History of Astronomy Demonstration [Go Back to Lecture] [Class Home Page]

The term 'planets' comes from the Greek word for `wanderers', because these bright objects appeared to be moving along the stars (though always staying along the ecliptic!). But what was most bizarre, is that the planets would be seen, over a period of several weeks, to slow down in their motion, stop, move backwards for a while, then continue back in their normal easterly motion against the stars. This was called Retrograde Motion.

To see the demonstration of retrograde motion of Mars below, click RELOAD on your browswer and the animated gif will restart again.



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