Search for extraterrestrial intelligence

Search for extraterrestrial intelligence (SETI) is the scientific effort to detect or communicate with technological civilizations beyond Earth through astronomical observations and related methods.

Radio SETI: The search for extraterrestrial technology by detecting artificial radio signals from space. Radio telescopes can monitor narrowband signals that natural astrophysical sources rarely produce.
Project Ozma: Frank Drake's 1960 search for radio signals from Tau Ceti and Epsilon Eridani. It was the first modern radio SETI experiment.
Technosignature astronomy: The astronomical study of observable effects that may indicate technology beyond Earth. It extends SETI beyond searches for intentional communication.
Fast radio burst: A brief, bright radio pulse originating beyond the Milky Way. These dramatic natural events can resemble the unexpected signals SETI seeks, but are not evidence of technology.
Great Filter: A proposed evolutionary barrier that makes technological civilizations rare or short-lived. It offers one possible explanation for why SETI has found no confirmed signal.
Optical SETI: The search for extraterrestrial technology through brief, intense pulses of visible or infrared light. A powerful laser pulse could be detectable across interstellar distances even when brief.
Frank Drake: An American astronomer who helped establish modern SETI and formulated the Drake equation. His experiments and organizing work shaped SETI's early agenda.
Exoplanet atmosphere: The layer of gases surrounding a planet outside the Solar System. Industrial pollutants or unusual atmospheric chemistry could be investigated as possible technosignatures.
Pulsar: A rapidly rotating neutron star that emits regular beams of electromagnetic radiation. Pulsars initially appeared artificial because their radio pulses were remarkably regular.
Loudest signal fallacy: The mistake of assuming another civilization's strongest detectable emissions are intentionally aimed at observers. SETI sensitivity estimates depend on whether signals are deliberate or incidental.

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