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Kepler

A portrait depicts a man with curly hair and a full beard, wearing a brown robe over a dark shirt, set against a dark background.

German astronomer Johannes Kepler (1571–1630). His three laws of planetary motion — published between 1609 and 1619 — were the first quantitative account of why the planets appear to slow down, speed up, and double back across the sky. The Antikythera Mechanism's pin-and-slot gearing models exactly this irregular motion, mechanically, sixteen centuries before Kepler explained it mathematically.

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