Space chaos: The three-body problem explained

Kepler-16b, the first directly detected circumbinary planet, which is a planet that orbits two stars.

From rocket launches to alien worlds, a surprising challenge pops up: the three-body problem. But what exactly is this cosmic brain teaser?

Imagine a system with three celestial bodies, all tugging on each other with gravity. Sounds simple, right? Wrong. This problem has been a thorn in physicists' sides since Isaac Newton's time, according to Billy Quarles, a planetary scientist at Valdosta State University.

Two bodies, like a planet and its star, are easy. They typically orbit each other in a predictable loop. But add a third body, like another star, and things get messy. This third body disrupts the harmony, yanking the other two out of their neat paths.

The outcome hinges on the starting conditions – the positions, speeds, and masses of the bodies. Even a tiny tweak can drastically alter their future. "Think of balancing on a ridge," says Shane Ross, a mathematician at Virginia Tech. "A slight shift could send you tumbling one way or the other. Tiny differences lead to wildly different destinies."

Unfortunately, there's no simple equation to solve the three-body problemthe three-body problem. However, some special cases do have solutions. Three bodies of equal mass, for instance, can chase each other in a figure-eight pattern under specific conditions. But these tidy solutions are rare in the real universe.

Sometimes, simplifying the system helps. Take Tatooine, Luke Skywalker's home planet from Star Wars, with its twin suns. If the planet orbits both suns from a great distance, we can treat it as one larger object, simplifying the problem to a more manageable two-body system. Scientists have actually discovered over a dozen such Tatooine-like planets!

But more often than not, the chaos reigns. The gravitational tug-of-war can lead to collisions or slingshot one body out of the system entirely, creating "rogue planets" with no stellar home. In fact, three-body chaos might be so common that rogue planets could outnumber stars in our galaxy by a factor of 20!

For complex situations, computers come to the rescue. They can simulate the movements of celestial bodies, allowing us to predict rocket trajectories or the fate of planets in multi-star systems.

This brings us to Netflix's "3 Body Problem," where a planet endures a chaotic dance around three suns in Alpha Centauri, our closest neighboring star system.  (Spoiler alert!) With such constant upheaval, could life possibly exist on this world? "Probably not," says Ross. This is where the show ventures into the exciting realm of science fiction.


The Three-Body Problem

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A breakthrough book . . . a unique blend of scientific and philosophical speculation.” ―George R. R. Martin, on The Three Body Problem