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Earth's rotation axis moves with respect to the fixed stars (inertial space); the components of this motion are precession and nutation. It also moves with respect to Earth's crust; this is called polar motion. Precession is a rotation of Earth's rotation axis, caused primarily by external torques from the gravity of the Sun, Moon and other bodies.
The stars viewed from Earth are seen to proceed from east to west daily (at about 15 degrees per hour), due to the Earth's diurnal motion, and yearly (at about 1 degree per day), due to the Earth's revolution around the Sun. At the same time the stars can be observed to anticipate slightly such motion, at the rate of approximately 50 arc ...
The Eötvös effect is the change in measured Earth's gravity caused by the change in centrifugal acceleration resulting from eastbound or westbound velocity.When moving eastbound, the object's angular velocity is increased (in addition to Earth's rotation), and thus the centrifugal force also increases, causing a perceived reduction in gravitational force.
Effects of precession on the seasons (using the Northern Hemisphere terms) As the orientation of Earth's orbit changes, each season will gradually start earlier in the year. Precession means the Earth's nonuniform motion (see above) will affect different seasons. Winter, for instance, will be in a different section of the orbit.
Smaller effects also contribute to nutation. These are caused by the monthly motion of the Moon around the Earth and its orbital eccentricity, and similar terms caused by the annual motion of the Earth around the Sun.
The presence of the Moon (which has about 1/81 the mass of Earth), is slowing Earth's rotation and extending the day by a little under 2 milliseconds every 100 years. Tidal acceleration is an effect of the tidal forces between an orbiting natural satellite (e.g. the Moon) and the primary planet that it orbits (e.g. Earth).
If the motion is damped, the oscillations will die down until the motion is a steady precession. [3] [4] The physics of nutation in tops and gyroscopes can be explored using the model of a heavy symmetrical top with its tip fixed. (A symmetrical top is one with rotational symmetry, or more generally one in which two of the three principal ...
He also calculated the effect of precession on movement of the heavenly bodies. [6] [7] [8] The apsidal precessions of the Earth and other planets are the result of a plethora of phenomena, of which a part remained difficult to account for until the 20th century when the last unidentified part of Mercury's precession was precisely explained.