Butterfly Affection?

The Butterfly Effect. Unintended changes of future states based on small actions in the present, right? Well, one of the /. crowd informs us otherwise… I could never state it quite as clearly as him, so here’s an excerpt explaining the effect:

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"Perhaps you are neglecting the Butterfly Effect."

I am not. I have a degree in Mathematics in which I made a particular study of chaotic dynamical systems. I've written papers about the Butterfly effect; I've constructed physical models that demonstrate it. Let me tell you about the Butterfly Effect, so that you can refrain from bringing it up in discussions such as this in the future:

In a system which exhibits sensitive dependence on initial conditions (such as the weather), you cannot predict the details of long-term behavior (will there be a tornado in Iowa exactly 1 year from today) because tiny variations, well below what your measurement of the system could possibly account for (such as the breeze generated by the flapping of butterfly wings) will cause reality to drift further and further out of synch with your model until there is no resemblance on the detail level.

So the butterfly effect makes it impossible to ever predict what day it will rain months in advance, for example. But it does not prevent predictions about the aggregate, macroscopic behaviour of the system as a whole. In Meterological terms, long term weather prediction is impossible, but short-to-mid term climate prediction is easy.

Lets be ridiculously generous, and say this system takes a thousanth of a percent of the wind energy in the jet stream out. Is it reasonable to suppose this might cause significant changes in the world climate that will make a huge difference in its suitability for humans? No; it is not remotely reasonable. It's just not enough energy to make much difference.

Would it mean sometime in the future there will be a thunderstorm one day and not another? Absolutely. Whether you exhale the next breath you take slowly or forcefully means exactly the same thing; the minute difference in the velocity of a few thousand molecules of air your breathing pattern makes will eventually mean the difference in what day you get a thunderstorm.

The relevance of the Butterfly Effect in deciding whether to build this wind farm is the same as its relevance in deciding how forcefully to exhale your next breath. It means that the exact effect of either cannot be predicted, and that's it. It's not a reason to not do anything. (Well, except things like attempting long term prediction of weather detail.)

Hope that helps.