From the December 2004 issue

Catch a (gravity) wave

A home computer can run a screen saver that will help astrophysicsts detect gravitational radiation.
By | Published: December 27, 2004 | Last updated on May 18, 2023

Bruce Allen wants to take over your computer’s brain. But, really, it’s OK because he wants it only while it’s snoozing. You’ll hardly notice a thing.

Allen, a physicist at the University of Wisconsin-Milwaukee, is part of an international collaboration of scientists looking for gravity waves. These are ripples in the fabric of space-time predicted by Einstein’s theory of general relativity. Gravity waves should be emitted by the collision of massive objects, such as neutron stars or black holes, and by the shock waves produced when the core of a star going supernova collapses. Predictions also say gravity waves should radiate from spinning neutron stars that aren’t quite symmetrical. But despite decades of searching, scientists have not directly detected any gravitational radiation.

Four cutting-edge observatories – two in the United States, a third in Italy, and the fourth in Germany – have been built to find gravity waves. They work by ricocheting laser beams between mirrors as scientists look for minute distortions in the beams’ travel times. The Laser Interferometer Gravitational Wave Observatory (LIGO) has one installation in Livingston, Louisiana, and a second in Hanford, Washington, with two interferometers. VIRGO, the Italian instrument, is based at Cascina, near Pisa. The German instrument, GEO 600, is near Hanover and was built in collaboration with Great Britain.

The task these observatories face is difficult. A typical gravity wave is expected to distort the detector by less than a trillionth the width of a human hair. There’s no lack of signals in the data from these instruments, but separating spurious noise from the distortions produced by passing gravity waves is a challenge that requires loads of computer processing.

This is where Einstein@Home enters the picture. Modeled on the popular SETI@Home program, Allen’s Einstein@Home is looking for computer owners willing to donate bits of processor time to analyze the noisy data from gravity-wave observatories. Participants can install a Windows screen saver that periodically downloads raw data from the project’s web site and goes to work on it while the computer is otherwise idle.

Once you’ve set up an account and have the software running, you can set up a team and compete with others to gather the most computation credits, which are calculated from the speed and amount of data your computer processes. (Or you can join a pre-existing team, such as Astronomy‘s.) It takes about a week to accumulate computation credits, and only members who have received a credit are listed as “active.”

Einstein@Home is currently searching the most sensitive 840 hours of data from LIGO’s first science run at the detector’s design sensitivity. As Allen says, “Einstein@Home will offer real – and important – science at the grassroots level.”