1、
The orbits of planets in the once popular geocentric Ptolemaic system are epitrochoids.
曾经盛行的托勒密地心说体系里的行星轨道就是外旋轮线.
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2、
Text at the upper right explains the movement of the planets according to the Ptolemaic system.
右上角的文字解释了托勒密系统的行星运动.
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