Psst! Want to make a contribution to pioneering physics? Do you enjoy friendly competition? Want a jazzy screen saver? Then have I got the project for you!

Einstein@Home asks that you lend the idle CPU time of your home or work computer to physicists and astronomers now searching the sky for evidence of gravitational waves. The waves could result from stars exploding, black holes en-gulfing each other, or other acts of astronomical violence.

I got hooked on helping in late January when I showed up early in a California Institute of Technology laboratory of a physicist whom I was to interview for an article on gravitational waves. While waiting in the Pasadena lab, I noticed that all the computer screens displayed a gorgeous rotating celestial sphere [see illustration, above] that looked so three-dimensional I felt I could reach inside it. “Where’d you get the neat screen saver?” I asked when my interviewee appeared. “I want one.”

That’s exactly what physicists are hoping to hear.

 “We wanted something pretty that moves, to attract 100 000 people to the Einstein@Home project,” explains IEEE Member Bruce Allen, professor at the University of Wisconsin at Milwaukee, who conceived and designed the screen saver.

Einstein@Home is the flagship public education and outreach project of the American Physical Society. The APS is now celebrating the World Year of Physics 2005 to commemorate the centennial of Albert Einstein’s “miracle year” of 1905, when he wrote three key papers fundamental to modern physics, including his first on relativity. “We wanted something that teachers could use at school, to show the celestial sphere, and that kids would then want at home to run on their parents’ computers,” says APS spokesman James Riordon.

REAL PHYSICS  But Einstein@Home is far more than a public relations project to raise awareness of physics. It’s real physics itself. Download the screen saver, and you’re also downloading a program that will calculate whether any direct evidence of gravitational waves can be discerned in the raw data obtained from the Laser Interferometer Gravitational-Wave Observatory (LIGO) project. The observatory’s telescopes (one in Hanford, Wash., and the other in Livingston, La.) will begin full-time operation late this year.

Gravitational waves are predicted by Einstein’s general theory of relativity. Einstein said that what we feel as a gravitational field actually results from the fact that huge masses (such as the earth and stars) curve the very geometry of space and time. The more massive an object is, the more it bends space and time—something other bodies sense as a greater gravitational field. And if the object’s gravitational field changes—say, when a star explodes or one black hole engulfs another—then that change literally propagates as a ripple, or wave, through space and time, rather like ripples radiating outward in a pond from a disturbance in the water. These ripples in the geometry of space-time are the gravitational waves LIGO is trying to measure.

But you don’t need to know about exotic physics to understand or appreciate Einstein@Home. The basic principle is “many hands make light work”—and at lower cost.

Looking for evidence of gravitational waves is similar to the challenge of searching for signals from extraterrestrial intelligence: physicists have no idea what kind of signal to expect, or at what frequencies, or from where in the sky it might come. So they are faced with examining all points in the sky at all frequencies for as long as possible. That makes for a monumental task of truly daunting proportions, requiring millions of hours of computing.

But it also is a problem of a form that mathematicians call “trivially parallel”—meaning that each calculation at a particular frequency or point in the sky is completely independent from any other calculation at another frequency or point in the sky. Thus, individual calculations can be readily parceled out to independent machines, as has been done by enlisting 3 million helpers in the University of California at Berkeley’s SETI@Home project, searching for extraterrestrial intelligence since 1999. (Sorry, no extraterrestrial signals have yet been found.)

The software for Einstein@Home is called BOINC, a whimsical acronym for Berkeley Open Infrastructure for Network Computing. It’s the brainchild of IEEE Member David Anderson, project director at the Space Sciences Laboratory at Cal-Berkeley. Effectively, BOINC unites PC, Macintosh, and Unix machines around the world into one massive super-computer for Einstein@Home. BOINC is also being used by SETI@Home and about half a dozen other massively parallel computing projects.

“The long-term goal of BOINC is to get everybody in the world directly involved in volunteer computing for science,” Anderson says. The potential numbers are impressive. According to Anderson, there are 200 million privately owned personal computers connected to the Internet. Worldwide, that’s a phenomenal amount of computing power that is often idle and could be harnessed for science.

Even for Einstein@Home, the newest BOINC project, the numbers are already big. Since going public in mid-February, Einstein@Home now has some 45 000 participants, whose collective computers have more than 20 times the power of LIGO’s own machines.

Not only are the volunteer computers handling 20 times as much data as LIGO can for itself, but BOINC also is saving LIGO big bucks. “The average PC draws 100 to 150 watts, so 45 000 computers are burning about 6 megawatts,” Allen estimates. “At Wisconsin electric power rates, that’s saving the LIGO project US $7000 a day. Plus people are keeping an eye on their machines, saving LIGO the cost of maintenance.”

THE PAYOFF What’s in it for you? Aside from the hypnotically peaceful screen saver, it’s just plain fun watching your credits mount. Credits are an arcane dimensionless indication of how much of a contribution your computer has made to the project; every time your computer dials out to upload its results and download new raw data from Einstein@Home, the number jumps (my credits now top 50 000).

“Credits are like Monopoly money,” Allen explains. “People get very competitive and are excited to see how they stand compared with other participants.” Encouraging whatever psychology works to keep people and their computers involved, the Einstein@Home site regularly updates statistics on individual computers and even teams of participants, invites participants to create their own Web pages, and explains the individual work your own computer is calculating.

If one day LIGO detects gravitational waves, what do Einstein@Home participants get—a share of a Nobel Prize? A bottle of wine? An acknowledgment in a scientific paper? “In the end, you get a number: your credits, which give you a feel for your level of participation in the project,” Allen says, “and the knowledge in your heart that you directly contributed to pioneering physics.”

FOR MORE INFORMATION about the Einstein@Home project, visit http://www.einsteinathome.org. Details about the World Year of Physics 2005 are at http://www.physics2005.org. More about BOINC is available at http://boinc.berkeley.edu.