In physics, there are two types of precession: torque-free and torque-induced.

When an object is not perfectly solid, internal vortices will tend to damp torque-free precession, and the rotation axis will align itself with one of the inertia axes of the body.

Another type of torque-free precession can occur when there are multiple reference frames at work.

As a consequence, an accurate measurement of the earth ’ s axial reorientation relative to objects outside the frame of the moving galaxy ( such as distant quasars commonly used as precession measurement reference points ) must account for a minor amount of non-local torque-free precession, due to the solar system ’ s motion.

* Possible motions in the absence of external forces are translation with constant velocity, steady rotation about a fixed principal axis, and also torque-free precession.

In this cases we can have torque-free precession.

For the RHSs equal to zero there are non-trivial solutions: torque-free precession.

In this cases we will have torque-free precession, in such a way that I ( t ) and ω ( t ) change together so that their derivative is zero.

Notice that this equation for R has a solution only if the sum of the individual torques on the right side yield a vector that is perpendicular to F. Thus, the condition that a system of forces has a torque-free resultant can be written as

The rate of precession is related to the tilt by

The gradual depletion of the Kuiper belt would have decreased the precession rate of Neptune's orbit ; eventually, the frequencies matched, and Saturn's axial precession was captured into the spin-orbit resonance, leading to an increase in Saturn's obliquity.

The Titan Ringlet within Saturn's C Ring represents another type of resonance in which the rate of apsidal precession of one orbit exactly matches the speed of revolution of another.

** The solid angle or the rate of precession in a gyroscope.

where is the precession rate, is the spin rate about the axis of symmetry, is the angle between the axis of symmetry and the axis about which it precesses, is the moment of inertia about the axis of symmetry, and is moment of inertia about either of the other two perpendicular principal axes.

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 ( in particular, his General Theory of Relativity ), which accurately predicted the anomalies.

The Tropical zodiac ( of Mesopotamian origin ) is divided by the intersections of the ecliptic and equator, which shifts in relation to the backdrop of fixed stars at a rate of 1 ° every 72 years, creating the phenomenon known as precession of the equinoxes.

where θ is the angle between the vectors Ω < sub > P </ sub > and L. Thus, if the gyroscope's spin slows down ( for example, due to friction ), its angular momentum decreases and so the rate of precession increases.

The difference is caused by the precession of the equinoxes, and means that over long periods of time a calendar based on the sidereal year will drift out of sync with the seasons at the rate of about one day every 72 years.

At the same time the stars can be observed to move slightly retrograde, at the rate of about 50 arc seconds per year, a phenomenon known as the “ precession of the equinox ".

Hipparchus concluded that the equinoxes were moving (" precessing ") through the zodiac, and that the rate of precession was not less than 1 ° in a century, in other words completing a full cycle in no more than 36000 years.

Nonetheless, they kept accurate calendars and if they recorded the date of the temple reconstructions it would be a fairly simple matter to plot the rough precession rate.

He estimated the rate of precession as 1 ° in 50 years ( Pannekoek 1961, p. 92 ).

Comparing this with the length of the sidereal year, he calculated that the rate of precession was not less than 1 ° in a century.

For that it is assumed that the precession rate is proportional to the projection of the angular velocity of Earth onto the normal direction to Earth, which implies that the plane of oscillation will undergo parallel transport.

This idea inspired Thābit ibn Qurra in the 9th century to create the theory of trepidation to explain a variation which he ( incorrectly ) believed was affecting the rate of precession.

However, torque is proportional to rate of change of angular momentum, so precession occurs: the direction of spin changes.

Of several proposed shape models that agreed with the images, a " snowman "- like shape was found to best fit the observed precession rate of Hermione's satellite.

The disk, when spun on the mirror, exhibits a spinning / rolling motion ( or spolling, a blend of " spin " and " roll "), slowly moving through different rates and types of motion before coming to rest – for example, the precession rate of the axis of symmetry accelerates as the disk spins down.

In fact, precession rate of the axis of symmetry approaches a finite-time singularity modeled by a power law with exponent approximately − 1 / 3 ( depending on specific conditions ).

