born May 23, 1917, West Hartford, Conn., U.S.
U.S. meteorologist.
Following degrees from Dartmouth College and Harvard University in mathematics, he turned to weather forecasting in 1942 with the U.S. Army Air Corps. After World War II he joined MIT as a researcher, earned a doctorate in meteorology (1948), and stayed on as a professor. In the early 1960s, he discovered that the weather exhibits a nonlinear phenomenon known as sensitive dependence on initial conditions (see chaos theory ). He explained this phenomenon, which makes long-range weather forecasting impossible, to the public as the "butterfly effect": in China a butterfly flaps its wings, leading to unpredictable changes in U.S. weather a few days later.