A 72-second burst on the quietest channel in the sky. It has never repeated.
THE WOW! SIGNAL PRINTOUT · BIG EAR RADIO OBSERVATORY · PUBLIC DOMAIN
The known landscape
In 1977, a radio telescope listening for extraterrestrial signals recorded a 72-second burst so strong the astronomer on duty circled it on the printout and wrote "Wow!" in the margin. It has never repeated.
The signal arrived at almost exactly the frequency reserved for neutral hydrogen, the quietest and most "natural" channel to broadcast on. It matched the shape expected of a real astronomical signal sweeping through the telescope's field of view, not equipment noise.
The edge
Decades of searches at the same coordinates have found nothing. Every proposed terrestrial or natural explanation — comets, satellites, reflected signals — fails to account for one detail or another, and none has been confirmed.
Contemplative inquiry
Was it a one-time transmission, a natural event we don't yet understand, or something we simply weren't listening for again in time? Would we recognize a repeat if it came from a slightly different direction?