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Topic: Precession

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In the News (Mon 22 Apr 19)

 Precession - Wikipedia, the free encyclopedia
Precession is the resultant of the angular velocity of rotation and the angular velocity produced by the torque.
The Earth's precession of the equinoxes is an important part of the astronomical theory of ice ages.
Discrepancies between the observed perihelion precession rate of the planet Mercury and that predicted by classical mechanics were prominent among the forms of experimental evidence leading to the acceptance of Einstein's Theory of Relativity, which predicted the anomalies accurately.
en.wikipedia.org /wiki/Precession   (1277 words)

To astronomers precession is mainly another factor to be taken into account when aiming a telescope or drawing a star chart; but to believers in astrology, the "dawning of the age of Aquarius" is a great portent and may mark the beginning of a completely new and different era.
The axis of the cone is perpendicular to the plane of the ecliptic.
The cause of the precession is the equatorial bulge of the Earth, caused by the centrifugal force of the Earth's rotation (the centrifugal force is discussed in a later section).
www-istp.gsfc.nasa.gov /stargaze/Sprecess.htm   (2050 words)

 AllRefer.com - precession of the equinoxes (Astronomy, General) - Encyclopedia
B.C. The precession is due to the gravitational attraction of the moon and sun on the equatorial bulge of the earth, which causes the earth's axis to describe a cone in somewhat the same fashion as a spinning top.
There is some further precession caused by the gravitational influences of the other planets; this precession affects the earth's orbit around the sun and thus causes a shift of the ecliptic on the celestial sphere.
The precession of the earth's orbital plane is sometimes called planetary precession, and that of the earth's equatorial plane (caused by the sun and moon) is called luni-solar precession; the combined effect of the moon, the sun, and the planets is called general precession.
reference.allrefer.com /encyclopedia/P/precequi.html   (454 words)

 Precession of the Equinoxes - Crystalinks
The Earth goes through one complete precession cycle in a period of approximately 25,800 years, during which the positions of stars as measured in the equatorial coordinate system slowly change.
The change in celestial coordinates in relation to earth's topographic coordinates is due to the rotation of the earth's inclined axis of rotation in space, a retrograde motion in relation to orbit direction.
Over the precession cycle, the Earth's north axial pole moves from where it is now pointing, within 1° of Polaris, in a circle around the ecliptic pole, with a current angular radius of 23 degrees 27 arcminutes, or about 23.5 degrees.
www.crystalinks.com /precession.html   (1033 words)

 Gyroscopic precession   (Site not responding. Last check: 2007-10-21)
Gyroscopic precession is a phenomenon occurring in rotating bodies in which an applied force is manifested 90 degrees later in the direction of rotation from where the force was applied.
Although precession is not a dominant force in rotary-wing aerodynamics, it must be reckoned with because turning rotor systems exhibit some of the characteristics of a gyro.
This correction is required because precession causes a nose down tendency and because the tilted disk produces less vertical lift to counteract gravity.
www.dynamicflight.com /aerodynamics/gyro_precess   (201 words)

In general, the term precession is used for the slow, periodic conical motion of the rotation axis of a spinning body.
The component of precession caused by the Sun and Moon acting on the Earth's equatorial bulge is called lunisolar precession, and the component caused by the action of the planets is called planetary precession.
Since the annual amount of the precession is inversely related to the obliqueness of the ecliptic plane, the derivatives of the two polynomials are expected to join at least at two abscissa points, when the ordinates are reduced to zero.
www.tenspheres.com /researches/precession.htm   (2527 words)

For a given amount of force, the rate of precession of a gyro is governed by the weight, shape, and speed of the rotor.
Precession is actually the result of two forces: angular momentum (spinning force) and the applied force (torque).
Your thumb points in the direction of the precession vector, your middle finger points in the direction of the torque vector, and your forefinger points in the direction of the spin vector.
www.tpub.com /neets/book15/63b.htm   (1435 words)

 Precession of Top
The precession angular velocity is inversely proportional to the spin angular velocity, so that the precession is faster and more pronounced as the top slows down.
Precession was caused by the gravitational torque acting on the slightly tipped, or just slightly mishapen, top - producing an "orbiting" of the top's spin angular momentum around the vertical direction.
Now, if this precession angular momentum is exactly vertical and the top is ideally balanced, there is no effect of the torque from the top's weight on it.
www.4physics.com /phy_demo/top/top.html   (850 words)

 Vector Properties of Rotational Quantities   (Site not responding. Last check: 2007-10-21)
The torque produces a change in L which is perpendicular to L. Such a change causes a change in direction of L as shown but not a change in its size.
A spinning wheel which is held up by one end of its axle will precess in the sense shown if it has that direction of spin.
The sense of precession is determined by the direction of the torque due to the weight of the spinning wheel.
hyperphysics.phy-astr.gsu.edu /hbase/rotv2.html   (254 words)

 Demo #10: Precession
If we apply a torque to the gyroscope (balance the spinning bicycle wheel on one hand, and pull a string attached to top axle with the other), it's axis of rotation does not move toward you (the direction you are pulling), but perpendicular to that so that the axis traces out a circle.
Another simple example of precession is the spinning of a top; because of variations in density of the top, its axis of rotation traces out a circle.
We can see that the Earth's axis of rotation precesses, since we know that the North Star (Polaris) was not aligned with the rotational pole in the past (it wasn't the "North Star"), and appears to be moving away from that position, so that it won't be aligned in the future.
www.geol.binghamton.edu /faculty/barker/demos/demo10.html   (627 words)

