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Search for Extraterrestrial Intelligence

SETI (Search for Extraterrestrial Intelligence) is a scientific investigation that seeks evidence of life in the universe through signs of its technology. It's based on the observation that the conditions that led to intelligent life arising on Earth could easily be replicated on other planets around other stars, and, given the enormous number of stars in our galaxy alone (estimates range from 100 to 500 billion stars), it's statistically likely that other intelligent beings could be out there.

Most SETI experiments use the tools of radio astronomy to listen for intelligently created radio transmissions. These transmissions could be intentional--beacons created to call attention to the sender--or they could be signals intended for local use that have “leaked” into space. Our own television and FM radio transmissions constantly beam out into space, signaling our presence to nearby stars.

Modern SETI began in 1959, when Cornell physicists Giuseppi Cocconi and Philip Morrison published an article in Nature about using microwave radio to communicate between stars. In the spring of 1960, astronomer Frank Drake spent two months observing two nearby, sun-like stars with an 85-foot radio telescope at Green Bank, West Virginia. This was the first radio SETI experiment. Since then, a number of observations have been carried out around the world, using a variety of techniques. Some target individual stars; others survey large segments of the sky.

The arguments for the existence of extraterrestrial intelligence have recently been bolstered by new findings in two fields. The first is the discovery of “extremophiles”--simple organisms that live in extreme conditions on Earth, such as deep underground in very hot environments, or in very acidic environments. The existence of these creatures gives credence to the idea that life tends to arise wherever possible and under a wide variety of circumstances. The second area of science of great importance to SETI is the ongoing discovery of extra-solar planets, starting in 1989 when giant planets were observed around the stars HD 114762 and Alrai. (Note that these planets were not directly imaged, but inferred by measuring changes in the radial velocity of these stars.) Every year, more and more planets are found around other stars, including main sequence, sun-type stars. Planets, the most likely home of life, are apparently also quite common in our galaxy.

Current SETI observation generates an enormous amount of data that must be analyzed by computers to sift out possible intelligent signals. Much of this work is performed by a volunteer corps of people who donate time on their personal computers, making use of a grid computing program called SETI@home. SETI@home sends small chunks of data out to be processed by volunteers, then collects the results.

SETI programs were established by NASA in the late 1970s, but lost funding in 1992. Since then, the majority of SETI work has been carried out by universities and private institutions such as the SETI Institute. Currently the SETI Institute is constructing a new radio telescope, the Allen Telescope Array, which will be the first instrument with SETI as its primary purpose. When complete, it will allow an enormous increase in SETI observing power.

External Links

• SETI@home Official Site