Porpidia flavocaerulescens, orange boulder lichen, photographed in Alaska by Steve and Sylvia Sharnoff, whose beautiful lichen sampler and gallery are taken from their book, Lichens of North America. (thanks to Anne Galloway for the link)
I never thought too much about the old adage that you can’t fold a piece of paper in half more than 7 times; I tried with a couple of different pieces of paper, couldn’t do it, and stopped there, except for a vague idea that I could do better with a much bigger piece of paper. Not Britney Gallivan, whose elbows you see there on a piece of paper folded 11 times (she’s since managed 12). She derived expressions to describe the folding limits for one direction (L = (π.t/6)(2n + 4)(2n – 1), where L = length and t = thickness of the material and n is the number of folds) and alternating directions (roughly W = π.t.23(n-1)/2), then demonstrated the validity of her equations with gold foil and then with paper. Another approach is described here on Math Forum, or you can buy Ms Gallivan’s booklet. I wish I’d had her chutzpah, not to mention her smarts, when I was in high school.