Edward Norton Lorenz (May 23, 1917 – April 16, 2008) was an American mathematician and meteorologist. He was one of the first to work in the field of Chaos theory. He was the first to use the term Butterfly effect for dynamic systems that are very sensitive to starting conditions. In the 1960s, he used a simple model for weather prediction, which he simialated on a computer. With this setup, he discovered that only a slight change of the values he used for the model could lead to totally different results. This is known as Butterfly effect. In numerical weather predicion, values are often rounded, so that in each step, a small error is added.