The SETI@home screensaver project, which allows anyone with a desktop computer to join the search for intelligent life in space, is now the largest computation ever done, on Earth at least.

Since May, over a million people have downloaded the SETI@home screensaver. But, despite an accumulated 50,000 years of computer time, no signs of alien life have yet been found.

The SETI@home program has infiltrated homes, offices and classrooms in 223 countries, "It is truly a phenomenon," said SETI@home project director David Anderson. "One person runs it in an office and pretty soon the whole office is doing it."

Companies large and small (including the BBC) as well as schools and universities have formed groups to compete to see whose computers can analyse the most chunks of data.

The program acts like a screen saver, starting when the computer is idle and analysing data collected from the Arecibo radio telescope in Puerto Rico.

Seti@home is stepping the hunt for alien life

The analysis is done automatically and the results are sent back to the University of California at Berkeley, while participants can see the progress on the computer screen.

Number cruncher

According to Professor Anderson it proves the value of distributed computing and it has encouraged him to look around for other projects that could benefit from this technique.

"SETI@home is now the largest computation ever done on this planet, we have accumulated more than 50,000 years of computing time so far," said project scientist Dan Werthimer, a research physicist at the University of California Berkeley's Space Sciences Laboratory.

"This also is the most sensitive sky survey ever conducted," Professor Werthimer added. SETI@home is so powerful because we are using the world's largest telescope and we are able to use it continuously, 24 hours a day, by piggybacking on other observations."

Of the million people who have downloaded the software about 600,000 have completed at least one unit of data analysis.

Analysts say that the backlog of data from the Arecibo telescope is rapidly disappearing, and Professor Anderson and his team are currently updating the software to analyse the data again to search for more complex signals.