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signal radio project extraterrestrial

Since radio astronomers first tuned into the skies, scientists have listened for an elusive radio signal that would confirm the existence of extraterrestrial life. One of the major efforts in the last quarter of the twentieth century was a project termed the Search for Extraterrestrial Intelligence (SETI). Over the years the SETI project evolving into a variety of programs utilizing research resources at a number of different facilities. A number of other programs have embraced at least part of the SETI concept and goals. As of May 2003, only a fraction of the potential sources of radio signals have been thoroughly observed, and no signal definitively identified as extraterrestrial in origin. As of February 2003, nearly 10% of the visible night sky had never been scanned for signals. Less than 50% of the visible sky had been briefly scanned more than once.

SETI is a term that encompasses several different groups and their efforts to seek out intelligent extraterrestrial life. The driving force behind these groups is the ancient human desire to understand the origin and distribution of life throughout the Universe. As technology progresses, SETI have evolved from single project observations of the night sky to coordinated efforts in data analysis that, as of February 2003, involved more than four million volunteers from around the globe, who had collectively donated more than 1,327,600 years or collective computer CPU time.

Cornell University professor Frank Drake founded the first SETI program in late 1959. Drake reinforced his idea of scanning the skies with his famous Drake Equation. The Drake equation predicts the abundance of intelligent life within a certain galaxy.

The second major development of SETI took shape in the late 1960s when NASA joined the program. NASA was minimally involved the project, but spawned many SETI related programs. These programs included the Microwave Observing Project, Project Orion, the High Resolution Microwave Survey, Toward Other Planetary Systems, and more. One of the most intensive SETI related programs NASA would initiate began in 1992, but Congress cut funding for the program within a year. SETI projects now must rely on private funding, and SETI operates through the SETI Institute, a nonprofit corporation.

Historically, scientists used several different methods for searching for extraterrestrial intelligence. The earliest method, and still most commonly used in present research, is the scanning of electromagnetic emissions. Radio waves are picked up by an array of radio telescopes and scanned for non-random patterns. More modern methods expand the search to other regions of the electromagnetic spectrum, including the infrared spectrum.

As of 2003, the University of California at Berkeley hosts the most widespread SETI effort in history. Berkeley projects include SETI@Home (a distributed computing project), Search for Extraterrestrial Radio Emissions at the Nearby Developed Intelligent Populations (SERENDIP), Optical SETI, and Southern SERENDIP. SETI@Home collects its data in the background of the Arecibo Radio Observatory and relays it back to the lab in Berkeley. The data is then divided into workunits and sent out to the personal computers of volunteers throughout the world. These personal computers scan the data for candidate signals. If a candidate signal appears, it is relayed back to Berkeley, where the signal is checked for data integrity. Finally, the lab removes radio interference and scans the data for final candidates. The Berkeley faction of SETI will be expanding their efforts with the Allen Telescope Array (formerly known as the One Hectare Telescope) designated specifically for this research.

Project Phoenix, also run by the SETI Institute, concentrates on obtaining signals from targeted areas within our galaxy. The focused Phoenix receiver can amass radio energy for longer periods of time and with greater sensitivity than previous SETI radiotelescopes, allowing for faster and more precise analysis.

Although only a small fraction of the sky has been scanned, so far, SETI initiatives have not confirmed a signal from an extraterrestrial source that is conclusive proof of an extraterrestrial intelligence. A few strong and unexplained signals have intrigued SETI scientists; the most well known was received in 1977 at the Ohio State Radio Observatory. None of the signals have ever repeated.

On August 15, 1977, astronomer Jerry Ehman was going through the computer printouts of an earlier SETI-like project run by Ohio State University (dubbed, "Big Ear"), when he discovered the reception of what remained throughout the twentieth century as the best candidate for a signal that might be classified as a sign of extraterrestrial intelligence. Excited, Ehman scribbled, "WOW!" on the printout and forever after the signal became known as the "WOW!" signal.

Despite repeated attempts to reacquire the signal, the fact that the signal was never again recorded, makes many astronomers, including Ehman, skeptical about the origins of the "WOW!" signal. If it were an intentional signal, astronomers argue, the sending civilization would have repeated it—or something like it—many times. A number of SETI experts now assert the "WOW!" signal was, perhaps, a mere reflection of a signal from Earth off an orbiting satellite.

In March 2003, researchers with the SETI@Home distributed computing project, the largest computation in human history, announced that the 150 highest probability candidate signal sources would be systematically reexamined by the Arecibo telescope in Puerto Rico. The candidate signals were identified over a four year period during which SET@Home participants donated more than a million years of computing time.

The final "stellar countdown" phase of the SETI@ Home project will attempt to further discriminate between signals that are random noise or terrestrial interference and those that might be of extraterrestrial origin. The signals of highest investigative interest were evaluated by several factors, including the number of times the radio source was detected, strength of signal, apparent proximity of origin to known and observable stars, and the type of star and/or presence of known planets near the apparent source of the signal.



McConnell, B. Beyond Contact: A Guide to SETI and Communicating with Alien Civilizations. O'Reilly and Associates, 2001.

Sagan, Carl. Project Haystack: The Search for Life in the Galaxy (Life in the Universe Series). Seti Institute, Teacher Ideas Pr., 1997.


Korpela, E. "SETI@Home—Massively Distributed Computing for SETI." Computing in Science and Engineering Magazine. Volume: 3 Issue: 1 (2001):78-83.


"SETI: Searching for Life." Sky and Telescope [cited February 13, 2003]. <http://skyandtelescope.com/resources/SETI/>.

Lee W. Lerner

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