Demystifying the butterfly effect

Can a butterfly flapping its wings in Brazil cause a tornado in Texas? Scientists and meteorologists have been grappling with this curious conundrum for the past four decades.

Professor Etienne Ghys, 53, director of research, CNRS, France, was at the Tata Institute of Fundamental Research (TIFR) recently to deliver a lecture on the complicated and fascinating phenomenon called the butterfly effect.

Explaining what the effect is, Ghys said the sensitivity to initial conditions, which may result in a huge difference in the final conditions, is reflected in the butterfly effect.

Edward Lorenz, a physicist and a meteorologist in the early 1960s, was perplexed by this sensitivity. “While studying the weather phenomenon, Lorenz was struck by the effect the change in initial conditions has on the final result,” said Ghys. Lorenz’s postulate on the butterfly effect has crucial consequences in chaos theory.

Lorenz made another important observation regarding the weather. “He mentioned that minuscule disturbances neither increase nor decrease the frequency of occurrence of various weather events.

They only make some modification,” Ghys said. Hence, the sensitivity of initial conditions should not prevent us from predicting the weather. “We don’t care if the molecule that triggered a tornado comes from Brazil or Singapore. What matters to us is the prediction of the storm,” he said.

Ghys said the problem hasn’t been entirely resolved, however. “One school of thought believes in the importance of initial conditions, while others think that in the final picture, it is the macroscopic and not the microscopic view that matters,” he said.

Talking on the popularity of the effect, he said minor acts in the past having a huge impact on the present was the
subject of a recent Hollywood movie.

Ghys concluded that while understanding the effect is a big challenge, it provides for an interesting interchange between mathematics and the physical world.