Who Travels Backwards

“One of the nicknames given to Mars by the ancient Egyptians was sekded-ef em khetkhet, which means “who travels backwards,” a clear reference to its apparent retrograde motion. It was mysterious to the early observers, but with our current understanding we know that this retrograde motion is entirely an illusion caused by the Earth passing the slower moving Mars, which has a larger orbit. 
Image credit: Cenk E. Tezel & Tunc Tezel
Animation credit: Eugene Alvin Villar

Via Phroyd.tumblr.com