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Mercury, September/October 2002 Table of Contents

Courtesy of Don Davis.

by Ben Zuckerman

The union of space telescopes and interstellar spaceships guarantees that if extraterrestrial civilizations were common, then someone would have come here long ago.

Where do humans stand on the scale of cosmic intelligence? For most people, this question ranks at or very near the top of the list of "scientific things I would like to know." Lacking hard evidence to constrain the imagination, optimists conclude that technological civilizations far in advance of our own are common in our Milky Way Galaxy, whereas pessimists argue that we Earthlings probably have the most advanced technology around. Consequently, this topic has been debated endlessly and in numerous venues.

Unfortunately, significant new information or ideas that can point us in the right direction come along infrequently. But recently I have realized that important connections exist between space astronomy and space travel that have never been discussed in the scientific or popular literature. These connections clearly favor the more pessimistic scenario mentioned above.

Serious radio searches for extraterrestrial intelligence (SETI) have been conducted during the past few decades. Brilliant scientists have been associated with SETI, starting with pioneers like Frank Drake and the late Carl Sagan and then continuing with Paul Horowitz, Jill Tarter, and the late Barney Oliver. Even with all their accumulated talent, these investigators have failed to consider the full implications for SETI of all advanced civilizations possessing space telescopes capable of discovering nearby living worlds. A very likely consequence of such discoveries will be interstellar travel to investigate the nature of alien life forms. The fact that, evidently, no technological creatures have come to investigate Earth during the past several billions of years is strong evidence that few such creatures exist in our galaxy.

Click here to read Seth Shostak's response.