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     It’s that point when a smooth river turns into a tumultuous swirl of white water, the tornado that unpredictably changes course on a dime or the wild interactions of three planets under one another’s gravitational pull.

It’s chaos.

Although most people instinctively know chaos when they see it, there hasn’t been one, single, universally agreed-upon mathematical definition of the term. Now, scientists have tried to come up with a mathematical way to describe such chaotic systems.

The new definition, which was described in a paper published in July in the journal Chaos, could help identify seemingly smooth situations where the potential for chaos lurks, said study co-author Brian Hunt, a mathematician at the University of Maryland, College Park.

Chaos theory

Mathematician Henri Poincaré first encountered the wild state while trying to describe the behavior of three celestial bodies under one other’s gravitational influence. Their movements proved difficult to predict beyond a few steps, and he termed this kind of erratic motion “chaos.” Unlike truly random behavior, however, those systems were still “deterministic,” meaning that if one knew all the past laws and forces acting on the systems, one could perfectly predict where they would be in the future. (By contrast, at the subatomic scale, particles are fundamentally uncertain, meaning there’s no way to perfectly predict what a given teensy particle will do.)

But scientists didn’t really notice the chaos swirling in the universe until the 1960s, when computers had become powerful enough to crunch numbers and solve equations that couldn’t be…

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