For a while in the mid-2000s, a refrigerator-sized box in Abu Dhabi was considered the greatest chess player in the world. Its name was Hydra, and it was a small super-computer—a cabinet full of industrial-grade processors and specially designed chips, strung together with fiber-optic cables and jacked into the internet.At a time when chess was still the main gladiatorial arena for competition between humans and AI, Hydra and its exploits were briefly the stuff of legend. The New Yorker publishe...