On August 15, 1977, The Ohio State University’s Big Ear Radio Telescope detects a powerful 72-second transmission that appears on just one of the telescope’s 50 channels. A few days later, astronomer Jerry Ehman spots the signal in a data printout, circles the sequence “6EQUJ5” and writes “Wow!” in red ink in the margin.
The baffling narrowband signal showed a distinct pattern that started low, grew higher, then decreased. This led to speculation that the transmission had passed over Earth and was celestial in nature. However, scientists could not determine the source of the signal.
Despite repeated attempts to detect the signal by pointing radio telescopes at the same area of the sky, the “Wow!” signal has never been observed again. Its unusual characteristics fueled speculation that it could be a communication from extraterrestrial life, and it became one of the most famous mysteries in the history of search for extraterrestrial intelligence, or SETI.
However, experts generally consider it unlikely that the signal was communication from extraterrestrial life. Other possibilities include a passing comet or a cosmic fluke. A 2024 study that examined archived data from Arecibo Observatory in Puerto Rico proposed the “Wow!” signal could have come from a cold hydrogen cloud. A follow-up analysis of previously unpublished Ohio SETI data in 2025 provided additional support for an astrophysical origin. No definitive explanation has been established.
The Big Ear—which was about the size of three football fields—was dismantled in 1998.
