Today, Saturn, as seen from Earth, will appear stationary in the sky and will begin its retrograde motion tomorrow. While not as obvious as, say, Mars, Saturn also appears to move with the stars, slow down, stop, and then begin to move counter to the background stars just like the Red Planet does. Why? It's an optical illusion caused by the faster Earth passing the slower Saturn. The same thing happens when you pass a slower car on the freeway when the car you pass appears to be falling behind you even though both are actually moving forward. The same is true of planets.