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precession
precession The wobbling motion of a spinning top or gyroscope in which the axis of rotation gradually sweeps out a conical shape. The spinning Earth undergoes a slow precession, due to the combined gravitational attractions of the Sun, Moon, and planets. The Earth's pole takes about 25 800 years to describe one complete circle on the celestial sphere; this circle has a radius of approximately 23 °.5, i.e. the inclination of the Earth's axis. The equinoxes make one circuit of the ecliptic in the same time. As a result of precession, the right ascension and declination of stars change with time, so the date or epoch for which these coordinates apply must always be stated. See also lunisolar precession; planetary precession; precession of the equinoxes.
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"precession." A Dictionary of Astronomy. 1997. Encyclopedia.com. 27 May. 2012 <http://www.encyclopedia.com>. "precession." A Dictionary of Astronomy. 1997. Encyclopedia.com. (May 27, 2012). http://www.encyclopedia.com/doc/1O80-precession.html "precession." A Dictionary of Astronomy. 1997. Retrieved May 27, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O80-precession.html |
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precession
precession The action of a couple whose axis is perpendicular to the rotational axis (a torque) on a rotating body causing its axis of rotation to trace out a path about an average position, instead of having a constant alignment, i.e. the axis of rotation itself revolves conically about a central point. The Earth's axis of rotation precesses as a result of several forces, e.g. changes in mass distribution on its surface, changes in the gravitational field due to changes in the relative positions of the Moon, Sun, and planets, etc.
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AILSA ALLABY and MICHAEL ALLABY. "precession." A Dictionary of Earth Sciences. 1999. Encyclopedia.com. 27 May. 2012 <http://www.encyclopedia.com>. AILSA ALLABY and MICHAEL ALLABY. "precession." A Dictionary of Earth Sciences. 1999. Encyclopedia.com. (May 27, 2012). http://www.encyclopedia.com/doc/1O13-precession.html AILSA ALLABY and MICHAEL ALLABY. "precession." A Dictionary of Earth Sciences. 1999. Retrieved May 27, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O13-precession.html |
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precession
precession Wobble of the axis of a spinning object. It occurs as a result of the torque on the spin axis, which increases as the angle of precession increases. The Earth precesses about a line through its centre and perpendicular to the plane of the ecliptic extremely slowly (a complete revolution taking 25,800 years) at an angle of 23.5°. The motion of a gyroscope is another consequence of precession, because the entire ring containing the spinning wheel and its axle precesses around the support pivot.
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"precession." World Encyclopedia. 2005. Encyclopedia.com. 27 May. 2012 <http://www.encyclopedia.com>. "precession." World Encyclopedia. 2005. Encyclopedia.com. (May 27, 2012). http://www.encyclopedia.com/doc/1O142-precession.html "precession." World Encyclopedia. 2005. Retrieved May 27, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O142-precession.html |
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precession
pre·ces·sion / prəˈseshən/ • n. Physics the slow movement of the axis of a spinning body around another axis due to a torque (such as gravitational influence) acting to change the direction of the first axis. It is seen in the circle slowly traced out by the pole of a spinning gyroscope. DERIVATIVES: pre·cess / prēˈses; ˈprēˌses/ v. pre·ces·sion·al / priˈseshənl/ adj. |
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"precession." The Oxford Pocket Dictionary of Current English. 2009. Encyclopedia.com. 27 May. 2012 <http://www.encyclopedia.com>. "precession." The Oxford Pocket Dictionary of Current English. 2009. Encyclopedia.com. (May 27, 2012). http://www.encyclopedia.com/doc/1O999-precession.html "precession." The Oxford Pocket Dictionary of Current English. 2009. Retrieved May 27, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O999-precession.html |
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precession
precession (astron.) of the equinoxes. XVI. — late L. præcessiō, -ōn-, f. præcēdere PRECEDE.
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T. F. HOAD. "precession." The Concise Oxford Dictionary of English Etymology. 1996. Encyclopedia.com. 27 May. 2012 <http://www.encyclopedia.com>. T. F. HOAD. "precession." The Concise Oxford Dictionary of English Etymology. 1996. Encyclopedia.com. (May 27, 2012). http://www.encyclopedia.com/doc/1O27-precession.html T. F. HOAD. "precession." The Concise Oxford Dictionary of English Etymology. 1996. Retrieved May 27, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O27-precession.html |
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precession
precession see gyroscope . |
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"precession." The Columbia Encyclopedia, 6th ed.. 2011. Encyclopedia.com. 27 May. 2012 <http://www.encyclopedia.com>. "precession." The Columbia Encyclopedia, 6th ed.. 2011. Encyclopedia.com. (May 27, 2012). http://www.encyclopedia.com/doc/1E1-X-precessi.html "precession." The Columbia Encyclopedia, 6th ed.. 2011. Retrieved May 27, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1E1-X-precessi.html |
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