Edward Lorenz, meteorologist and founder of chaos theory, passed away today at the age of 90. He discovered the chaotic properties of nonlinear systems as a result of an unexpected result while running numerical weather simulations in 1961, and changed the way we think about complex systems.
For those of you with a mathematical background, I recommend taking a look at his 1963 paper “Deterministic Nonperiodic Flow,” in which he proves one of the most basic results of chaotic dynamics (that nonperiodic flows are unstable against small perturbations), applies it to a simple problem in fluid dynamics, demonstrates vividly and in pictures the way that the system becomes unpredictable, and reflects on its significance for weather prediction. It seems a fitting way to mark his passing, and the paper is great; very straightforward1 and well-written, and full of the best pictures that 1963-era computing could produce.
1 By comparison to most technical papers in mathematics, that is, and especially to most papers on differential equations. I realize that this is not the best definition of “straightforward.”