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Ptolemaic system




A theory, developed by Ptolemy about 150 AD, in which a motionless Earth is said to be at the center of the universe with the Sun, Moon, and planets revolving around it in eccentric circles and epicycles; the fixed stars are attached to an outer sphere concentric with Earth. The Ptolemaic system gave the positions of the planets accurately enough for naked-eye observations, although it also made some ridiculous predictions, such as that the distance to the Moon should vary by a factor of two over its orbit. It held sway in Europe, supported by the Church of Rome, until the rise of the Copernican system.


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