A new study published in Acta Astronautica provides a probabilistic perspective on the lack of evidence of extraterrestrial technology after 60 years of SETI efforts. The study was conducted by Claudio Grimaldi of the Ecole Polytechnique Federale de Lausanne and the Enrico Fermi Study and Research Center in Rome.
The Search for Extraterrestrial Intelligence (SETI) has been ongoing for 60 years since the first modern experiments by Frank Drake in 1960. Despite major advancements in technology and analysis capabilities, no definitive evidence of alien technology has been found.
Grimaldi approached this lack of evidence from a probabilistic viewpoint. His analysis assumes that technosignatures (like radio signals) are generated randomly at a constant rate across the Milky Way galaxy. Based on 60 years of no detection, Bayesian reasoning provides upper limits on the rate of these technoemissions.
The study concludes that less than 1-5 technoemissions are expected per century across the entire galaxy. This implies a significant probability that the Earth occupies a “void zone” devoid of alien signals. There is a 50% probability Earth will not be illuminated by any technosignals for 60-1800 years.
The analysis makes simplifying assumptions about isotropy and spatial distributions of emissions. It also focuses only on electromagnetic signals like radio waves, not physical artifacts. But the study provides an interesting perspective using the lack of SETI detection as evidence.
Grimaldi suggests the lack of evidence after 60 years does not necessarily mean alien life doesn’t exist. But it does imply SETI searches may find no signals for decades or centuries to come, even with comprehensive all-sky searches.
In the ongoing debate between optimism and pessimism about alien life, this study takes a measured probabilistic approach. The lack of evidence allows statistically constraining possibilities, bridging between extremes. Further SETI efforts will continue testing these predictions. But 60 years of silence provides an intriguing clue about our galactic neighborhood.
