The Wow! Signal
72 Seconds From Deep Space
On August 15, 1977, a radio telescope in Ohio picked up a signal unlike anything recorded before. It lasted exactly seventy-two seconds — the maximum time a deep-space source could remain in the telescope's beam. Volunteer astronomer Jerry Ehman found it in the data days later, circled it in red ink, and wrote one word: Wow!
The signal came from the direction of the constellation Sagittarius. It was narrowband, close to the hydrogen frequency, and thirty times stronger than background noise. It matched nearly every prediction for what an alien transmission would look like.
It has never been detected again. Despite more than a hundred searches over nearly fifty years, nobody has ever explained what sent it.
6EQUJ5
The alphanumeric sequence recorded by the Big Ear telescope. Each character represents a six-second sample of signal strength. The letter U — the peak — means the signal was thirty times stronger than the background noise. No signal like it has ever been recorded before or since.
72 sec
The exact time a point source in deep space would take to pass through Big Ear's beam.
1420 MHz
Near the hydrogen line — the frequency scientists predicted aliens would use.
100+ attempts
Not one has ever detected the signal again.
The Evidence
The Original Data
The sequence 6EQUJ5, circled in red by Jerry Ehman. A 72-second burst of radio energy, narrowband, at the hydrogen frequency. Preserved at the Ohio History Connection — the most famous piece of paper in SETI history.
The Perfect Profile
The signal rose, peaked, and faded over exactly 72 seconds — the precise pattern expected from a distant source passing through Big Ear's fixed beam. This shape ruled out aircraft, satellites, and most ground-based interference.
From Sagittarius
The signal came from the direction of the constellation Sagittarius — toward the dense centre of our Milky Way galaxy, where the concentration of stars is greatest. No known radio source exists at those exact coordinates.
The Story of the Wow! Signal
The Prediction
Physicists Cocconi and Morrison publish a paper arguing that alien civilisations would most likely communicate at 1420 MHz — the hydrogen line. This becomes the foundation of SETI.
Project Ozma
Astronomer Frank Drake points a radio telescope at two nearby stars and listens for intelligent signals. He hears nothing — but the search for extraterrestrial intelligence officially begins.
Big Ear Joins SETI
Ohio State University's Big Ear radio telescope begins scanning the sky for artificial signals. Volunteer Jerry Ehman reviews the data at his kitchen table.
The Wow! Signal
At 11:16 p.m., Big Ear records a 72-second narrowband signal at 1420 MHz from the direction of Sagittarius. It is thirty times stronger than background noise. Ehman finds it days later and writes "Wow!" in red ink.
The Search
Ehman, Robert Gray, and other astronomers conduct over a hundred follow-up observations of the same region. The Very Large Array in New Mexico is used in 1999. Nothing is ever detected again.
Big Ear Demolished
Despite protests, the telescope is dismantled and the land is sold. A golf course and housing development are built where the most famous signal in SETI history was recorded.
The Comet Theory
Astronomer Antonio Paris proposes the signal came from hydrogen gas around a comet. Most astronomers are sceptical — the signal was too strong and too narrow for a comet.
The People in This Story
Jerry Ehman
A volunteer astronomer and former professor at Ohio State University. He found the signal in a stack of printouts at his kitchen table and wrote the most famous annotation in space science. He spent the rest of his life studying what he found.
Robert Gray
A data analyst from Chicago who became obsessed with finding the signal again. He conducted multiple search campaigns, including one using the Very Large Array — one of the most powerful radio telescopes on Earth. He never found it.
Frank Drake
The astronomer who conducted the first SETI search in 1960 and created the Drake Equation — a formula for estimating the number of detectable civilisations in the Milky Way. His work made the Wow! Signal search possible.
The Question That Remains
The signal was real. The data is there. Something happened on August 15, 1977, in the direction of Sagittarius. Something we cannot explain.
Was the Wow! Signal a message from an alien civilisation, a natural phenomenon we haven't discovered yet, or a one-time cosmic accident that we'll never fully understand?
Read the full book to investigate every piece of evidence — then decide for yourself.
Get the Full Book
The complete Wow! Signal mystery. 9 chapters of evidence, theories, and a question only you can answer.
Part of the Ancient Mysteries Volume
Giant drawings visible only from the sky. Books written in languages nobody can read. Machines that shouldn't exist. Real artefacts — no explanations.
See all books in this volume →