Volunteers Help Find a New Prime

Climbing fast. Mersenne primes grow so quickly that the 39th in the series is 4 million digits long.

Prime numbers are the basic building blocks of the mathematical world. Every natural number other than one is either prime or the product of primes multiplied together. Now scientists are about to add a new number to their list of a rare breed of primes, known as Mersenne primes.

The discovery is the 39th known Mersenne prime, a set of numbers that are of the form 2p - 1, where p must also be a prime number. Because of that exponential 2p, Mersenne primes rapidly get very, very large. So when a project called the Great Internet Mersenne Prime Search (GIMPS) found the new number, nobody was surprised that it topped the scale. The previous record holder, 26,972,593 - 1, is more than 2 million digits long and was found by GIMPS two and a half years ago.

The new prime was discovered thanks to a technique also being used to search for extraterrestrial life and new AIDS drugs. In an approach called distributed computing, volunteers run programs on their computers when the machines would otherwise be idle. Thousands have downloaded a program that runs a Mersenne-prime-testing algorithm, called the Lucas-Lehmer test, and in mid-November, one volunteer reported a prime sighting. Tim Cusak of Entropia, a San Diego-based distributed computing company that provides the network backbone to the search, says he expects the new prime to be confirmed this week by a second test on a supercomputer.

Meanwhile, the search continues. Finding ever-greater Mersenne primes isn't terribly important to number theorists, but GIMPS soldiers on, hoping to set ever-increasing world records. Perhaps, for the participants, the search evokes something primal.

Related sites

The Great Internet Mersenne Prime Search
Biographical site of Marin Mersenne

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