February 24, 2020. The computational power of a humble napkin is awesome. I discuss three napkin algorithms — dimensional analysis, Fermi estimates, and random walks — and use them to figure out why rain falls, the length of the E. coli genome, and the mass of a proton, among other things. These examples suggest a napkin-based approach to teaching physics. Contents Hacking physics Dimensional analysis Pendulous pumpkins Drag and drop Usage notes Fermi estimates Geometric means Subestimates KISS ...