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Webster 1913 Edition
Precession
Pre-ces′sion
,Noun.
The act of going before, or forward.
Lunisolar precession
. (Astron.)
See under
– Lunisolar
. Planetary precession
, that part of the precession of the equinoxes which depends on the action of the planets alone.
– Precession of the equinoxes
(Astron.)
, the slow backward motion of the equinoctial points along the ecliptic, at the rate of 50.2˝ annually, caused by the action of the sun, moon, and planets, upon the protuberant matter about the earth’s equator, in connection with its diurnal rotation; – so called because either equinox, owing to its westerly motion, comes to the meridian sooner each day than the point it would have occupied without the motion of precession, and thus precedes that point continually with reference to the time of transit and motion.
Webster 1828 Edition
Precession
PRECES'SION
,Noun.
1.
Literally, the act of going before, but in this sense rarely or never used.2.
In astronomy, the precession of the equinox, is an annual motion of the equinox, or point when the ecliptic intersects the equator, to the westward, amounting to 50 l/2'. This precession was discovered by Hipparchus, a century and a half before the christian era,though it is alleged that the astronomers of India had discovered it long before. At that time, the point of the autumnal equinox was about six degrees to the eastward of the star called spica virginis. In 1750, that is, about nineteen hundred years after, this point was observed to be about 20 deg. 21' westward of that star. Hence it appears that the equinoctial points will make an entire revolution in about 25,745 years.Definition 2024
precession
precession
See also: précession
English
Alternative forms
- præcession (obsolete)
Noun
precession (countable and uncountable, plural precessions)
- (uncountable) precedence
- But as it will not do to talk entirely at random, as Montaigne does, and Ralph Waldo Emerson tries to do, we must take up some little thread or threads. and string our thoughts thereupon, keeping up also a relation among them of precession and succession.
- (physics, countable) The wobbling motion of the axis of a spinning body when there is an external force acting on the axis.
- (astronomy, uncountable) The slow gyration of the earth’s axis around the pole of the ecliptic, caused mainly by the gravitational torque of the sun and moon.
- Any of several slow changes in an astronomical body's rotational or orbital parameters.
Derived terms
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Translations
physics term
astronomical term
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