<P> This concept was initially used in theories about weather prediction but later the term became a popular metaphor in science writing . </P> <P> In chaos theory, the butterfly effect is the sensitive dependence on initial conditions in which a small change in one state of a deterministic nonlinear system can result in large differences in a later state . </P> <P> The term itself was coined by Edward Lorenz, and is derived from the metaphorical example of the details of a tornado (exact time of formation, exact path taken) being influenced by minor perturbations such as the flapping of the wings of a distant butterfly several weeks earlier . Lorenz discovered the effect when he observed that runs of his weather model with initial condition data that was rounded in a seemingly inconsequential manner would fail to reproduce the results of runs with the unrounded initial condition data . A very small change in initial conditions had created a significantly different outcome . </P> <P> The idea that small causes may have large effects in general and in weather specifically was used from Henri Poincaré to Norbert Wiener . Edward Lorenz's work placed the concept of instability of the earth's atmosphere onto a quantitative base and linked the concept of instability to the properties of large classes of dynamic systems which are undergoing nonlinear dynamics and deterministic chaos . </P>

Who came up with the butterfly effect theory