Original film · Math
Why can't you fold paper more than seven times? Explained
Every fold doubles the thickness, and each fold's curved edge eats paper. See how Britney Gallivan folded a kilometer-long strip 12 times, and how far 42 folds would reach.
Transcript
Why is it so hard to fold paper more than seven times? Every fold doubles the thickness. One sheet becomes two layers, then four, then eight. Seven folds make a hundred twenty-eight layers, as thick as a notebook. But thickness is only half the problem. Each fold has to wrap the whole stack around a curved edge, and that curve eats up paper. The thicker the stack, the more length each fold costs, so the sheet runs out fast. A high school student, Britney Gallivan, worked out how much length each fold needs. Then, in two thousand two, she folded a single strip of paper in half twelve times. The strip was more than a kilometer long. Now stretch the sheet. Twelve folds of office paper need nearly a kilometer. Thirteen need about four times that. So seven isn't a law of nature. It's what an ordinary sheet allows. And if you could keep going? After forty-two folds, a sheet of paper would reach past the Moon. Try it yourself at Explainer Tools dot com.