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At its core, the game of Go, which originated in China more than 2,500 years ago, is an abstract war simulation. Players start with a completely blank board and place black and white stones, one at a time, to surround territory. Once placed, stones do not move, and they’re removed only if they’re “killed”—that is, surrounded completely by the opponent’s stones. And so the game goes—black stone, white stone, black stone, white stone—until the board is covered in an intricate tapestry of black and white.
The rules of Go are simple and take only a few minutes to learn, but the possibilities are seemingly endless. The number of potential legal board positions is:
That number—which is greater than the number of atoms in the universe—was only determined in early 2016. Because there are so many directions any given game can move in, Go is a notoriously difficult game for computers to play. It has often been called the “Holy Grail” of artificial intelligence.
In February 2016, DeepMind researchers published a paper in Nature that announced that they’d done something remarkable: Not only could their AI beat every other Go-playing program in the world, but it had beaten a professional named Fan Hui, the current European champion. AlphaGo didn’t just beat Fan Hui—it beat him soundly in every match of a five-game series.
The news rippled through the Go world. It was widely believed that an AI strong enough to beat a professional player was still at least a decade away, and that milestone had been quietly crushed. The next logical step was to discover what AlphaGo’s upper limit might be, and Lee was the logical choice for humanity’s champion.
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It’s curious that when someone is really good at something, we call them a “machine.” Lee Sedol is a Go-playing machine, enlisted to beat, well, a Go-playing machine.
Lee is not a machine, of course. He is a particularly young-looking 33-year-old. He is a man who gets up and eats breakfast, takes naps, feels embarrassed, gets nervous. Within the Go world, however, nobody is scarier than Lee, who plays with an unnerving confidence. He creates situations that should end in disaster and then—effortlessly to the observer—turns them on their heads, like a magic trick, steamrolling his opponents.
In the weeks leading up to Game 1, the DeepMind team expressed humble optimism about AlphaGo’s chances of winning. Lee is more brazen; at a press conference with Demis Hassabis, DeepMind’s founder, he claimed that for him, the challenge isn’t whether he’ll beat AlphaGo, but whether he’ll beat it 5-0 or 4-1.