Edward Lorenz, 90, Father of Chaos Theory

Edward Lorenz, the father of chaos theory, died yesterday at his home in Cambridge, Mass., Wednesday. He was 90.

As a professor at the Massachusetts Institute of Technology, he came up with the scientific concept that small effects lead to big changes, something that was explained in a simple example known as the "butterfly effect." He explained how something as minuscule as a butterfly flapping its wings in Brazil changes the constantly moving atmosphere in ways that could later trigger tornadoes in Texas.