Editing Axial precession (section)

==Nomenclature==
[[File:Gyroscope precession.gif|thumb|300px|[[Precession]] of a [[gyroscope]].  In a similar way to how the force from the table generates this phenomenon of precession in the spinning gyro, the gravitational pull of the Sun and Moon on the Earth's equatorial bulge generates a very slow precession of the Earth's axis (see [[#Cause|§Cause]]).  This off-center push or pull causes a torque, and a torque on a spinning body results in precession.  The gyro can be analyzed in its parts, and each part within the disk is trying to fall, but the rotation brings it from down to up, and the net result of all particles going through this is precession.]]
The term "[[Precession]]" is derived from the Latin ''[[wikt:praecedo|praecedere]]'' ("to precede, to come before or earlier"). The stars viewed from Earth are seen to proceed from east to west daily (at about 15 degrees per hour), because of the Earth's [[diurnal motion]], and yearly (at about 1 degree per day), because of the Earth's revolution around the Sun. At the same time the stars can be observed to anticipate slightly such motion, at the rate of approximately 50 arc seconds per year (1 degree per 72 years), a phenomenon known as the "precession of the equinoxes".

In describing this motion astronomers generally have shortened the term to simply "precession". In describing the ''cause'' of the motion physicists have also used the term "precession", which has led to some confusion between the observable phenomenon and its cause, which matters because in astronomy, some precessions are real and others are apparent. This issue is further obfuscated by the fact that many astronomers are physicists or astrophysicists.

The term "precession" used in [[astronomy]] generally describes the observable precession of the equinox (the stars moving [[Apparent retrograde motion|retrograde]] across the sky), whereas the term "precession" as used in [[physics]], generally describes a mechanical process.