ASTR 101 Lecture 7: Precession
Document Summary
For an object to precede it have to have. Closer to spherical, it will have a slower precession. Earth is only very mildly non-spherical, so it precedes very slowly compared to its rotation: earth"s rotation axis precesses 360 every 26,000 tropical years. The rotation axis of the top cannot be parallel or perpendicular to the force. Because of precession, earth"s rotation axis points toward the sun 20 minutes earlier in its orbit each year and the north celestial pole moves by 20 arcseconds each year. Season begin 20 minutes earlier than they would if there was no precession. Polaris is not always close to the north celestial pole.
