'Random' primes pair up on the sly

摘要

Prime numbers are pickier about how they sit than we thought. Mathematicians have been stunned to find that these numbers aren't quite as haphazard as they seem. Understanding primes -numbers divisible only by themselves and 1 - is key to deciphering the fundamentals of arithmetic. Mathematicians don't have a way to predict which numbers are prime, so tend to treat them as if they occur randomly. But now Kannan Soundararajan and Robert Lemke Oliver of Stanford University in California have discovered that isn't quite right. "It was very weird," says Soundararajan. "It's like some painting you are very familiar with, and then suddenly you realise there is a figure in the painting you've never seen before."