In what is expected to be the most ambitious attempt ever to harness the combined computing power of hundreds of thousands of personal computers; a group is preparing to distribute a special alien-hunting screen saver to anyone with access to the internet. The project is called SETI@home, the UNIX software is available now, and the general software is due for release later this month. This is the perfect opportunity for anyone with an interest in the search for extraterrestrial intelligence to make an active contribution to the search. 

The History of SETI 
Although interest in the question of extraterrestrial life is as old and probably older than our own historical civilisations, the Search for Extra Terrestrial Intelligence (SETI) didn’t really begin until 1959, when two Cornell physicists published an article in Nature. In this article they proposed the potential for using microwave radio waves to communicate with extraterrestrial civilisations across interstellar distances. The following year, Frank Drake, a young astronomer who independently reached the same conclusion, conducted the first microwave radio search for signals from other solar systems. Frank Drake’s search (which was named Project Ozma, after the queen from the imaginary land of Oz) only monitored a single radio frequency over two months, but its pioneering steps led the way for numerous other searches for extraterrestrial civilisations. 

In the early 1970's, NASA conducted a study named Project Cyclops, which began to consider the technology required for an effective search. The Cyclops report provided a vital analysis of the science and technology upon which subsequent searches were based. Throughout the 1970’s the perception grew that SETI had a reasonable possibility of receiving an extraterrestrial signal, and a number of small searches were conducted by radio astronomers using existing radio telescopes. 

The High Resolution Microwave Survey 
By the late 70's, there were SETI programs established at NASA's Ames Research Centre and at the Jet Propulsion Laboratory in Pasadena. These two groups decided on a combined strategy for a massive SETI project. A decade of study and preliminary design went into the project, and in 1988, NASA Headquarters formally adopted and funded the program. They called the project the High Resolution Microwave Survey (HRMS) and it was planned for 10 years of observation. The observations began in 1992, but within a year, Congress terminated funding due to budget pressures (this is an example of the short-sighted, money-orientated nature of the American Congress). 

There is a popular rumour that the reason for the HRMS being cancelled was part of an elaborate conspiracy to stop the public from knowing about the existence of extraterrestrial intelligence. However, if it was the Congress' intention to suppress the search, they were unsuccessful… 

Phoenix is born 
Project Phoenix took over the HRMS with private funding. Phoenix began observations in early 1995 using the Parkes 210 foot radio telescope in New South Wales, Australia (the largest radio telescope in the Southern Hemisphere). Phoenix targets the vicinities of nearby, sun-like stars that are considered most likely to host planets capable of supporting life. 

Project Phoenix is yet to receive an intelligent extraterrestrial signal. Many UFO enthusiasts claim that this is because a secret agency or Government has suppressed all of the received signals. However, it is perfectly understandable that we have not received any signals yet due to the limitations of the searches conducted so far. All searches thus far have been very limited in one respect or another. They have generally used equipment that was designed for other purposes and have faced limitations in sensitivity, frequency coverage, types of signals they could detect, and in the number of stars or the directions in the sky that were observed. It is also possible that there are intelligent extraterrestrial civilisations that have methods of interplanetary communication that we have not considered yet. 

This realisation has spurred a SETI Science and Technology Working Group - a team of scientists investigating and planning new directions in SETI searches and systems over the next 20 years. One recent development that has stemmed from this group is Optical SETI, which searches for visible or infrared laser signals. There are currently two Optical SETI programs at UC Berkeley, and other Optical SETI searches are being set up at Harvard and Columbus. 

Project SERENDIP 
UC Berkeley is actually a very active point for SETI, being the home of SERENDIP (the Search for Extraterrestrial Radio Emissions from Nearby Developed Intelligent Populations). SERENDIP began 19 years ago, and was initially located at UC Berkeley's Hat Creek Observatory. Since then, SERENDIP has undergone a series of sequential improvements and has become the world's only "piggyback" SETI system, operating simultaneously with conventional radio astronomy observations. Since 1992, SERENDIP has been piggybacking on the 1000 foot dish at Arecibo Observatory in Puerto Rico - the largest radio telescope in the world (of recent Golden Eye fame and capable of holding 10 billion bowls of corn flakes). In 1996, a major upgrade was made to Arecibo, which coincided with a major upgrade to the SERENDIP piggyback system. 

The end result of the upgrade was that Project SERENDIP was able to monitor more and more stars. But the more stars they could survey, coincided with the need for more processing power to read all the data collected. As Dan Werthimer (chief scientist of the SETI@home team) says, "It's a tech-limited game. The computers are doing the listening, and the more computer power you have, the better job you can do at this." 

Enter SETI@home 
The problem of processing power was entertained in a brainstorm by a former Sun and Starwave employee, who came up with the idea of using a distributed network of idle computers to process the data. SETI@home isn’t the first distributed computing enterprise. For years, groups of encryption enthusiasts have been using the Internet and their computers' idle time to crack codes. Early last year, a networked team of more than 4200 mathematicians found the largest known prime number (which, by the way, contains 909 526 digits). But it is expected that the huge public fascination with life beyond Earth could make SETI@home the biggest project of its kind - "Finding obscure prime numbers is not cool by comparison," says Werthimer. 

The SERENDIP data is recorded on high-density tapes at the Arecibo telescope, filling approximately one 35 Gigabyte tape per day. Because Arecibo does not have a high bandwidth Internet connection, the data tape is sent by airmail to Berkeley, where it is divided into 0.25 Megabyte chunks (called "work-units") on the SETI@home server. These “work-units” are then sent over the Internet to people all around the world to analyse. 

By pursuing the search now, SERENDIP can take advantage of an historical window of opportunity. In only a decade, radio interference from terrestrial sources will grow significantly, and our ability to detect weak signals will be strongly compromised. 

What can you do? 
You can participate in the search by downloading and running the SETI@home client, which downloads and analyses the radio telescope data. On April 6, the UNIX version of the SETI@home client was released and, within a few hours, a couple of thousand people were using the program. The Windows and Macintosh versions are planned for release on May 15. When the software does become available, it can be found at http://setiathome.ssl.berkeley.edu/. If you visit this web page and submit your e-mail address, you will be notified by e-mail when the software is released. 

The software takes the form of a screen saver, and so is activated when you are not using your computer. It downloads a chunk of data from the SETI@home server on the internet, analyses the data, and then reports back to the server with the results. The screen saver is instantly inactivated when you start to use your computer again, and continues analysis when your computer is next available. Therefore the SETI@home software only uses your computer when you are not. You also have the option of controlling when you want your computer to connect to the server. 

A CPU running at 233MHz will take about 24 hours to process a single work-unit (ie. 24 hours of screen saver time), hence the need for as many participants as possible. The software searches for signals about 10 times weaker than the previous SERENDIP search at Arecibo, via a complex algorithm called "coherent integration." This is the first program that has had the computing power to implement this algorithm. 

Most of the signals detected by participants will be from TV stations, radar, microwave transmitters, satellites, astronomical objects, and even "test signals" (which are injected into the system to confirm that the hardware and software are working correctly). However, there is a small but captivating possibility that your computer could be the first one to analyse and detect a signal from another world. If your signal is confirmed and corroborated by follow-up searches, you will be named as one of the co-discoverers of arguably the most important and profoundly impactful signal of all human history. This detection, that would change the world, that would prove that we are neither biologically nor intellectually unique in the cosmos, hasn’t happened yet, but there are many who believe that the day is coming…