Catch a gravity wave with Einstein@Home
February 19, 2005
When no other tasks are in progress, Einstein@Home displays a celestial sphere showing the brightest stars, a plot of pulsars, markers for the threee gravity-wave observatories responsible for the data it processes, and a cursor illustrating the current sky position being analyzed.
Photo by Einstein@Home
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February 19, 2005
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Einstein@Home — How scientists look for gravity waves — How the program works — Einstein@Home fast facts — Join Astronomy magazine's Einstein@Home team — Einstein@Home contact information — Astronomy contact for Einstein@Home
Armchair astrophysicists rejoice: Now, you can help scientists find gravity waves — ripples in the fabric of space-time caused by spinning neutron stars.
All you need is a computer, a fast connection to the Internet, and the Einstein@Home screensaver. Following months of testing with some 9,000 users, the program is now available to everyone.
Bruce Allen, a professor of physics at the University of Wisconsin, Milwaukee (UWM), and leader of the Einstein@Home project, announced he was "throwing open the doors" to the public at the annual meeting of the American Association for the Advancement of Science in Washington, D.C. The project is the result of collaboration between UWM, the California Institute of Technology, and the Albert Einstein Institute in Germany.
"Most of what exists in space is not visible," says Allen. Finding gravitational waves "gives us another mechanism for learning about black holes and other space events firsthand."
Einstein's general theory of relativity predicts that objects such as spinning superdense neutron stars, collapsing and exploding stars, and black holes emit gravity waves, which move unseen through the universe, subtly distorting the world around us.
Although these waves have gone undetected so far, astronomers have seen their effects. For example, when a radio-emitting neutron star known as a pulsar is paired up with another star, the pulsar gradually tracks an ever-smaller orbit. The orbital energy it loses matches the energy relativity predicts the pulsar will emit as gravity waves.
Just as light carries information about a star's surface to Earth, gravitational ripples in space-time will bring us invaluable clues about the interiors of stars and the nature of gravity itself. Three facilities — two in the United States and one in Germany — are actively searching for these waves and have collected massive amounts of data. Einstein@Home is designed to sift through hundreds of hours of these observations for signs of a passing gravity wave.
The project uses a technique called "distributed computing," which means it relies on computer time donated by private computer users to search through the data, an approach that is gaining popularity in many scientific fields. In fact, Einstein@Home was constructed with input from the architects of SETI@Home, a popular distributed computing project that searches radio-telescope data for signals from extraterrestrial civilizations.
Astronomy associate editor, Francis Reddy, looks forward to the opportunity this project offers. "We're really excited about this," Reddy says. "The technology gives anyone with a computer an opportunity to make a real scientific contribution. A discovery with Einstein@Home would not only be the first detection of gravity waves, but the first discovery using distributing computing."
How scientists look for gravity waves
Three cutting-edge observatories have been built to find gravity waves. All work by ricocheting laser beams between mirrors as scientists look for minute distortions in the beams' travel time. The Laser Interferometer Gravitational Wave Observatory (LIGO) has one installation in Livingston, Louisiana, and a twin in Hanford, Washington. The German instrument, GEO600, is near Hanover, Germany, and was built in collaboration with the United Kingdom.
These observatories face a difficult task. A typical gravity wave is expected to distort a laser's path 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 requires loads of computer processing.
"Our current instruments will be able to see the merger of two neutron stars to tens of millions of light-years," says Allen. But because the system is less sensitive to impulsive events — like exploding stars — he notes, "We will probably only be able to see supernovae within our own galaxy, although this depends upon the detailed physics of what happens during a supernova, which is not fully understood."
Scientists are conducting other searches for signals from these exotic sources, but Einstein@Home focuses on objects producing continuous waves, such as fast-spinning pulsars. This, says Allen, is the most computationally intensive task.
How the program works
Einstein@Home downloads data from the LIGO Scientific Collaboration through an Internet connection. Because these "work units" are rather large, Allen suggests only those people with a broadband Internet connection — cable modem or DSL — join the project. The program processes data as a background task according to preferences you set. When Einstein@Home completes each work unit, it reports the results back and retrieves another block of data.
When the computer is performing no other tasks, Einstein@Home displays a celestial sphere showing the brightest stars, constellation lines, a plot of known pulsars and supernova remnants, and symbols for the three gravity-wave detectors. A cursor slowly moves across the globe, charting the location of data currently being processed.
Einstein@Home tracks the data processed by different computers, and users can join forces with others to collaborate as teams.
Einstein@Home is available for Windows, Mac (OS X), Linux, and Sun Sparc computer platforms.
Einstein@Home fast facts
Einstein@Home looks for pulsars — spinning neutron stars — over the entire sky using the best 600 hours of data from LIGO's third science run (October 2003 - January 2004).The United Nations has dubbed 2005 the International Year of Physics in celebration of the centennial of Einstein's "miracle year" — when he published three groundbreaking scientific advances including relativity and an explanation for the photoelectric effect.In 1993, the Nobel Prize in Physics went to Russell Hulse and Joseph Taylor of Princeton University for their 1974 discovery of a pulsar, designated PSR1913+16, in a binary system — in orbit with another star around a common center of mass. They showed the pulsar's orbit was shrinking by the amount expected by relativity's prediction of gravity waves.In 1921, Einstein was awarded the Nobel Prize for "for his services to Theoretical Physics, and especially for his discovery of the law of the photoelectric effect."Visit World Year of Physics 2005 for more exciting, international projects and events.
Join Astronomy magazine's Einstein@Home team
Einstein@Home contact information:
Bruce Allen (Saturday evening):
On Monday, February 21, he can be reached at 414.229.6439
Astronomy contact for Einstein@Home:
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