Published online 1 February 2005 | Nature | doi:10.1038/news050131-7


Home computers search for gravity waves

Physicists hope to exploit the downtime of a million machines.

The Einstein@home screensaver will scan the sky for bell-like vibrations in space-time.The Einstein@home screensaver will scan the sky for bell-like vibrations in space-time.© B. Allen, Einstein@home

Scientists searching for waves of gravitational energy that stretch space and time will soon be seeking the public's help in analysing their data.

Researchers at the Laser Interferometer Gravitational Wave Observatory (LIGO) hope to enlist up to a million personal computers in their search for sources of the waves, which have long been predicted but never seen.

Their distributed-computing scheme, set to launch this month, aims to be one of the largest projects of its kind ever created. The software is already in beta testing.

“This kind of search is nowhere near possible with our LIGO computers.”

Barry Barrish
California Institute of Technology, Pasadena

Albert Einstein's general theory of relativity lays out the idea that gravity distorts space and time. As a test of his theory, Einstein predicted that waves of gravity would ripple through the cosmos. Some claim such waves have been spotted indirectly, from observations of how paired stars influence each other's orbits, but nobody has seen them firsthand.

Since 2000, researchers at LIGO have scanned the sky for tiny shifts of space that would prove Einstein's theory. The project is being built by the California Institute of Technology and the Massachusetts Institute of Technology on two sites, one in Livingston, Louisiana and the other in Hanford, Washington. It uses a system of lasers and mirrors that can detect a shift in space as small as the width of an atom.

Bell ringers

LIGO's best hope for detecting gravity waves is to spot a cosmic source that sends out regular ripples of gravitational energy. A source such as a spinning star made of neutrons would set the detectors ringing like a bell.

The problem is that the detectors pick up an enormous number of unwanted vibrations. "It's a needle in a haystack problem: 99.99% of the data is noise," says Bruce Allen, a physicist at the University of Wisconsin at Milwaukee.

"This kind of search is not anywhere near possible with our LIGO computing facilities," adds Barry Barrish, head of the collaboration and a physicist at the California Institute of Technology, Pasadena. The data must be analysed at many frequencies, increasing the computer power needed.

So the group is enlisting the public's help. Starting in February, anyone can download a program. that will automatically analyse a small chunk of the group's data on his or her personal computer.

The project, known as Einstein@home, will use the computer's idle time to search particular frequencies for a 'ringing' gravity wave source. While it's at work, the programme also displays a screensaver charting the location of the search in the night sky. "It's really a cool kind of project," Allen says.


Einstein@home joins a growing number of distributed-computing projects. The original, SETI@home, launched in 1999 to search for signals from extraterrestrials, has attracted more than 5 million users. More recent attempts to model everything from climate change to protein folding have enlisted hundreds of thousands of home computers.

Einstein@home will be among the most ambitious of such projects, Allen says. LIGO is generating data sets so large, and looking for a signal so small, that it will take around a million active users to make a dent. But, he adds, the more the merrier: the data set is so massive that "even all the computers on the planet wouldn't be enough". 

California Institute of Technology, Pasadena