When I talk about complexity to clients I mention that complex systems are impossible to predict in detail especially as your forcast extends into the future. I point out that there are so many connections among the objects affecting the system and many of the cause and effect relationships are non-linear (a small thing can have a big impact and vice versa). Every now and then someone will say, “but if you could work out all those connections you could predict the outcome.” And this is where I will tell them the chessboard story.

The legendary information scientist, Claude Shannon, calculated how many possible moves there are on a chessboard. It’s a finite system of 64 squares, 32 pieces, 6 movement patterns. The number is big and equates to the number of milliseconds the world has been in existence. And that’s for a simple system. Imagine the possibilities in a social system where the objects have free will.

But I think I’ve just read a better analogy (perhaps equally as impressive) and the topic is billiards. The calculations were done by Prof. Sir Michael Berry in 1978 in his paper Regular and Irregular Motion, in Nonlinear Mechanics and recounted in The Black Swan.

If you know a set of basic parameters concerning the ball at rest, can computer the resistance of the table (quite elementary), and can gauge the strength of the impact, then it is rather easy to predict what would happen at the first hit. The second impact becomes more complicated, but possible; and more precision is called for. The problem is that to correctly computer the ninth impact, you need to take account the gravitational pull of someone standing next to the table (modestly, Berry’s computations use a weight of less than 150 pounds). And to compute the fifty-sixth impact, every single elementary particle in the universe needs to be present in your assumptions! An electron at the edge of the universe, separated from us by 10 billion light-years, must figure in the calculations, since it exerts a meaningful effect on the outcome. (p. 178)

No wonder I can’t play billiards to save myself.

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