Initially hailed as a solution to the biggest question in computer science, the latest attempt to prove P ≠NP – otherwise known as the "P vs NP" problem – seems to be running into trouble. Two prominent computer scientists have pointed out potentially "fatal flaws" in the draft proof by Vinay Deolalikar of Hewlett-Packard Labs in Palo Alto, California. Since the 100-page proof exploded onto the internet a week ago, mathematicians and computer scientists have been racing to make sense of it. The problem concerns the speed at which a computer can accomplish a task such as factorising a...