The Big Ear was a football-fields-sized aluminium radio telescope at Ohio State University — flat reflector, tilted paraboloid, and a strip of Ohio lawn between — that had, by 1977, been reassigned to the longest of long shots: a continuous survey for extraterrestrial narrowband signals, run largely by volunteers on university forbearance. Its search frequency followed the founding logic of SETI: 1420 MHz, the emission line of neutral hydrogen — the universe’s most fundamental radio frequency, the dial-position any signalling civilisation could expect any listening one to monitor. A protected band, too: earthly transmitters are banned there.
On the night of 15 August 1977 the telescope’s fixed beam swept, as the Earth turned, across a point in the constellation Sagittarius, toward the galactic centre. A few days later the volunteer astronomer Jerry Ehman, reviewing the computer printout at his kitchen table, found a vertical string of characters — 6EQUJ5, the printout’s base-36 code for signal intensity climbing to thirty times the background and falling away again over 72 seconds: precisely the rise-and-fall profile a fixed celestial source produces as the beam passes over it. Narrowband, at the hydrogen line, from deep space, shaped like a real source. Ehman circled the column in red and wrote in the margin the word that named it: “Wow!”
Everything checked, nothing returned
The profile ruled out most mundane suspects at a stroke: aircraft and satellites move wrong and are banned from the band anyway; ground interference doesn’t sweep like the sky. The one built-in check failed intriguingly — the telescope’s two feed horns scan the same sky minutes apart, and the signal appeared in only one, meaning it was present in one three-minute window and gone the next. Big Ear re-observed the spot for weeks; Ehman and colleagues, then telescopes vastly more sensitive — the VLA, Green Bank, META, decades of amateur and professional vigils — have returned to those coordinates over and over. Silence, every time.
Candidate explanations have been proposed and mostly buried: a 2017 claim pinning it on hydrogen clouds around two comets was widely rejected on frequency, position, and physics; reflected earthly interference off space debris remains conceivable and unprovable; a 2020s reanalysis suggesting a sun-like candidate star in the beam, and a rival hypothesis involving a rare astrophysical maser flare, keep the literature alive. Ehman himself has stayed the model sceptic — resisting, as he puts it, drawing “vast conclusions from half-vast data.”
So it stands after nearly half a century: the strongest candidate SETI has ever logged, behaving exactly as predicted and never again — either a one-off cosmic coincidence still awaiting its physics, or a lighthouse that swept past us exactly once. The Big Ear itself was demolished in 1998 — for a golf course — which is somehow the most human sentence in the story.