The effect is called "persistence of vision". Scan lines in early television also relied on this effect to create a perceived solid image from a "flying spot".

I saw one of these red-orange giant rubber bouncy balls roll past me on a windy night. It was moving FAST. I chased it on my bike into the camp area and brought it over to the Hookahdome where I just rolled it into the crowd. A little raver girl spotted it first and started playing with it and she s...