Daniel Shiffman’s book entitled, The Nature of Code, discusses how the open source programming language Processing can be used to create computer simulations of natural systems. Keeping with the open source spirit, the entire text of the book is freely available at the book’s website (natureofcode.com). If you’re not feeling up to reading the entire book, the accompanying app for the iPad/iPhone is a great introduction to some of the mathematical concepts and systems found in the natural world. The app includes interactive simulations of these concepts/systems, which are organized into eight categories: randomness, vectors and forces, oscillation, particle systems, triangulation, hair, evolution, and steering. Example simulations include one in which users watch as a tank full of “beings” procreate when they touch (an example of evolution), as well as a simulation of wave addition in which users can drag their fingers to change the amplitude and frequency of one of the waves.