AlphaGo defeats Lee Sedol 4–1
DeepMind's Go program AlphaGo beat the top South Korean player Lee Sedol 4–1 in a five-game series, the DeepMind Challenge Match, held in Seoul from 9 to 15 March. AlphaGo took games one, two, three, and five, Lee Sedol took game four, and every game ended in resignation. Go's search space is vast enough that brute-force search of the kind that cracked chess does not work, and computers had been expected to need another decade to beat a top professional. That expectation collapsed at once. An estimated 200 million people watched, and the match impressed on the wider public that AI had reached into territory thought to require human intuition. Move 37 of game two, a shoulder hit outside human convention, startled professional players.