Since radio astronomers first tuned into the skies, scientists have listened for an elusive radio signal that would confirm the existence of extraterrestrial life. One of the major efforts in the last quarter of the twentieth century was a project termed the Search for Extraterrestrial Intelligence (SETI). Over the years the SETI project evolved into a variety of programs utilizing research resources at a number of different facilities. A number of other programs have embraced at least part of the SETI concept and goals. As of May, 2002, only a fraction of the potential sources of radio signals have been thoroughly observed, and no signal definitively identified as extraterrestrial in origin.

Regardless, there have been a number of interesting possibilities. On August 15, 1977, astronomer Jerry Ehman was going through the computer printouts of an earlier SETI-like project run by Ohio State University (dubbed, "Big Ear"), when he discovered the reception of what remained throughout the twentieth century as the best candidate for a signal that might be classified as a sign of extraterrestrial intelligence. Excited, Ehman scribbled, "WOW!" on the printout and forever after the signal became known as the "WOW!" signal.

Despite repeated attempts to reacquire the signal, the fact that the signal was never again recorded makes many astronomers, including Ehman, skeptical about the origins of the "WOW!" signal. If it were an intentional signal, astronomers argue, the sending civilization would have repeated it—or something like it—many times. A number of SETI experts now assert the "WOW!" signal was, perhaps, a mere reflection of a signal from Earth off an orbiting satellite.

See Also

Astronomy; Cosmology; Electromagnetic Spectrum