The Search for Technosignatures: a Review of Possibilities

TL;DR

This review comprehensively surveys the various proposed technosignatures across different scales, from Earth to the universe, and discusses strategies, challenges, and future directions in the search for extraterrestrial technological signatures.

Contribution

It provides a structured, multi-scale overview of technosignature proposals and explores search strategies, integrating diverse scientific perspectives and emphasizing interdisciplinary approaches.

Findings

Organized technosignature proposals by spatial scales and types.

Identified key search strategies and technological requirements.

Highlighted the importance of multimodal and interdisciplinary approaches.

Abstract

This paper aims to review the diverse range of technosignatures that have been proposed in the literature. We organize the review by scales, starting carefully from Earth, then zooming out to Earth's orbit, the solar system, including the Moon, the Earth-Moon Lagrange points, the inner solar system, the asteroid belt, interstellar objects, the outer solar system, the Kuiper belt, the solar gravitational lens region, and the Oort cloud. We then introduce the Kardashev and Barrow scale before exploring exoplanetary technosignatures, from surface, atmospheric to orbital sources. We next consider stellar technosignatures that may involve massive energy utilization, stellar modification or stellar pollution, and end with a section about compact objects. We then review attempts to detect interstellar communication, and discuss many dimensions of the search space from first principles. Then we consider interstellar travel technosignatures, and end with galactic, extragalactic and universal signatures. We end with a discussion about synergies between biosignatures and technosignatures searches, anomaly detection, multimodal strategies, instruments for detecting technosignatures, how to evaluate and prioritize the search, as well as epistemological issues.