Broadband Searches for Extraterrestrial Technological Intelligence: a New Strategy To Find Nearby Alien Civilizations

TL;DR

This paper proposes a new, more effective method for SETI searches by modeling extraterrestrial transmitters, utilizing existing astronomical survey data to constrain the prevalence of nearby alien civilizations.

Contribution

It introduces an improved search strategy aligned with general astronomical surveys and uses existing data to set constraints on nearby alien civilizations.

Findings

Existing surveys already constrain the prevalence of nearby alien civilizations.

No alien probes have passed within ~100 light-years of Earth in the past few billion years.

The new method aligns SETI searches with general astronomical survey techniques.

Abstract

One of the most interesting questions that astronomy can hope to answer is: are we alone in our Milky Way galaxy? A detection of an electromagnetic (EM) signal generated by an extraterrestrial technological intelligence, or the presence in our solar system of an alien probe, would answer this question in the negative. Purposeful interstellar communication is a 2-way street - the transmitting and receiving technological intelligences (TIs) both need to do their parts. As the receiving TI, our EM search programs should incorporate a model of what a transmitting TI is likely to be doing. Published searches for extraterrestrial technological intelligence (SETI) have generally not done so and thus have often been suboptimally designed. We propose an improved search technique that more closely corresponds to astronomical surveys that have been undertaken for reasons that have nothing to do with SETI. Published non-SETI radio and optical surveys are sufficiently extensive that they already supply meaningful constraints on the prevalence of nearby purposely communicative alien civilizations. Purposeful communication can also include the sending of spaceships (probes). The absence of evidence for alien probes in the solar system suggests that no alien civilization has passed within ~100 lt-yr of Earth during the past few billion years.