The History of SETI

Speculation about life in the universe has a long and interesting history. Two thousand years ago, Plutarch, a Greek priest, wrote about "collections of matter, some of which are other worlds with their own skies and races of men and beasts." The Church declared the doctrine of the "plurality of worlds" to be heretical in the 11th century, and Giordano Bruno was burned at the stake in 1609 for proposing an infinity of worlds with life on them.

Practical SETI began in 1820, when Karl Gauss suggested planting large tracts of Siberian forest in a graphical demonstration of the Pythagorean theorem. Joseph von Littrow in 1840 wanted to ignite kerosene-filled trenches in the Sahara Desert in an assortment of geometric shapes. Both Gauss and von Littrow thought that these large displays would be visible to intelligent life and would be our first way of communicating our intelligent nature. Neither of these proposals ever came to fruition. At the turn of the century, the eccentric genius Nikola Tesla built enormous 150-foot electrical coils and strained the power production capacity of Colorado Springs in order to send radio signals to extraterrestrials. Tesla thought that he had detected signals from an extraterrestrial civilization, but in fact he discovered the atmospheric phenomenon known as whistlers. Guglielmo Marconi also used his early radio technology to listen for signals from beyond Earth.

Until the 1950s, all SETI efforts were primitive and disorganized. The era of modern SETI was born with a paper by Philip Morrison and Guiseppe Cocconi published in Nature entitled Searching for Interstellar Communications. Later that year, 1959, a young scientist by the name of Frank Drake began Project Ozma. This project, which lasted only a year, used the 85-foot radio telescope of the National Radio Astronomy Observatory to scan across a 400-kHz band of radiation from the two nearest Sun-like stars. Nothing conclusive was found. Since then, dozens of radio SETI projects have been conducted without any convincing sign of extraterrestrial intelligence. Of course, all of these experiments combined have searched only a tiny fraction of our cosmic neighborhood.

One notable radio search involved “The Big Ear”, a radio telescope that was functional at Ohio State University from 1973-1998. In August of 1977, volunteer Jerry Ehman recorded what has become known in SETI lore as the “Wow!” signal. While monitoring the readings coming in from the fifty channels monitored by the telescope, one particular signal was noteworthy. Ehman circled the signal and scribbled a single word, “Wow!”, in the margin next to it. The signal was unusual for two reasons, it was a strong and focused signal and it was intermittent. Unfortunately, no one has ever been able to detect that signal since. Undoubtedly of celestial origin, scientists surmise that it was likely an unknown human space probe.

Most SETI searches of the time were small, privately funded affairs. Things changed when, on October 12, 1992 after two decades of deliberation, NASA provided funding for the most ambitious SETI project ever. The Microwave Observing Project (MOP) searched more of the cosmic haystack in its first five minutes than all previous SETI experiments combined! During the previous two decades, NASA had conducted many workshops investigating the feasibility of a SETI search. Emerging from these workshops and discussion came two main search strategies. The first strategy was a targeted search, entailing the detailed monitoring of nearby Sun-like stars. The other strategy involved scanning of the entire sky, to allow for the possibility of more rare but more powerful signals from across the Galaxy.

MOP was only under operation for one year before the U.S. Congress cut federal funding. Luckily, SETI effort was never fully dependent on NASA money. Two private organizations, the SETI Institute (founded in 1984) and the Planetary Society, were two key players in the preservation of the effort. In fact, taxpayers do not fund many of the current plans at all. Famous corporate leaders and media moguls like Steven Jobs, Paul Allen and Steven Speilberg have provided millions of dollars for a new generation of SETI experiments. Even though Congress has been dubious, the public is entranced by the idea of making contact with intelligence far beyond the solar system. The SETI Institute, a non-profit research lab, has parceled out data from the current radio experiments to millions of people around the country. Each person runs a program that uses spare capacity on their PC to look for artificial signals in a stream of radio noise. In this way, the SETI researchers can harness the power of millions of PCs to look for the elusive evidence of extraterrestrial intelligence.

The new wave of SETI experiments depends on powerful receivers and large telescopes. Previous projects could only search a few hundred different frequency channels simultaneously. Projects like MOP listen in on tens of millions of channels simultaneously. The modern digital age and custom integrated circuits have made the improvements in the search possible. The receivers used for signal detection are also extraordinarily more sensitive. Astronomers achieved a radio detection of the weak signal of Pioneer 10 after it left the solar system; the detection had a changing Doppler shift due to the Earth's rotation. The waning signal has the equivalent power of a single Christmas tree light at a distance of over 5 billion miles! The 1000-foot diameter radio dish at Arecibo in Puerto Rico offers even greater sensitivity. The dish is so large that it could hold 357 million boxes of corn flakes or all the beer consumed on Earth in one year. Detectors at the focus of the Arecibo dish could detect a ½ megawatt radio signal, equal to the strength of a modest radio station on the other side of the Milky Way.

Bigger, better, and more ambitious SETI schemes are underway. Two projects in particular, the Allan Telescope Array and Optical SETI, promise to catapult SETI efforts to an all-new high. Even loftier project could be further in the future. For instance, it could be possible to send a beacon and receiver hundreds of A.U. from the Earth and use the Sun as a gravitational lens to amplify and direct signals to distant targets. Future telescopes in space will allow the spectroscopic analysis of the reflected light from planets in other stellar systems. The direct detection of atmospheric chemistry that indicates life would cut through the web of anthropocentric arguments regarding technology and radio communication. In the meantime, researchers must think as broadly as possible about the nature of life. The search for life in the universe will become a truly scientific subject one step at a time.

Few scientific subjects generate as strong an emotional response as SETI. Debates between SETI optimists and pessimists can be acrimonious. Pragmatists argue that the scientific basis for the optimistic calculations is flimsy and that no search strategy can be logically justified. SETI has been unpopular with some politicians, who see it as a frivolous use of taxpayers’ money. NASA has had considerable trouble in funding SETI, despite the fact that it accounts for less than 0.1% of the agency's science budget. However, popular support for SETI remains strong. "The probability of success is difficult to estimate," wrote physicists Giuseppe Cocconi and Phillip Morrison in their 1959 paper, "But if we never search, the chance of success is zero." Few people can resist the excitement of one of the most profound questions humans can ask, what is our place in the universe?

Work Cited:

The Search for Extraterrestrial Intelligence: A Short History http://www.planetary.org/html/UPDATES/seti/history/History00.htm
The History of SETI, http://www.seti.org/site/pp.asp?c=ktJ2J9MMIsE&b=178911


Copyright © 2000-2008 Authors/Editors Chris Impey & Erika Offerdahl
Do not reproduce without permission from Chris Impey.