Then, for the next two months, Mars will reverse its course in the heavens and will move backward against the star background - toward the west - almost as if it had lost something. Then, on Dec. 10, it will pause again, before resuming its normal eastward movement.
Puzzling the ancients
All the planets exhibit this "retrograde motion" at one time or another. But for the longest time, the ancient astronomers were unable to come up with a satisfactory explanation for it.
For one thing, while behaving in this strange manner, Mars will also appear to deviate somewhat from its normal course; the retrograde motion will appear to bring it a little below its regular orbital track. In other words, for those of us watching from Earth, Mars will appear to travel in a loop.
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