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'Butterfly Effect' Theorist Lorenz Dies

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'Butterfly Effect' Theorist Lorenz Dies


'Butterfly Effect' Theorist Lorenz Dies

'Butterfly Effect' Theorist Lorenz Dies

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  • <iframe src="" width="100%" height="290" frameborder="0" scrolling="no" title="NPR embedded audio player">
  • Transcript

Meteorologist Edward Lorenz has died. He laid the foundations for the field of scientific study called chaos theory. He famously suggested that a butterfly flapping its wings in Brazil could ultimately produce a tornado in Texas.


From NPR News, this is ALL THINGS CONSIDERED. I'm Michele Norris.

One of the pioneers of chaos theory has died. Edward Lorenz was famous for the butterfly effect - that's the idea that an insect flapping it's wings in one place could lead to a tornado, a continent away.

NPR's David Kestenbaum reports that Lorenz's work helped challenge the comfortable notion that the world is an orderly and predictable place.

DAVID KESTENBAUM: Edward Lorenz was a meteorologist, and back in the 1960s, he was trying to understand how the atmosphere worked using one of the first computers - you know, those magic calculating machines that don't make mistakes. So he was surprised when he ran a simulation once, ran it again, and got a different answer.

Kerry Emanuel is one of Lorenz's former students and heard him tell this story in class.

KERRY EMANUEL: He naturally assumed something was wrong with the machine and called in the technicians, and they came and said, no, this machine seems to be working fine.

KESTENBAUM: Lorenz realized that the second time he ran the program, he had started it off slightly differently, but only very slightly. Instead of feeding it, say, 0.5068, he rounded that off to 0.507.

EMANUEL: Which, under most calculations, just - you just can't notice, you know, it's a one-tenth of 1 percent rounding error. But he finally realized that it was that tiny little error that had - in the subsequent calculation - amplified to completely change the results.

KESTENBAUM: Emanuel says, as a student, this story was a revelation. He had been raised to think of the world as basically predictable. That weather forecast would get more and more precise. This finding meant there were limits. You're just not going to be able to predict the weather two weeks in advance.

EMANUEL: And I even remember in the '70s arguing with my fellow students, and even in one or two cases with Physics professors at MIT. And they really fought it back then, I didn't believe it, they didn't sound reasonable or right.

KESTENBAUM: You can trace the roots of chaos theory to the last century. But Lorenz had found a concrete example that was hard to ignore. He wrote a paper titled, "Does the Flap of a Butterfly's Wing in Brazil set off a Tornado in Texas?"

Well, can it? We called another one of Lorenz's students, Isaac Held. A scientist at the National Oceanic And Atmospheric Administration.

ISAAC HELD: But the butterfly has to be big enough, I think.


HELD: I would say meters.

KESTENBAUM: He says the butterfly effect does show up in the huge super computer models now used to forecast the weather. All you have to do is tweak the temperature at one spot on Earth by a fraction of a degree.

HELD: Then a month later, the weather will be very different throughout the whole world.

KESTENBAUM: Scientists have used chaos theory to try to understand the stock market and animal populations. Nonscientists thought it was cool, too.

In the movie "Jurassic Park," chaos theory is the reason for why the dinosaurs take over, and a Japanese composer wrote a symphony inspired by Lorenz's work. Kerry Emanuel who worked with him in MIT found the idea of limited predictability liberating. Without it, he says, the universe just looks like a big machine with little room for free will.

EMANUEL: You're just a cog in the clock; it's a very depressing notion.

KESTENBAUM: Emanuel went on long hikes with Lorenz, often scrambling to keep up. He says Lorenz didn't talk much about the philosophical consequences of his work. But he did write, in one of his books, that we should believe in free will.

EMANUEL: He said, if I'm right, I'm right. If I'm wrong, I never chose in the first place.


EMANUEL: That's a very clever, you know, typical Lorenzian logical construction.

KESTENBAUM: Edward Lorenz was 90 years old.

David Kestenbaum, NPR News.

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