I don't blame you, kamamer, for propogating this myth, but the "butterfly flaps its wings in China" explanation is a load of crap invented by Michael Crichton in order to sell more books. (Jurassic Park)

The real story: The name "butterfly effect" comes from the image of two graphs. A scientist, working on a weather modeling program, decided to go out for lunch in the middle of a simulation. Before he turned the computer off, he wrote down all the values in the system. (They didn't have nifty things like hard drives in those days). But he when he came back, he only entered each value to two significant digits, while the computer worked in four or five. The results of the simulation were much different from what he had expected. He traced the error back to entering imprecise numbers. He went back and ran the sim again with five significant digits. Then he compared the two graphs. At first, they appeared to be almost identical, then one began to diverge. Eventually, they were so far out of synch that the graph looked like butterfly's wings. That's where the name comes from.

This is also known as sensitive dependence on initial conditions.

I might add that Edward Lorenz discovered this phenomenon and coined the term in 1961 while working on computer weather simulations. When he made slight changes in the initial conditions that he entered, the resulting weather conditions were very different. He was first to describe this deterministic chaos as the shaper of weather.

There is a short story by Ray Bradbury called A Sound of Thunder. It concerns time travel, and a company that offers this service to big game hunters.

Much care is taken care to allow the killing of dinosaurs that are about to die, no others--so not to affect the future, our present.

However, one hunter, accidentally, steps upon a butterfly. When he arrives back--all is changed.

This story dates to the late 40's, I think. Is this a case where the creative imagination prefigures the scientific intellect?

Can it be possible, that at the furthest reaches of the knowable, it is not science that leads--or the desire to control--but imagination--the desire to create?

This has also be dramatised in the Ray Bradbury Theatre, a television program.

      Artful Dodger: That is correct, however the weather effect is derived from this. In any non-linear (derived system), a small change in a variable can cause a massive shift in the end result. The global weather system is best represented as a derived equation with as many terms as you wish to consider. IANAM, but if the pressure exerted by a butterfly's wings is expressed in respect to time/temperature/whatever, the factor will be multiplied and influence anything after it. This was proven by the scientist (I forgot his name, but he worked at Berkeley) and the shift in his graph.

It is trivial whether it looked like a butterfly, smurph or bell curve at the end - what matters is that the graph shifted more and more over time as the 'mistake' was amplified by anything that was calculated with it later on. Hence, the butterfly doesn't exaclty cause a snowstorm in Canada, but it might shift it considerably. That's why, btw, we can't predict the weather for more than a few days at a time - there are too many small factors we can't consider that end up shifting it in the big picture (Airplanes, Cars, butterflies ^_^)

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