The original data that SETI@home analyses comes from the 1,000 foot dish at the Arecebo radio telescope in Puerto Rico. The SETI project can only use the Arecebo telescope at certain times, as other scientific studies of the galaies and stars also use Arecebo. Think of it like booking a local hall for a day - the SETI project can book Arecebo for certain periods but the rest of the time Arecebo is used by other scientists. The first set of data recorded from Arecebo specifically for the SETI@home project was on 20 October 1998.
About 35 Gigabytes of information can be recorded each day from the giant radio telescope.
Most of the SETI (which stands for Search
for Extra Terrestrial Intelligence) research projects in the past used
large computers which analyse data in real time. However, this does
not enable the computers to examine the information in any great depth
to tease out the very weakest signals, nor to look for any great range
of signal types.
This is where your computer comes in. The SETI screensaver is an example of distributed computing. Rather than have a huge supercomputer spend literally thousands of years continuosly processing data, the work is spread out over a large amount of computers. In the case of SETI@home, this amounts to tens of thousands of computers. The work is then done at times when each individual computer wouldn't normally be doing anything at all. Instead of wasting time sitting there doing nothing whilst you are away from your computer, the
SETI screensaver ploughs away at billions of calcuations in the attempt
to find radio signals will indicate the presence of alien intelligence
Along with thousands of others, your computer uses the free SETI at home screensaver to help, in the detailled sifting through the SETI data to try to find alien life. SETI@home performs
one of the most detailled and finely tuned searches ever done - signals
as narrow as 0.07 Hz are analyzed. The aim is to identify patterns
of extra terrestrial signals which have some kind of artificial pattern,
rather than the "random" background cosmic radiation.
The information from the Aricebo telescope
is broken down into manageable chunks or "work units" of around 340Kb.
Each time your computer has completed the analysis of a work unit and needs
another unit to process, the SETI@home program will indicate to you that
it needs to connect to the internet (if you have a dial-up connection. You can also use a setting within the SETI software which will enable your computer to connect automatically if you wish). ADSL broadband users are always connected anyway. The online time taken to send
the results of your analysis to SETI@home's Berkeley headquarters in California
and to download the next work unit is less than 5 minutes with most dial-up modems, and normally less than a minute with ADSL broadband.
After this you can disconnect from the internet (if you're using diall-up) and SET@home is ready to
chug away through literally billions of operations the next time you leave your computer. You don't need to be connected online whilst this analysis is being done.