The MAKE crew shows us how to build a Persistence-of-Vision (POV) gadget for your bicycle wheel. Put simply, “this projects programs LEDs to flash and appear to make words in the air.” Video after the jump. Full instructions here (PDF file).
Persistence of vision is a perceptual process where your brain holds an image in it’s head for a moment. This process is what lets us think that movies have people moving in them instead of seeing all 24 frames a second as individual pictures