By Seth Shostak
SETI Institute

“At what point would you abandon the search?”

That’s a question I get relatively frequently from folks who think that SETI may be a quixotic quest, as futile as searching for the Seven Cities of Gold. After all, modern efforts to find signals from extraterrestrial transmitters are now in their fifth decade. Could it be that those of us who still hope to tune in other worlds may be missing some writing on the wall? Some dead-obvious, chiseled text with a simple, if disappointing message: “There are no aliens”?

The question seems fair, since SETI’s obvious analogs–the historical voyages of discovery made in the centuries following the Renaissance–were completed in considerably less time than SETI has been beating the cosmic bushes. Columbus spent five weeks finding North America (and he wasn’t even looking). Captain Cook, a true paragon of explorers, and a man who mapped places that Europeans didn’t even know were places, never mounted an expedition that lasted more than three years.

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