 Open Course : Astronomy : Introduction : Lecture 3 : Motion of the Earth
As the precession of the axis occurs, the orientation of the celestial equator will also change, since it is necessarily perpendicular to the axis.
Precession was discovered by the Greek astronomer Hipparchus, who had access to several centuries of Greek and Babylonian records.
Because of precession, the tropical year is 20 min 14 s shorter than the sidereal year, equal to 365.25 d - 11 min 14 s.
www.opencourse.info /astronomy/introduction/03.motion_earth   (1832 words)

 Geology 150 - Climate Changes
The axial precession is caused by the gravitational pull of the Sun and the Moon on the Earth's equatorial bulge.
The combined effect of the axial precession and precession of the ellipse is referred to as the precessional cycle with a cyclicity of 3,000 and 19,000 years (for an average of 21,700 years).
The precession cycle modifies where the equinoxes and solstices occur in the Earth's, influencing the seasonal cycle.
earth.usc.edu /~geol150/variability/orbitalchanges.html   (920 words)

 Precession of the Earth's Rotation Axis   (Site not responding. Last check: 2007-10-21)
Since the rotation axis is precessing in space, the orientation of the Celestial Equator also precesses with the same period.
This precession of the equinoxes means that the right ascension and declination of objects changes very slowly over a 26,000 year period.
Because of the precession of the equinoxes, the vernal equinox moves through all the constellations of the Zodiac over the 26,000 year precession period.
csep10.phys.utk.edu /astr161/lect/time/precession.html   (295 words)

 Why 2012?
The precession of the equinoxes, also known as the Platonic Year, is caused by the slow wobbling of the earth's polar axis.
It should be noted that because precession is a very slow process, similar astronomical alignments will be evident on the winter solstice dates within perhaps 5 years on either side of 2012.
At this point, precession and the rate of precession was calculated, the Long Count was perfected and inaugurated, and the appropriate winter solstice date in 2012 A.D. was found via the Long Count in the following way.
www.levity.com /eschaton/Why2012.html   (4477 words)

 Math & Science: precession of equinoxes
Equinoctial precession is a circular motion of the Earth's rotational axis with respect to the "fixed" stars, also known as lunisolar precession.
Since planetary precession due to perturbations from Jupiter and Saturn causes the perihelion of the Earth's orbit to precess, the precession of the Earth's axis relative to the Sun has a period of 21,000-22,000 y.
Because the Earth's rotation axis wobbles (precesses) with respect to the distant stars, so does its equatorial plane, and as a consequence the intersection of this plane with the orbital plane also moves slowly.
www.experts-exchange.com /Miscellaneous/Math_Science/Q_20612860.html   (1002 words)

 Spinning-Top Effect of PRECESSION Forces
That one is `precessing' or turning anti-clockwise because a small weight is hung on one side of its axis (or `axle' line).
This necessarily means precession is slowing - so going back in time we would find precession happening faster and faster the further back we go.
All precession - obviously - is caused by reaction to nearby masses' gravitational entanglements.
www.perceptions.couk.com /precess.html   (2604 words)

 Celestial Sphere
Precession causes the NCP to move in a circle around the North Ecliptic Pole, which changes the pole star.
As a result of precession, around 1980 the Summer Solstice crossed the modern boundary from Gemini to Taurus, which now technically holds the point.
Because the Summer Solstice is closer to the classic constellation figure of Gemini than to Taurus, and since Gemini (along with Pisces, Libra, and Sagittarius) quarters the ecliptic, Gemini is still traditionally taken as the Solstice's celestial home.
www.astro.uiuc.edu /~kaler/celsph.html#zodiac   (1937 words)

 How to Know What Your True Purpose in Life Is.
Precession is not PROcession, which means movement in a line.
Precession happens at right angles to the direction of motion.
Precession is "the effect of bodies in motion on other bodies in motion".
www.relfe.com /life_purpose.html   (5148 words)

 The Precession-Time Paradox
If precession is considered to be a physical fact, then one should also be able to measure and substantiate the additional physical time interval of more than 1223 seconds per year.
Due to the apparent precession, the measurable mean sidereal day should be about 86164.09966 seconds, since logically the actual mean rotation time of the Earth by 86164.0905382 seconds can only be measured with a delay in time relative to the inertial position of the fixed stars.
Since it was proven that a precession of the Earth cannot exist as claimed, Earth's mean sidereal rotation time of 86164.0905382 s can only coincide with one true "axis-star", which is orbited by our solar system.
www.poleshift.org /From_KHomann.html   (3568 words)

 [7.05] New Precession Formulas   (Site not responding. Last check: 2007-10-21)
We adapted J.G. Williams' expression of the precession and nutation by the 3-1-3-1 rotation (Williams 1994) to an arbitrary inertial frame of reference.
Here \gamma and \varphi are the new planetary precession angles, \psi and \epsilon are the new luni-solar precession angles, and \Delta \psi and \Delta \epsilon are the usual nutations.
Also we estimated the speed of general precession in longitude at J2000.0 as p = (5028.7955 ±0.0003)''/Julian century, the mean obliquity at J2000.0 in the rotational sense as \epsilon
www.aas.org /publications/baas/v35n4/dda2003/6.htm   (256 words)

 Learn more about Precession in the online encyclopedia.   (Site not responding. Last check: 2007-10-21)
Learn more about Precession in the online encyclopedia.
Hint: Play with putting spaces before and after your words to see the different results you get.
Precession causes the cycle of seasons (tropical year) to be about 20 minutes less than the cycle of the sun as seen with respect to the stars (sidereal year).
www.onlineencyclopedia.org /p/pr/precession.html   (1030 words)

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