Einstein@Home: a mega-computer for gravitational waves

Bernard Schutz, Albert Einstein Institute schutz-at-aei.mpg.de
With the help of the American Physical Society, the gravitational wave community is hoping to enlist home computers all over the world in the search for gravitational waves. The initiative, named Einstein@Home, is one of APS's World Year of Physics 2005 projects. After the official release of the software in the first quarter of 2005, anyone will be able to visit the APS website http://www.physics2005.org/ and download a screensaver that will enable any idle computer to become a part of the global gravitational wave data analysis network.

Einstein@Home is being developed by a team of scientists and programmers from the LIGO Scientific Collaboration (LSC), led by Bruce Allen of the University of Wisconsin Milwaukee (UWM). The idea for the project arose in discussions in 2003 between James Riordon of the APS and members of the gravitational physics community. Riordon wanted to use the ``Einstein Year" to provide some practical help to physics, not just public relations, and he thought that a screensaver could be the ideal vehicle. The GW community certainly needs practical help: the sensitivity of the search for gravitational wave pulsars will be limited by the available computer power, and even the several teraflops of cluster computers available within the LSC can make only a small dent in the problem.

Einstein@Home could make a real breakthrough in the available computer power. Even in the preliminary testing phase of the software, enough users signed up for it that it could deliver more CPU cycles than any other LSC computer. The screensaver is designed to give the computer's owner a sense of participating in an important project. It displays a rotating globe of the constellations, on which are shown all the known pulsars, the current sidereal locations of the LIGO and GEO600 detectors (whose data will be analyzed), and the place on the sky where the computer is currently doing its search for pulsars. Each computer gets a small amount of data from an Einstein@Home server, does the analysis, and returns the result. Even if the computer is temporarily disconnected from the internet (say, a laptop PC), the analysis will be completed and the software will wait for the next opportunity to update itself. Users get feedback about how much they have contributed to the effort, and they can even join teams that compete to provide more and more cycles!

It is no coincidence that the project's name resembles that of SETI@Home. The SETI project (Search for Extraterrestrial Intelligence) originated the screensaver-for-science idea, and it has so far managed to engage hundreds of thousands of computers in the analysis of short stretches of radio telescope data for possible non-random signals. The SETI software inspired an open-source product, called BOINC, written by SETI@Home developer David Anderson. Einstein@Home is based on the BOINC tools. In fact, the Einstein@Home team has made significant contributions to BOINC itself. Scientists from LIGO, UWM, and the Albert Einstein Institute in Germany have participated in the project.

The Einstein@Home software will run on PCs, Macs, and Linux machines. Bruce Allen is hoping not only that members of the general public will catch GW fever and sign on, but also that university groups will install the screensaver in their computer instruction labs and on their departmental workstations. Even typical computers sold in today's mass market deliver performance within factors of 5 or better of the chips used in many high-performance clusters, so most university physics departments can deliver a good fraction of the dedicated computer power at any of the LSC computer installations. If Einstein@Home can achieve one hundred thousand users (which certainly seems possible), it might well turn out that the first gravitational wave source to be discovered will be a pulsar found by someone's home PC!

Jorge Pullin 2005-03-10