Experiments show that rolling friction is mainly responsible for the dissipation and behavior – experiments in a vacuum show that the absence of air affects behavior only slightly, while the behavior ( precession rate ) depends systematically on coefficient of friction.

Equation ( 24 ) of the article Orbital perturbation analysis ( spacecraft ) gives the precession rate of an orbit around an oblate planet as

Torque-free precession occurs when the axis of rotation differs slightly from an axis about which the object can rotate stably: a maximum or minimum principal axis.

Torque-induced precession ( gyroscopic precession ) is the phenomenon in which the axis of a spinning object ( e. g., a part of a gyroscope ) " wobbles " when a torque is applied to it, which causes a distribution of force around the acted axis.

A combination of lunar gravity, solar gravity, and the flattening of the Earth at its poles causes a precession motion of the orbital plane of any geostationary object, with a period of about 53 years and an initial inclination gradient of about 0. 85 degrees per year, achieving a maximum inclination of 15 degrees after 26. 5 years.

Le Verrier postulated that the excess precession could be explained by the presence of a small planet inside the orbit of Mercury, and he proposed the name " Vulcan " for this object.

They pointed out that astrologers have only a small knowledge of astronomy and that they often do not take into account basic features such as the precession of the equinoxes which would change the position of the sun with time ; they commented on the example of Elizabeth Teissier who claimed that " the sun ends up in the same place in the sky on the same date each year " as the basis for claims that two people with the same birthday but a number of years apart should be under the same planetary influence.

The tropical zodiac has no connection to the stars and avoids the issue with precession moving the constellations as long as they make no reference to the constellations themselves being in the associated zodiacal sign.

Due to the precession of the equinoxes the December solstice no longer takes place while the sun is in the constellation Capricornus, as it did until 130 BCE, but the astrological sign called Capricorn begins with the solstice.

The orientation of the Earth's axis and equator are not fixed in space, but rotate about the poles of the ecliptic with a period of about 26, 000 years, a process known as lunisolar precession, as it is due mostly to the gravitational effect of the Moon and Sun on the Earth's equatorial bulge.

This adds a periodic component to the position of the equinoxes ; the positions of the celestial equator and ( vernal ) equinox with fully updated with precession and nutation are called the true equator and equinox ; the positions without nutation are the mean equator and equinox.

Currently about 23 °. 4, it varies slightly due to motion of the plane of the Earth's orbit, and hence the ecliptic, with planetary precession.

However, due to the precession of the equinoxes, June begins with the sun in the astrological sign of Gemini, and ends with the sun in the astrological sign of Cancer.

The location of the Prime Meridian as well as the position of body's north pole on the celestial sphere may vary with time due to precession of the axis of rotation of the planet ( or satellite ).

Relativistic effects cease to be negligible when near very massive bodies ( as with the precession of Mercury's orbit about the Sun ), or when extreme precision is needed ( as with calculations of the orbital elements and time signal references for GPS satellites.

One disadvantage of these names is that, due to the precession of the equinoxes, the astrological signs where these solstices are located no longer correspond with the actual constellations.

These mark the movement of the Sun along a sidereally fixed zodiac ( precession is ignored ) into Makara, the zodiacal sign which corresponds with Capricorn, and into Karkat, the zodiacal sign which corresponds with Cancer, respectively.

In Hamlet's Mill, co-authored with Hertha von Deschend, the authors find that the sampo or precession process was believed to grind out different world ages, from dark age to golden age and back again over the long precession cycle.

The Babylonian calendar as it stood in the 7th century BC assigned each month to a sign, beginning with the position of the Sun at vernal equinox, which, at the time, was depicted as the Aries constellation (" Age of Aries "), for which reason the first sign is still called " Aries " even after the vernal equinox has moved away from the Aries constellation due to the slow precession of the Earth's axis of rotation.

Precession can be demonstrated by placing a spinning gyroscope with its axis horizontal and supported loosely ( frictionless toward precession ) at one end.

Instead of falling, as might be expected, the gyroscope appears to defy gravity by remaining with its axis horizontal, when the other end of the axis is left unsupported and the free end of the axis slowly describes a circle in a horizontal plane, the resulting precession turning.