eer, George Birkoff (1922), was computing the output of a very reduced subset of Saltzman’s differential equations for predicting the weather (1962). Lorenz found that numerically integrated trajectories manifested unpredictable times and directions of motion between the two spiral orbits of what has come

ter — they are just chaotic. Four Body Problem Butterflies and Sliding Doors After Poincaré, the field of chaos remained fairly quiet until Edward Lorenz began studying weather patterns using computers in the 1960s. The story goes, one day his computer was misbehaving and he had to re- key some data in

MARTIN,HARRIET G ELLIOT IV,WALTER J LORENTZEN,MATTHEW B GWYNNE,JAY M R H TRUST

impressed me mightily. They still do. One is Konrad Lorenz’s On Aggression. An M.D. and a Ph.D. and a 1973 Nobel laureate in medicine and physiology, Lorenz established the field of ethology, the study of the behavior of animals within their natural environment. In his prologue to On Aggression, Lorenz wr