ABSTRACT

For over 50 years, our civilization has scanned the skies with radio telescopes for signs of signals indicating the existence of intelligent alien life. This search — commonly known as SETI — seeks to answer one of the most fundamental questions: whether we are alone in the universe. Several major SETI efforts have been underway for some years with no definitive detections, which lends itself to one of two classes of conclusions: that either we are unique in our neighborhood or that we haven’t been looking for the right signals. Traditional SETI listens for steady, narrow band signals near where cell phones operate, 1 GHz. In our recent work, we chose to turn the SETI effort around and ask: how would we, on Earth with our foreseeable technologies, build Galactic-scale beacons to attract the attention of extraterrestrials? And if some other civilization were to produce such a beacon, how should we look for it? Our conclusions are that a cost-efficient beacon would be likely to use directed, short pulses at higher frequencies of around 10 GHz with long recurring times. In this model, we suggest that past searches may not have been looking for signals that we, ourselves, would generate, and that future SETI surveys should be designed to look for beacons of this sort.