Page:The Gradual Acceptance of the Copernican Theory of the Universe.djvu/18

 Thus our heritage in astronomical thought, as in many other lines, comes from the Greeks and the Romans reaching Europe (in part through Arabia and Spain), where it was shaped by the influence of the schools down to the close of the Middle Ages when men began anew to withstand authority in behalf of observation and were not afraid to follow whither their reason led them.

But not all Greek philosophers, it seems, either knew or accepted the Babylonian cosmology. According to Plutarch, though Thales (640?-546? B. C.) and later the Stoics believed the earth to be spherical in form, Anaximander (610-546? B. C.) thought it to be like a "smooth stony pillar," Anaximenes (6th cent.) like a "table." Beginning with the followers of Thales or perhaps Parmenides (?-500 B. C.), as Diogenes Laërtius claims, a long line of Greek thinkers including Plato (428?-347? B. C.) and Aristotle (384-322 B. C.) placed the earth in the center of the universe. Whether Plato held that the earth "encircled" or "clung" around the axis is a disputed point; but Aristotle claimed it was the fixed and immovable center around which swung the spherical universe with its heaven of fixed stars and its seven concentric circles of the planets kept in their places by their transparent crystalline spheres.

The stars were an even greater problem. Anaximenes thought they were "fastened like nails" in a crystalline firmament, and others thought them to be "fiery plates of gold resembling pictures." But if the heavens were solid, how could the brief presence of a comet be explained?

Among the philosophers were some noted as mathematicians whose leader was Pythagoras (c. 550 B. C.). He and at least one

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