For nearly half a century, scientists have combed deep space for signs of other intelligent beings, but only on the movie screen have the creatures come to life. The massive Arecibo radio telescope—the world’s largest—has been the central instrument in the longest-running search for radio signals from alien civilizations.
On a given day, highly trained astronomers use the 1,000-foot diameter dish recessed in a sinkhole near the Puerto Rican town of Arecibo, to study the characteristics of our solar system, search for uncomfortably close asteroids, survey vast swaths of the universe and study pulsars, for instance. Radio telescopes like Arecibo pick up and transmit radiation at the low end of the electromagnetic spectrum, which includes invisible radio waves.
A decade ago, researchers at the University of California, Berkeley's Space Sciences Laboratory launched a citizen-science program called SETI@home (SETI stands for search for extraterrestrial intelligence) that sifts through enormous amounts of Arecibo ’s data to detect signs of extraterrestrial life. SETI@home says it has signed up more than 5 million volunteers and boasts 170,000 devoted users clicking away on some 320,000 home computers—the largest community of dedicated users of any Internet computing project.
Now with a number of upgrades, including the recent addition of new and more-sensitive receivers and better frequency coverage, Arecibo is generating 500 times more data for the project than before, and SETI@home needs more desktop computers to help crunch the data. Lots more.
"The next-generation SETI@home is 500 times more powerful than anything anyone has done before," said project Chief Scientist Dan Werthimer. "That means we are 500 times more likely to find ET than with the original SETI@home."
Since 1992, Werthimer and his team have piggybacked on Arecibo astronomy observations to record signals from space and analyze them for patterns that could indicate they were transmitted by an intelligent civilization. When incoming data overwhelmed the computing ability to analyze it, the scientists came up with a plan to harness many computers into one big supercomputer to do the analysis. Most are now on a platform called BOINC (Berkeley Open Infrastructure for Network Computing) developed by SETI@home's director David Anderson so the various projects could share resources.
According to project scientist Eric Korpela, the new data amounts to 300 gigabytes per day, or 100 terabytes (100,000 gigabytes) per year, about the same amount of data stored in the U.S. Library of Congress. "That's why we need all the volunteers," he said. "Everyone has a chance to be part of the largest public-participation science project in history."
Bona fide science experiments that elicit the public’s help in gathering or analyzing data range from spotting aliens to counting butterflies to generating endless prime numbers. According to Werthimer, 42 such projects, mostly based at universities, currently use BOINC. With free software from the Web site (setiathome.berkeley.edu), users can run SETI@home on commercial operating systems.
Essentially a screen saver that kicks in and crunches radio data when your desktop computer is idle, the program breaks data into small chunks and then searches through it for patterns that may indicate a deliberate broadcast from a distant civilization. The computer sends a summary of the interesting stuff back to the Berkeley machine, gets another data chunk and so on.
But what does an alien transmission look like?
"Earthlings are just getting started looking at the frequencies in the sky; we're looking only at the cosmically brightest sources, hoping we are scanning the right radio channels," Werthimer said. "The good news is, we're entering an era when we will be able to scan billions of channels. Arecibo is now optimized for this kind of search, so if there are signals out there, we or our volunteers will find them."
According to the Web site of The Planetary Society, which calls itself the world’s largest space-interest group, the transmission will likely be in the frequency of hydrogen—1420 megahertz on the electromagnetic spectrum—because hydrogen is the most abundant element in the universe and therefore the Esperanto of intelligent beings. Making a few other assumptions, the end result, or “Wow!” signal, will be a bell-shaped peak at around 1420 MHz over about 12 seconds as the telescope sweeps through the emitting part of the sky and then out of range.