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SETI's Home PC Project: Further Details

From: Stig Agermose <wanderer@post8.tele.dk>
Date: Sun, 26 Jul 1998 06:02:29 +0200
Fwd Date: Sun, 26 Jul 1998 03:28:37 -0400
Subject: SETI's Home PC Project: Further Details

From: the July 25 issue of The New Scientist.

URL: http://www.newscientist.com:80/ns/980725/alienscreen.html



First contact
Illustration: Mark Cocks


While you're sound asleep your computer could be hunting for
aliens, says Hazel Muir

AT THE giant Arecibo radio telescope in Puerto Rico, the search
for the murmurs of extraterrestrial civilisations goes on.
Powerful computers hum as scientists scour the sky for signs of
life. But not content with their own computers, they want to use
yours too. The moment you leave your desk, they'll get to work,
tirelessly trawling through their data. And through the night as
you sleep they'll be there, still hunting for alien life.

This is the plan of Dan Werthimer, an astronomer at the
University of California at Berkeley. For 20 years, Werthimer
has been involved in the search for extraterrestrial
intelligence (SETI), and for the past six years he has been
using data from the Arecibo radio telescope to monitor the sky
for signals from alien civilisations. But his team can't search
the telescope's data as thoroughly as they'd like to. "The
search that we do now is limited by computing power," says

And that's where your computer comes in. If all goes well, a new
project known as SETI@home will be up and running by the end of
the year. Werthimer and his colleagues--fellow SETI astronomer
Woody Sullivan and computer scientists David Anderson and David
Gedye--hope to provide more than 100 000 volunteers with
programs to run on their computers at home or at work. Swap your
flying toasters for their alien-hunting screen-saver, and you
could find fame as the proud owner of the PC that brought
extraterrestrial life into view for the very first time.

On a shoestring budget of $100 000 a year, Werthimer's SETI team
can do little more than look over other astronomers' shoulders
to monitor the sky. They have their own receiver at Arecibo, but
it rides "piggyback" on other radio receivers and can only pick
up signals from places that other radio astronomers are already
watching. So the researchers obtain a random view of the
heavens, typically revisiting a patch of sky every three to six

What they are seeking from this random scan is a message
broadcast by aliens. The receiver continuously monitors
wavelengths of close to 21 centimetres (1420=B74 megahertz).
Clouds of neutral hydrogen atoms emit this wavelength. Because
hydrogen is the most common element in the Universe, some SETI
enthusiasts think that an extraterrestrial civilisation would
see this as the natural choice for broadcasts to their cosmic
cousins. The frequency is also fairly free of noise from Earth.
"It's a good quiet spot," says Werthimer.

Quick look

When the data come back, scientists use computers to sift out
any unusually intense radio signals in a frequency band 100
megahertz wide. But because of the limited computer power, the
search is fairly cursory--it can only alert the team to strong
signals if they are 0=B76 hertz wide. And should ET opt for a
pulsed signal shorter than 1=B77 seconds or longer than 10
seconds, the scientists would be none the wiser.

The plan for SETI@home is to focus on a narrower frequency
range, just 2 megahertz wide, but with 10 times the sensitivity.
"One of the things that we can do with SETI@home is look for
many different kinds of pulsing signals," says Werthimer. With
thousands of home computers joining in the search, the team
could spot alien calls that repeat with a period anywhere from
0=B75 milliseconds to 10 seconds. They will also be able to look
at more signal bandwidths, from 0=B71 to 2000 hertz wide.

Werthimer's team have already designed software that will send
250-kilobyte chunks of data from Arecibo to anyone who
volunteers. With a typical modem, the data would take a couple
of minutes to download. It would take about two days to analyse
the data chunk if the software runs all the time, or maybe a
week or two if it runs intermittently.

In one mode the software will run continuously in the
background, even when you are using your computer. Werthimer
maintains that you will scarcely notice it. "It might just have
a little thing at the bottom of the screen that says SETI@home
is running," he says. But if you prefer, SETI@home can also be
set to kick in whenever the machine is idle. Go off to make a
drink, stare out of the window to think, simply refrain from
pressing any keys for a couple of minutes and the SETI
screen-saver will signal that the program has come to life.

For this mode, there will be a choice of graphics. First comes
what Werthimer calls the "nerd graphics"--scientific graphics
telling you what the software is looking for and the kind of
signals it's finding. Or, if you prefer, there will be a
progress display, showing how much of your chunk of data you've
analysed. Alternatively, you can have the "world view", a map of
the Earth with a little dot showing every alien hunter round the
globe. Lastly there's the sky view, where you see a map of the
stars showing the patch of sky that you're working on.
Superimposed will be the mythological figures of the
constellations, so you can find out if your patch is on the
wings of Cygnus the swan or in Orion's armpit.

When you've finished processing a chunk of data, the software
will ask you to return the results of the analysis.
"Unfortunately, you won't know if you've discovered an
extraterrestrial right then," says Werthimer. Only after a
detailed search back at Berkeley to rule out interference, and a
second look at the same spot of sky, will there be any hint that
your humble PC has captured alien technology at work.

It's not the first time that many different computers have been
used for a common enterprise. For years, groups of encryption
enthusiasts have joined up over the Internet and used their
computers' idle time to crack codes. Earlier this year, a member
of a networked team of more than 4200 number-theory buffs found
the largest known prime number, which contains 909 526 digits.
But the huge public fascination with life beyond Earth could
make SETI@home by far the biggest project of its kind: "Finding
obscure prime numbers is not cool by
comparison," says Werthimer.

Fast work

"SETI is a dream problem for this approach," adds Anderson.
Because data from Arecibo can be chopped into chunks and
analysed independently by individual computers, he says, there's
no need for any slow data swapping. "If computers have to spend
lots of time exchanging data with each other, and not enough
time getting useful work done, it can be slower than doing it on
one machine."

Developing the technology has so far been straightforward, says
Anderson. And around 110 000 people have already signed up to
participate through the SETI@home website. The main bugbear for
the team has been finding the money for the project, which was
originally due to start this spring. It has raised around $115
000, but still needs another $200 000 from corporate sponsors
and interested individuals before it can start.

Werthimer is confident that the funding will turn up by the end
of the year. He's even optimistic that somebody, somewhere, will
pick up the signs of an extraterrestrial community within his
lifetime, whether through SETI@home or some future project. "My
view is that there's life out there," he says. "It would be
really bizarre if we were the only ones."

But would they be ready and willing for conversation, or simply
the extraterrestrial equivalents of amoebas and trees? "We're an
emerging civilisation--we're just getting in the game here,"
says Werthimer. He suspects that many alien communities have had
aeons longer to advance than us: "We're going to get into this
intergalactic web of civilisations who've been
talking to each other for millions of years." n

Further information:
sign up to participate in SETI@home at


From New Scientist, 25 July 1998

=A9 Copyright New Scientist, RBI Limited 1998