Wobble Lecture.docx

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Earth, Space Science and Engineering
ESSE 3020
Anthony Anthony

Wobble The Earth's wobble is typically known as the Chandler wobble. 305 days is the period for a rigid Earth. -435 is for the real observed Earth. -Earth is not a solid, there is a part that is fluid. This fluid is responsible for the difference. -The fluid core in the rigid shell alters the wobble period of Earth. The fct that the Earth can deform makes it responsible for this property. -Due to pole tides, there is inelasticity in the mantle. The pole tide brings it up to a few days(8 days) -There is a ring of stars above the North Pole. -The path given is a beating of two wobbles-Chandler and Annual wobble. The chandler wobble has a certain magnitude. If there was no annual wobble, we would expect the path to come back to the same place after 435 days. Due to annual wobble, over 12 months, it isnt quite back to the same place. 12 months and 14 months, the LCM is ~70 months(12 months and 14 months, common multiple is 6 years) -If we traced a path starting from Sept 1980, 14 months later it goes around and comes back and back to a certain point. -The magnitude of chandler wobble is 0.015 milliarc s. -The annual wobble magnitude is 0.10 arc seconds. -Due to the two different periods and amplitudes, they superimpose. -Going to the reconciliation between theoretical and observed, we know the wobble formula for rigid Earth. 1/wobble is one day. -The time rate of change of angular momentum=torque. -In the case of free wobble, there is no external torque. Forced wobble has an external torque. -The angular momentum vector remains fixed in space. One cone has a symmetry axis of x3. -A nutation is seen in space. -Body vector and rotation axis are always coplanar. -nu not is a small angle, but in b) it i
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