Because I max, I int, and I min are orthogonal, the simple interchange case (with no independent plate motions) yields a 90° shift. This would result in a rapid movement away from the spin axis by the geographic location of the former pole with rotation of the entire solid Earth centered about the minimum moment of inertia (I min) located on the equator. Evans, Evidence for a Large-Scale Reorganization of Early Cambrian Continental Masses by Inertial Interchange True Polar Wander, Science 277:5325 pp 541-545 (1997), doi: 10.1126/science.277.5325.541Ī variant of this mechanism, inertial interchange true polar wander (IITPW), involves discrete bursts of TPW of up to 90° in geologically short intervals of time if the magnitudes of the intermediate (I int) and maximum (I max) moments of inertia cross (36). There are signs that the Earth has undergone significant true polar wander. You rounded up, you forgot that increasing the C (polar) moment of inertia necessarily decreases at least one of the other two moments, and you used ice rather than rock. ![]() Considering that 2 polar caps, each with a thickness of 1 km and a radius of 1000 km is only 6.3 x 10 6 cubic km, such a scenario is extremely unlikely. This is equivalent to moving about 7.5 x 10 18 metric tons (7.5 x 10 9 cubic km) of water from the equator to the poles as an ice cap. There are also articles arguing against such events.Ī necessary (but not sufficient) prerequisite for an Earth pole reversal without changing the angular momentum vector is reducing the moment of inertia about the C (polar) axis by about 3 x 10 35 kg-m 2. There are several articles in the scientific literature arguing for various true polar wander events. Whether true polar wander ever did occur remains a bit contentious. This is a very slow process, a degree or so per million years. ![]() It is the continents, and possibly the mantle, that wander. The Earth's rotation axis when viewed from an inertial frame doesn't wander. True polar wander results when the mantle changes orientation. Apparent polar wander results from the motion of the tectonic plates. There is a phenomenon called polar wander, but this does not involve the earth spinning in the opposite direction. The magnitude of the wobble oscillates, alternately damped and excited by the polar tide. The Chandler wobble doesn't have quite the frequency one would expect for a rigid symmetric top. This makes the behavior deviate from that of a rigid body. The large scale tumbling seen in that video becomes a tiny little thing called the Chandler wobble with the Earth. Moreover, the ratio (C-A)/C is about 1/309. The Earth is very close to a symmetric top the ratio (B-A)/C is very, very tiny. The intermediate unstable axis B has an moment of inertia that is just about ideally placed in terms of maximizing tumble. Labeling the principal moments of inertia as A, B, and C, with A ![]() Read ".First there is a real retardation of the Moon's angular rate of orbital motion, due to tidal exchange of angular momentum between the Earth and Moon. When the Earth's rotation slows due to tidal forces, down, the Moon's angular momentum increases due to tidal forces, and moves to a higher orbit. An observer in space would say that the Earth's tides did not change direction, but would say that the north and south poles flipped.īy the way, the vector sum of the Earth's and Moon's angular momentum is conserved. If the Earth's angular momentum is unchanged, and the Earth's body axis flipped say over in a year (365 revolutions), an observer on Earth would see the east→west direction of the tides change by ~3 degrees per day to west→east. Someone earlier said the tides of the ocean would change the Moons orbit.
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