retrograde motion

“…[S]ince Earth completes its orbit in a shorter period of time than the planets outside its orbit [including Jupiter], we periodically overtake them, like a faster car on a multi-lane highway. When this occurs, the planet we are passing will first appear to stop its eastward drift, and then drift back toward the west. Then, as Earth swings past the planet in its orbit, it appears to resume its normal motion west to east.” See, Wikipedia, “Retrograde and Direct Motion” (accessed 12/18/08).