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Why does a lack of SETI detections not prove that extraterrestrial intelligence does not exist?

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artist's conception of Kepler-186f — extraterrestrial intelligence An artist's conception depicts Kepler-186f, the first Earth-sized extrasolar planet found in its star's habitable zone.

The lack of detections by the Search for Extraterrestrial Intelligence (SETI) does not prove that extraterrestrial intelligence does not exist. Astronomers emphasize that the search efforts conducted to date have been extremely limited in scope.1

Comparing the vast number of stars, radio frequencies, and signal parameters to the small-scale nature of SETI projects, experts like Jill Tarter have noted that attempting to determine the existence of extraterrestrial intelligence based on current results is akin to trying to deduce if fish exist in the ocean by dipping a single glass into the water.1

Furthermore, the Drake equation highlights that many variables regarding the prevalence and longevity of intelligent, signaling civilizations remain unknown. Because SETI experiments have only scanned a fraction of the potential search space, the "Great Silence" may simply reflect the immense difficulty of the task rather than the absence of other civilizations.21