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Sunday, April 20, 2008

Could a butterfly in Brazil cause a twister in Texas?

That’s what meteorologist Edward Lorenz postulated in his 1972 paper on predictability of weather. Lorenz, who died last week at the age of 90, used this example to illustrate his “chaos theory,” which linked small changes in a system to large, unforeseen consequences. For more background on the life and accomplishments of the 1991 Kyoto prize winner for earth and planetary sciences, see this article by Thomas Maugh.

I am certain I heard of chaos theory well before the movie Jurassic Park, but who can forget the pessimistic views the scientific character Doctor Ian Malcolm, who cited Lorenz's thories to predict the subsequent catastrophe of dinosauric proportions. This is a recurring theme of Jurassic Park author, Michael Crichton: Any complex system will inevitably break down due to the natural state of disorder, or entropy.

I fear that I shall always remain unclear on distinctions a fine as this – chaos vs entropy. Perhaps things may come into focus after I read this article on “Chaos, Complexity, and Entropy”-- a physics talk for non-physicists by Michel Baranger of the Center for Theoretical Physics, Laboratory for Nuclear Science and Department of Physics at Massachusetts Institute of Technology.

It seems to me that Lorenz in his chaos theory considered Earth’s meteorology as a system that often becomes so tightly wound that it comes right to the brink of breaking down -- so close that the tiniest disturbance, such as that caused by a benign Brazilian butterfly, can create a terrible upset. Being a chemical engineer, what comes to mind for me is a supersaturated solution of a salt that solidifies around the tiniest seed.

I only hope that I do not get twisted up in Earth's chaotic meteorology -- a very real possibility here at the northern end of the USA's tornado alley. Maybe a minnow in the Amazon is wiggling a fin at this very moment! I'd better bunker down in the basement...


  • At 5:34 AM, Anonymous Anonymous said…

    Chaos is what is behind the creation of residuals. All of the butterflies, minnows, and bloggers typing are causing noise in all of my experiments. So if everyone could just please hold completely still for the next 10 seconds ... ... Thank you, finally a run with no noise!

  • At 10:27 AM, Anonymous John King said…

    James R. Thompson of Rice University, in his book "Simulation, A Modeler's Approach", discusses Lorenz's work published in the Journal of Atmospheric Science in 1963.

    Lorentz was modeling weather with a system of three coupled non-linear differential equations. He found that very small changes in system initial conditions caused wildly divergent behavior of the system state as the system equations were solved further out in time. He proposed his findings as a reason for the poor results in making predictions of the weather.

    Thompson was skeptical and used a "discretized noisy version" of the original model to test Lorenz's conclusions. He found that the addition of a small amount of noise resulted in stable and repeatable results rather than chaotic behavior. In this case, chaos was a probably a mathematical artifact and the addition of noise had a stabilizing effect on system behavior.

    Thompson's conclusion? Physical processes such as weather are driven by large effects such as El Nino and jetstream currents. When realistically modeled they don't exhibit chaotic behavior, so the Butterfly effect probably isn't real.


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