SETI, the Search for Extraterrestrial Intelligence, is a scientific experiment in which the goal is exactly what it sounds like, to find aliens. This type of research takes many forms, but the variety most likely to be encountered by the average person — assuming they do not actually think they have made contact with little green men — is known as Radio SETI.
Radio SETI works by using radio telescopes to gather radio noise from space and computers search for narrow-bandwidth signals, radio signals which do not occur naturally. Discovery of such signals would indicate the existence of technologically advanced extra-terrestrial entities.
Traditionally, radio signals collected by radio telescopes have been analyzed by dedicated super-computers located at the telescopes themselves. However, the University of California, Berkeley project SETI@home has changed this. SETI@home performs SETI analysis of radio telescope data using individual’s personal computers all around the world networked together using the Internet.
The idea behind SETI@home is that while SETI researchers cannot afford the massive computing costs necessary to build super computers, desktop computers around the world belonging to ordinary people can do the work a small piece at a time.
SETI@home works by accessing a central server when your desktop computer would normally be idle and simply sitting with a screen saver. Thus, instead of just sitting there, the computer is instead processing data for SETI and, hopefully, finding that elusive signal of alien life. When you come back to your computer, the screen saver goes away, as usual, and SETI@home disappears, ceasing to use local resources.
The data that the Berkeley program uses is gathered by the Arecibo telescope in Puerto Rico and then broken into pieces for distribution to individual computers.
The data is then filtered to remove local noise (radio, TV, etc.) so that extraterrestrial signals can be identified. SETI@home has spent most of its time looking for concentrated, high power, narrow bandwidth signals (just like AM or FM radio). However, last year they also began looking for short burst broadband signals with their Astropulse program.
SETI@home celebrated its tenth anniversary last year, although David Gedye first proposed the idea in 1995. For more information on SETI@home or to download it for Mac, Windows or Linux, go to: http://setiathome.berkeley.edu/