Henry Laufer was teaching math at Stony Brook University on Long Island in the late 1980s when he got a call from Jim Simons. A former colleague, Simons had left academia to start Renaissance Technologies a mile down the road, and his hedge fund was struggling. Would Laufer help him find a better way to predict commodity prices? Three decades later Laufer is a billionaire four times over, and Simons is even richer. Their Medallion Fund, based on models that find signals hidden in the noise of markets, has become probably the world’s most successful money machine. Powered by millions of...