The two periodic parts are a more or less circular motion called Chandler wobble with a period of about 435 days, and a yearly circular motion.
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This polar motion should not be confused with the changing direction of the Earth's spin axis relative to the stars with different periods, caused mostly by the torques on the Geoid due to the gravitational attraction of the Moon and Sun.
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Albrecht was one of the founders of the International Polar Motion Service, predecessor to the International Earth Rotation and Reference Systems Service, and one of the co-founders of the fraternity in 1861.