Daily #12: Ptolemaic
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In Ptolemy's time, astronomers thought planets orbited as smaller circles within a larger circle. A rotating circle on the edge of a rotating circle. This sketch visualizes that.
Seven circles orbit around the center. (7 planets were known in Ptolemy's time.) Each little circle has a small planet orbiting around the little circle. A line is drawn from where the planet is to the center. When the planet is closest to the center, the line is white. When it's farthest, it's black.
by Cory Barr. Dec 11, 2015