This is the season of Hollywood's unrestrained id: the brainless summer blockbuster, the air-conditioned multiplex, the bottomless popcorn refills, the avalanche of kids emerging blinking into bright sunlight, waiting for their parental pickup. But August is also the anniversary of the movies themselves! It was on August 31, 1897 that Thomas Edison patented his first movie camera, the Kinetograph. In honor of 119 years of cinematic glitz and glamour, we've asked movie buff and Jeopardy! tough Ken Jennings to give us the "reel" truth on all kinds of old-movie misinformation.
The Debunker: Do Movies Work Through "Persistence of Vision"?
Nearly every work on film theory begins with one starting principle: that the illusion of motion in motion pictures is only possible through a phenomenon called "persistence of vision." This was a turn-of-the-century attempt to explain the miracle that makes cinema possible: images flash on a screen, and even though they don't move, our brain believes they do. Psychologists decided that something called "persistence of vision" must be involved: some kind of retinal after-image in the eye itself weaves the still images together into a moving whole.
But news flash: an Austrian scientist named Max Wertheimer used a series of flickering light experiments to disprove the after-image "persistence of vision" theory. "It is not sufficient to draw upon pure peripheral processes in relation to a single eye," he wrote. "We must have recourse to processes which lie behind the retina." The real eye-opener here is that Wertheimer's experiments happened in 1912. That's right: the term "persistence of vision" is still bandied about by the public and even taught in film schools, when it was discredited over a century ago! More like "persistence of bad science."
So: when we sit in a theater watching Indiana Jones or Captain America leap into action, how do we human beings overcome the flicker of a projector and link those still images into motion? Well, as Wertheimer discovered, this is a miracle that happens in the brain, not in the eye. The process is complicated, and combines vision processing in two different parts of the brain, one in charge of determining where things are, and another in charge of tracking what they are. In simple terms, the brain is repeatedly checking in with visual input from the eyes, noting what's changed since the last update, and registering that as "motion." Remember that, even outside the movies, we're always moving our eyes around, seeing things in quick glimpses, not always catching the full story but intuiting important connections. To the brain, the act of experiencing real life also comes in brief temporal chunks not too different from the 24 frames a second of the multiplex.
Quick Quiz: Who was inspired by a melting wheel of Camembert cheese to create his 1931 masterpiece The Persistence of Memory?
Ken Jennings is the author of eleven books, most recently his Junior Genius Guides, Because I Said So!, and Maphead. He's also the proud owner of an underwhelming Bag o' Crap. Follow him at ken-jennings.com or on Twitter as @KenJennings.