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In astronomy, axial precession is a gravity-induced, slow, and continuous change in the orientation of an astronomical body's rotational axis. In the absence of precession, the astronomical body's orbit would show axial parallelism. [2] In particular, axial precession can refer to the gradual shift in the orientation of Earth's axis of rotation ...
The torque-free precession rate of an object with an axis of symmetry, such as a disk, spinning about an axis not aligned with that axis of symmetry can be calculated as follows: [1] = where ω p is the precession rate, ω s is the spin rate about the axis of symmetry, I s is the moment of inertia about the axis of symmetry, I p is moment ...
Axial precession is the trend in the direction of the Earth's axis of rotation relative to the fixed stars, with a period of about 25,700 years. Also known as the precession of the equinoxes, this motion means that eventually Polaris will no longer be the north pole star .
The geographic poles are defined by the points on the surface of Earth that are intersected by the axis of rotation. The pole shift hypothesis describes a change in location of these poles with respect to the underlying surface – a phenomenon distinct from the changes in axial orientation with respect to the plane of the ecliptic that are caused by precession and nutation, and is an ...
For a rigid Earth which is an oblate spheroid to a good approximation, the figure axis F would be its geometric axis defined by the geographic north and south pole, and identical with the axis of its polar moment of inertia. The Euler period of free nutation is (1) τ E = 1/ν E = A/(C − A) sidereal days ≈ 307 sidereal days ≈ 0.84 ...
At present, the rate of axial precession corresponds to a period of 25,772 years, [3] so sidereal year is longer than tropical year by 1,224.5 seconds (20 min 24.5 s, ~365.24219*86400/25772). Before the discovery of the precession of the equinoxes by Hipparchus in the Hellenistic period , the difference between sidereal and tropical year was ...
In the principal axis frame (which is rotating in absolute space), the angular momentum vector is not conserved even in the absence of applied torques, but varies as described by Euler's equations. However, in the absence of applied torques, the magnitude L {\displaystyle L\ } of the angular momentum and the kinetic energy T {\displaystyle T ...
A pure nutation is a movement of a rotational axis such that the first Euler angle is constant. [citation needed] Therefore it can be seen that the circular red arrow in the diagram indicates the combined effects of precession and nutation, while nutation in the absence of precession would only change the tilt from vertical (second Euler angle).