![]() The physical cause of the precession is a torque (twisting) of theĮarth, caused mostly by the sun's and the moon's gravity pulling Vega willīe our north star for a time in the distant future.Īnother consequence is that precession introduces a difference betweenĪ sidereal (real) year and a tropical (by the sun) year becauseĭuring the course of one year the position of the equinox changes It is only "north star" by coincidence today. One consequence of precession is that the north star Polaris isĭrifting. In this wobble motion, the tilt of the earth stays roughly constant atĢ3.4 degrees but the orientation is always changing. To a gyroscopic wobble of earth's spin axis that takes 26000 years to The stars than the 150-year-old comparison charts showed. Path crosses the celestial equator) were in a different position among What he saw was that the equinoxes in his day (where the sun's Hipparchus when he compared his own circa 200 BC records with olderĬharts. The phenomenon we call "precession" was discovered by Greek astronomer ![]() Astronomy: precession of earth Astronomy: precession of earth
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