History of Dharmashastra (Ancient and Mediaeval Religious and Civil Law in India) v6.c82.632

v6.c82.632

⁹⁸⁷ Besides the two motions of the earth (viz its daily revolution on its own axis and its yearly revolution round the sun) there is a third motion which is not so well-known. The earth is not a sphere, its equatorial diameter being longer than its polar diameter. The result is that there is a mass of matter bulging out at the equator which is in excess of what it would be if the earth were perfectly spherical. The earth's axis has a slight conical wobbling motion like that of a toy top and it describes a cycle in about 25800 years, the yearly shift being about 50"-2 seconds, due to the pull of the sun and the moon on the equatorial bulge. This causes the appearance of the fixed stars and even the pole-star changing their positions from century to century or from period to period Vide Sir Norman Lockyer's 'Dawn of astronomy' pp. 124-128, Van Den Bergh in 'Universe in Space and Time' p. 82, Hickey's 'Introducing the Universe' p. 117