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The theory that the earth lies at the centre of the universe belongs to Greek scientific astronomy. The first man to whom the notion that the earth is spherical and lies at the centre of a spherical universe is credibly attributed is Parmenides (early 5th cent.). By the time of Eudoxus (c.360) the standard view was that the stationary spherical earth lies at the centre, around which rotates the outermost sphere of the fixed stars, once daily about the poles of the equator, carrying with it the intermediate spheres of the other heavenly bodies (also centred on the earth, but rotating in the other sense about different poles). That is the basis of Aristotle's picture of the world, which dominated the cosmology of antiquity and the Middle Ages. Acc. to this, the sublunar region is composed of the four mutable elements, earth, air, fire, and water, whose natural motion is in a straight line, i.e. ‘down’ towards the earth, or ‘up’ away from its centre. Everything above that region (including the visible heavenly bodies) is composed of an immutable ‘fifth element’ whose natural motion is circular. See aristarchus 1.

Subjects: Classical Studies — Physics.

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