Astrophysicist Dan Werthimer is looking for aliens. Or, to be precise, he is listening for them via a modified screen saver for a personal computer. All day long in Werthimer's office at the Space Sciences Laboratory at the University of California at Berkeley, spikes of green, blue, pink, and red pulse across his computer monitor. Each spike represents an incoming radio signal. The higher the spike, the greater the signal's intensity and power. Any sustained peak could be a shout from across the universe. "Why look at goldfish or flying toasters on your screen," says Werthimer, "when you could be doing something that answers the ancient question, Are we alone?"
Listening for aliens used to be a passion limited to folks with the biggest ears--radio telescopes with giant dishes cupped toward the heavens. Indeed, for nearly 40 years researchers like Werthimer have been scanning the cosmos with such high-powered instruments in hopes of stumbling upon an alien broadcast--something akin to an extraterrestrial version of I Love Lucy. The search has been slow and laborious. But what really frustrates Werthimer is that he doesn't have enough supercomputers to sort through the mountains of radio-transmission data they are collecting. Aliens may already have tried to contact us--but their message could be languishing on a hard disk, waiting to be decoded.
Now, thanks to Werthimer, anyone with a personal computer can join the search for extraterrestrial intelligence. Werthimer's brainchild--developed with colleague David Anderson--debuts this month. It's called SETI@home: a data-sorting software program that masquerades as a screen saver. Late this month, the software downloaded off the Internet (http://setiathome.ssl.berkeley.edu) will allow amateur computer jockeys to receive and collate chunks of data from the world's largest radio telescope--the thousand-foot-diameter dish nestled in the hills south of Arecibo, Puerto Rico. SETI@home users don't need to know a thing about astronomy. Nor do they need to know how to look for signals. The program does all the work whenever the screen saver is on.
The SETI@home program--so streamlined, so sophisticated, so economical--is a far cry from the first schemes for communing with aliens. In 1820, German mathematician Carl Friedrich Gauss wanted to announce our presence to extraterrestrial passersby by clearing a huge right triangle in the Siberian forest. His plan was to plant wheat in the triangle, then border each side with a square filled with pine trees. Aliens cruising by would glimpse this sylvan representation of a2 + b2= c2 and know the planet's inhabitants had mastered the Pythagorean theorem. Other visionaries favored more flamboyant displays. In 1840 the Viennese astronomer Joseph von Littrow proposed digging a patchwork of enormous ditches in the Sahara--and setting them aflame with kerosene. Nearly 30 years later the French inventor Charles Cros unveiled a plan to reflect sunlight toward Mars using seven carefully placed mirrors. In theory, amazed Martians would behold the shape of the Big Dipper: a wink of intelligence from nearby Earth.
During the twentieth century the search for aliens has taken on a somewhat more pragmatic approach. In 1959 physicists Philip Morrison and Giuseppe Cocconi suggested that aliens attempting to broadcast a signal would probably do it at a significant spot on the electromagnetic spectrum. One obvious "marker," they concluded, lies at 1.42 gigahertz. That is the point on the spectrum at which energy released from hydrogen, the universe's most abundant element, shows up. Morrison and Cocconi argued that there was a practical reason aliens might choose to broadcast signals on a "channel" close to such a universal marker. That region of the spectrum gets little interference from other kinds of natural electromagnetic radiation.
