Here's a question I hear quite a bit: why haven't we made contact with intelligent extraterrestrials - ETs?
Physicist Enrico Fermi asked this important question back in the 1940s as a way to demonstrate that we might be alone in the universe - it's now known as Fermi's Paradox. Fermi's Paradox simply states that "the apparent contradiction between high estimates of the probability of the existence of extraterrestrial civilizations and the lack of evidence for, or contact with, such civilizations is a puzzle."
If you discount numerous UFO and alien-abduction stories reported since the late 1940s - some fascinating, but all without a shred of proof - there isn't much reason to suggest that intelligent species exist beyond the Earth. On the other hand, the universe is vast; intelligent civilizations may be widely separated among the less common, Sunlike stars.
The idea of communicating with ETs began in earnest during the 1960s. Researcher Frank Drake, considered the father of SETI astronomy (SETI, short for Search for Extraterrestrial Intelligence), hosted the first SETI astronomy conference in the Appalachian Mountains of West Virginia in 1961.
Around the time of the SETI conference, Drake used the big 26-meter diameter radio telescope of the Green Bank, W.Va., observatory to study two Sunlike star systems: Epsilon Eridani and Tau Ceti.
Following the 1959 suggestion of Cornell University physicists Giuseppe Cocconi and Philip Morrison, Drake had proposed listening to these two nearby stars at the 1,420 megahertz frequency (1 megahertz is one million cycles per second), the so-called magic frequency of the 21-cm line of neutral hydrogen.
This location on the radio dial is now considered the universe's "waterhole" - the radio frequency at which intelligent species might consider a common place to talk and listen, much like the waterholes of Africa where animals come to drink (and humans came to hunt!).
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.