Generations of stargazers through the ages have looked at the night sky and wondered
whether anyone is out there.
In a recent issue U.S. News & World Report included this question as
one of the great mysteries of science. Indeed, it is. In the book Extraterrestrials:
Where Are They?, authors Ben Zuckerman and Michael Hart note that this is "the
question which astronomers are most frequently asked by laymen" (Cambridge University
Press, New York, 1995, p. 1).
Popular culture is fascinated with the idea. This question has spawned hundreds
of films and dozens of television series-The X-Files and Star Trek
and its spin-offs being some of the most popular. Many American cable-television
systems carry the Sci-Fi network, where watchers can tune in to outer-space sagas
almost any hour of the day or night.
The discussion of the quest for life has produced intense interest not only in
the entertainment media. It is a subject of continuing intense scientific inquiry.
Scientists from many nations have systematically been probing the heavens for almost
40 years for signs of intelligent life among the stars.
The search for life out there
The first such project began in America in 1960. The Soviets began searching for
extraterrestrial signals in 1970. These projects have generally been classified under
the term Search for Extraterrestrial Intelligence, or SETI.
Listening for radio signals from deep space (radio astronomy) is the usual method
by which astronomers search for life in outer space. Their goal is to intercept and
recognize radio signals originating from intelligent beings. Although simple in theory,
this is a Herculean task because the cosmos constantly hums with radio activity.
As the late astronomer Carl Sagan put it, "there are many natural cosmic radio
sources having nothing to do with intelligent life-pulsars and quasars, the radiation
belts of planets and the other atmospheres of stars . . ." (Cosmos,
Random House, New York, 1980, p. 297).
