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On August 15, 1977, Big Ear recorded an unusual narrowband signal from the direction of Sagittarius. Six samples covered 72 seconds. The peak was about 30 rms deviations above the baseline, and the profile resembled a source crossing the beam. Ehman circled it and wrote “Wow!”
Wow!
Nearly fifty years later, it has never been detected again.
6EQUJ5
The printed code represents successive intensity ranges. U marks a baseline-subtracted value of 30–31 rms deviations. It is an intensity record, not a decoded message or a comparison with every SETI signal.
30σ
Thirty standard deviations above noise. An unmistakable spike in the data.
100+
Attempts to re-detect the signal over nearly five decades. All unsuccessful.
Sagittarius
A sky direction in Sagittarius, well away from the galactic plane. No star, cloud or transmitter has been securely identified as the source.
The Evidence
The Wow! Printout
The signal that changed SETI history. Jerry Ehman circled the sequence 6EQUJ5 in red ink and wrote "Wow!" in the margin — giving the signal its name. The original is preserved in the Ohio History Connection archives in Columbus.
Big Ear's Design
Big Ear was demolished in 1998 for a housing development. This Kraus-type telescope in Nançay, France uses the same flat-reflector design. The original spanned three football fields of aluminium ground plane with two massive reflectors — one fixed, one tiltable.
The Machine
An IBM 1130 computer processed Big Ear's radio data, dividing incoming signals into fifty channels and printing the results in alphanumeric code. Nobody was listening in real time on August 15, 1977 — the computer recorded it with indifferent precision, and the paper rolled on.
The Signal and the Silence
The Hypothesis
Cornell physicists Cocconi and Morrison propose the hydrogen line (1420 MHz) as the natural frequency for extraterrestrial communication — a "unique, objective standard" that any advanced civilisation would recognise.
The Signal
Big Ear records six narrowband intensity samples over 72 seconds. Their profile resembles the telescope beam response; this makes the event interesting without establishing an extraterrestrial broadcast.
The Search
Follow-up observations revisit candidate fields with different instruments and sensitivities. No confirmed repeat identifies the source. Their limits depend on sky coverage, bandwidth and the time observed.
The Demolition
Big Ear is dismantled after the lease on privately owned land expires. Development plans include housing and a golf-course expansion; Ohio State did not simply sell land it had owned for decades.
A New Theory
Méndez and colleagues propose radiation-triggered hydrogen amplification in 2024. A separate 2025 archival analysis revises inferred properties. The first paper is now listed by the project as accepted in ApJ; neither study identifies the 1977 source.
Key Figures
John D. Kraus
The electrical engineer who designed and built Big Ear. Member of the National Academy of Engineering, inventor of the helical antenna, and director of the Ohio State Radio Observatory. He spent five years constructing the telescope that would one day catch the most famous signal in SETI history.
Frank Drake
Conducted Project Ozma in 1960 — the first systematic search for extraterrestrial intelligence. Creator of the Drake Equation, which estimates the number of communicating civilisations in the galaxy. His work laid the theoretical foundation that led to the Ohio SETI program.
Are We Alone?
The signal lasted seventy-two seconds. The question has lasted forever. Nobody has answered it yet.
But somebody wrote "Wow!" in the margin — and that stubborn human insistence that the universe owes us an explanation might be the most important thing of all.
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Explore the telescope, the unusual detection, the follow-up searches and the question of its origin.