wow-signal

On August 15, 1977, a radio telescope in Ohio detected a signal so precisely matched to the expected frequency of extraterrestrial contact that the astronomer who found it circled it in red ink and wrote one word. The signal never repeated. Nearly five decades later, astronomers still cannot fully agree on what caused it.

The search for extraterrestrial intelligence (SETI) has listened for technological signals since Project Ozma in 1960. It now spans radio telescopes, laser searches, and surveys for other technosignatures. No confirmed signal has been found, and the best-known candidates, from the 1977 Wow! signal to BLC1, remain unexplained or were traced to interference.