What specific mathematical constructs did Ptolemy introduce to explain retrograde motion in the geocentric system?

Answer

Epicycles and deferents

To account for the observed looping backward motion of planets (retrograde motion) while keeping Earth central, Ptolemy utilized epicycles (small orbits) whose centers moved along larger circles called deferents around the Earth.

What specific mathematical constructs did Ptolemy introduce to explain retrograde motion in the geocentric system?

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