Many people believe that there are other intelligent life forms in our universe. Scientists have considered the different ways that these extraterrestrials could contact us, and now believe that the easiest way for them to try to contact us would be via electronic signals. Most scientists also agree that radio waves would be the simplest, most efficient way for extraterrestrials to contact us. This is because some radio wave frequencies do not require a lot of power, and, if energy was concentrated in one frequency, it could easily be distinguished from other frequencies or "background noise," that humans toss into space with television and radio broadcasts. However, there was no way to know for certain if these theories were true; using traditional methods to examine the sky for waves and processing the data would be extremely difficult. Even using computers would not work, as supercomputers would be fast enough to process data yet too expensive, and smaller computers would be cheap enough to buy yet too slow. (Hipschman) These problems remained unsolved until SETI@home was created.

The Search for Extraterrestrial Intelligence program, also known as SETI, was developed in 1984 by the SETI Institute of University of California Berkeley to conduct scientific research about the universe and possible life forms. Most of their research was done using traditional telescope methods. SETI@home was conceived 11 years later when the SETI team discovered that, for a search the magnitude of the universe, they'd need a lot of computing power. The UC Berkeley SETI team considered the Internet, and all the computers that sit idle "with toasters flying across their screens." (Hipschman) The idea behind SETI@home was to have Internet users help the team process telescope data in a much quicker, less expensive way.

The creators of SETI@home, David Gedye and Craig Kasnoff, formed a project team and offered this idea to the 5th International Conference in Bioastronomy in July 1996. There it was widely supported, and the team decided to forge ahead. For the next few years the SETI team devoted their time to project funding and creating the client and server software, with project director David Anderson in charge. Finally, on May 17, 1999, the SETI@home website officially opened to the public. User response was huge, with over 100,000 users showing interest before the site was open. There are currently over two million CPUs running SETI@home software. According to Dr. Jill Tarter, a SETI scientist, the program was so popular that SETI@home's hardware had to "be upgraded the moment it was turned on!" ("Jill Tarter...")

The Arecibo telescope in Puerto Rico gathers data consisting of radio signals almost every day. The data it receives in one day is 35 gigabytes ‹ too large to be sent over the Internet. Instead, the data is shipped as regular mail to UC Berkeley, where it is divided up and sent out to everyone with SETI@home client software. Across the internet, people receive "work-units" ‹ .25 megabyte chunks of data.

A computer will process the data in its idle time, checking the radio frequencies. Instead of checking a broadband signal, which would be spread over a large number of frequencies, the scientists focus on specific frequencies. The scientists are especially interested in the frequencies with a lot of strength within a narrow bandwidth ‹ which could suggest an extraterrestrial message.

It should take most computers between 10 and 50 hours to complete one work unit. In that time, the computer will have done more than 175 billion calculations on the 107-second piece of data. (Hipschman) Then the work-unit will be sent back to SETI's servers and the computer will receive a new work-unit.

SETI@home is the most widely-known distributed computing project, with more than two million users searching for extraterrestrial life. All of these CPUs have done more than 300,000 years of work so far, averaging almost a millennium a day. Although there have been a few false alarms ‹ it turned out that the Arecibo telescope had been dysfunctional ‹ nothing has yet been found. The SETI researchers realize that the odds of actually finding life is slim ‹they believe there is perhaps a 1% chance ‹ but the users don't seem to mind. In fact, people continue to sign up; every day, at least a few hundred users register, making this not only the largest distributed computing project ever, but also, in essence, the world's largest supercomputer.

The SETI@home search is a parallel distributed computing project. All data is independent of one another because each work-unit represents some frequencies from a small section of sky and, to process the data, the computer doesn't need information about the other work-units. Thus, each user gets a different piece of the sky for their computer to analyze. SETI@home has three servers, dubbed Sagan, Asimov, and Cyclops. Sagan sends out the work units while Cyclops and Asimov have database servers that keep track of interesting data. (Rheingold 178) Sagan stores all work unit information received from Arecibo, which is useful if a specific work-unit needs to be spliced and sent out again. This would happen if a computer stops using SETI and never sends in the completed work-unit; SETI can easily send that unfinished work-unit to another user.

The SETI@home project also has some unique differences from other distributed computing projects. It uses a closed-source client in order to protect the data since it would be detrimental to the project if data was altered. The SETI project is also finite; there is only so much sky that can be seen from the Arecibo telescope. Other projects, such as the PiHex project and the Great Mersenne Prime Search (GIMPS) are infinite, as Pi could ‹ with enough computer power ‹ be calculated to a trillion places. The GIMPS project could also continue for quite some time since there is an infinite number of primes.

SETI@home is slated to run for only two years. By then, the entire amount of sky that can be seen from the Arecibo telescope will have been analyzed three times. The SETI scientists hope that, at the project's completion, there will be new technology and new techniques to analyze radio signals and search for extraterrestrial life. There are also plans to create a SETI@home II, which might use a telescope in Australia to expand the amount of data that could be analyzed. This project, too, would utilize the computing power the Internet has to offer by taking advantage of the concept of distributed computing.