Glossary

SETI

SETI, the Search for Extraterrestrial Intelligence, is the scientific effort to detect signals or other technosignatures from alien civilizations, mainly by scanning the radio sky for narrow, artificial-looking transmissions. Its most famous moment remains the 1977 Wow! Signal, a strong 72-second burst near the hydrogen frequency that has never recurred or been explained. Decades of searches have found no confirmed signal, a silence that frames the Fermi paradox.

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