# Year in Review: Progress made toward twin prime proof

## Surprising advance sparks flurry of work on mathematical conjecture

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Some pan for gold, some pan for prime numbers. Yitang “Tom” Zhang may have found both.

Zhang, a mathematician at the University of New Hampshire, stunned the mathematical world in May when he reported a major step toward solving one of the oldest outstanding problems in number theory, called the twin prime conjecture (*SN: 10/19/13, p. 38*).

For more than 100 years, mathematicians have known that prime numbers — such as 7 or 17, with no divisors except for themselves and 1 — get sparser and sparser as the numbers get larger. They are like flecks of gold in a stream that is gradually running out of gold.