A Radio Telescope Hears “Wow!” for 72 Seconds. It Never Hears It Again.

The famous word was written beside the signal, not transmitted by it.

Late on Monday, 15 August 1977, the Big Ear radio telescope in Ohio recorded an unusually strong narrowband radio signal.

Nobody heard a voice.

The telescope's computer printed a sequence of characters representing the signal's measured intensity over time: 6EQUJ5. The characters were not an encoded message from space. They were a compact way of recording how the signal rose and fell above the background noise.

The following morning, volunteer astronomer Jerry Ehman reviewed the printout. He circled 6EQUJ5 in red ink and wrote one word beside it:

Wow!

The name stayed.

The signal lasted 72 seconds—the amount of time Big Ear's fixed observing beam could follow a point in the sky as Earth rotated. Its rise and fall broadly matched the pattern expected from a distant, fixed radio source passing through that beam.

It also appeared close to a frequency associated with neutral hydrogen, a part of the radio spectrum long considered interesting in searches for extraterrestrial intelligence.

That made the observation fascinating.

It did not make it an alien transmission.

Researchers repeatedly searched the same region of sky, but no confirmed recurrence was found. Proposed explanations have included human-made interference, natural astronomical phenomena and other possibilities. None has been established as the final answer.

The signal's origin therefore remains unresolved. Its extraterrestrial origin has never been proved, and 6EQUJ5 has never been decoded because it was not a message to decode.

The episode endures because the evidence is both striking and incomplete: one strong signal, one 72-second passage, one handwritten reaction—and no confirmed second appearance.

The telescope recorded numbers.

The margin supplied the exclamation.