Winning at cards requires both luck and skill. On his fourth day of play at the 2010 World Series of Poker in Las Vegas, Petter Northug’s luck ran out–but not before he had survived long enough to win more than $20,000. With fewer than 700 players remaining from an original pool of more than 7,000, Northug was eliminated, on a hand that he had less than a 20 percent chance of losing. Late in the...