Searching for extraterrestrial intelligence across a century

Abstract This short paper explores the century-long journey of searching for extraterrestrial intelligence (SETI) with a focus on the radiowave spectrum. Beginning with early experiments by David Todd and Charles Jenkins, who attempted interplanetary communication using radio technology, it traces the historical development of SETI. The paper discusses significant milestones, such as Project OZMA in 1961 and the transition to modern searches, particularly the Breakthrough Listen project, which represents the most comprehensive effort in SETI history. The vastness of the Universe, the potential for life in various planetary systems and the challenges of differentiating between basic life and intelligent life are highlighted. The discussion includes the concept of technosignatures—signals indicative of advanced technology—and the advancements in telescope technology like the Square Kilometre Array Observatory (SKAO) that enhance SETI capabilities. Recent developments are also addressed, such as an intriguing signal detected in 2020 and the future of SETI is envisioned, including the possibility of building a radio telescope on the far side of the Moon to escape interference from human technosignatures as humans continue to expand into space.