Mathematician who after 1,200 hours of computer calculations was able to solve an age-old problem
Kenneth Appel solved a long-standing mathematical conundrum, but he did so in a way which drew fierce disapproval from his peers — he used a computer.
The question which Appel set himself to answer sounds simple enough: how many colours are needed to colour a map (assuming the regions consist of single entities), so that regions sharing a common border are a different colour?
The question, first raised by the mathematician Francis Guthrie after colouring in the counties on a map of England, was put to the London Mathematical Society in 1878. The answer was generally thought to be four. But