Since hydrogen is the most abundant chemical element in the universe, Cocconi and Morrison reasoned aliens might transmit radio messages across the void in an effort to establish long-distance communication between the worlds.
Drake's ad hoc effort of listening for ET radio broadcasts was called Project Ozma, after Frank Baum's Wizard of Oz's far away realm. Needless to say, no alien broadcasts were ever detected over the months Drake and his Ozma team of astronomers listened to the deep sky.
Since Project Ozma, SETI experiments have continued in the U.S. and elsewhere - also with no results. SETI research remains a hard sell, especially to elected officials doling out public funds.
Public funding for the search for "little green men" has become the third rail of astronomy - witness NASA's short-lived HRMS or High Resolution Microwave Survey Targeted Search Program of 1992-93. HRMS was ridiculed by so many U.S. Congress members that they ended up canceling the effort, just a year after it began, with considerable media-supported flourish.
In the aftermath of the HRMS fiasco, organizations such as the SETI League, and the privately funded SETI Institute of Mountain View, Calif., continue hardcore scientific SETI research . The SETI field has also branched out to include optical SETI, the search for visible alien transmissions - such as laser beams - that might, it's theorized, be a better means of communications over vast distances than radio.
So while you don't hear a lot of news reports about SETI research, it continues. A select group of radio astronomers firmly believe there's intelligent life out there and it's only a matter of time before we make contact.
With the SETI, the question remains: do we really want to contact other intelligent species? Will they be friendly or hostile?
"If we actually manage to communicate with an extraterrestrial civilization, the benefits could be immeasurable," claims Tom McDonough, SETI coordinator for the Planetary Society. "An advanced alien civilization may have solved many of the problems that face us now, such as war, disease, poverty, and environmental destruction. We could learn from their experience."
McDonough's upbeat outlook prevails in the SETI community. On the other hand, advanced alien civilizations may have also solved the problems of eradicating inferior technological cultures that get in their way. When it comes to SETI, astronomers might want to tread lightly before we know if ET is a friend or fiend.
Louis Varricchio, M.Sc., is a former NASA science writer.