Edward Lorenz has died at 90

Edward Norton Lorenz, the mathematician and meteorologist responsible for the term "butterfly effect" has died from cancer at age 90. A pioneer of chaos theory, Lorenz built a mathematical model of the way air moves around in the atmosphere.

As he studied weather patterns he realized that they didn't always change as predicted. Minute variations in the initial values of variables in his twelve variable computer weather model would result in grossly divergent weather patterns. This sensitive dependence on initial conditions came to be known as the butterfly effect.

Lorenz went on to explore the underlying mathematics and published his conclusions in a seminal work titled Deterministic Nonperiodic Flow, in which he described a relatively simple system of equations that resulted in a pattern of infinite complexity now known as the Lorenz attractor.

He was awarded the Kyoto Prize in 1991 and cited for "profoundly influencing a wide range of basic sciences and brought about one of the most dramatic changes in mankind’s view of nature since Sir Isaac Newton."

Lorenz is survived by daughters Cheryl, of Eugene, Ore., Nancy of Roslindale, Mass; a son, Edward of Grasse, France; and four grandchildren. His wife, Jane, died in 2001.

Dr. Lorenz remained active almost to the end of his life, in both research and outdoor activities.

“He was out hiking two and one-half weeks ago,” Cheryl Lorenz said, “and he finished a paper a week ago with a colleague.”