Butterfly effect

The exquisite sensitivity of the outcome of a system in chaotic motion on initial conditions. A small change in the measurement or assumed starting point of a system in chaos may produce large variations in the long-term behavior of the system. Even very simple systems can be chaotic: the requirements are non-linearity and feedback. The term butterfly effect comes from the work of Lorenz, who in a 1963 paper for the New York Academy of Sciences noted, "…one flap of a seagull's wings could change the course of weather forever." The poetic butterfly came later.