasonal distribution of sunlight. Together with changes in orbital eccentricity and axial tilt, it forms part of the Milankovitch cycles associated with long-term climate change.
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- Source / publisher: Wikipedia
- URL type: WWW
- Credits: Wikipedia
- URL: https://en.wikipedia.org/wiki/Axial_precession