Wow signal
The Wow! signal was a strong narrowband radio signal received on August 15, 1977, by Ohio State University's Big Ear radio telescope in the United States, then used to support the search for extraterrestrial intelligence. The signal appeared to come from the constellation Sagittarius and bore the expected hallmarks of extraterrestrial origin.
Astronomer Jerry R. Ehman discovered the anomaly a few days later, while reviewing the recorded data. He was so impressed by the result that he circled the reading on the computer printout and wrote the comment Wow! on its side, leading to the event's widely used name.
The entire signal sequence lasted for the full 72-second window during which Big Ear was able to observe it, but has not been detected since, despite several subsequent attempts by Ehman and others. Many hypotheses on the origin of the emission have been advanced, including natural and man-made sources, although none of them adequately explains the result. The Wow! signal remains therefore the strongest candidate for an alien radio transmission ever detected.
In 1973, after completing an extensive survey of extragalactic radio sources, Ohio State University assigned the now-defunct Big Ear telescope, then located near the Perkins Observatory in Delaware, Ohio, to the scientific search for extraterrestrial intelligence (SETI), in what would have become the longest-running program of this kind in history.
Over a decade earlier, in a 1959 paper, Cornell physicists Philip Morrison and Giuseppe Cocconi had speculated that any extraterrestrial civilization attempting to communicate via radio signals might choose to do so using a frequency of 1420 megahertz, which is naturally emitted by hydrogen, the most common element in the universe and therefore likely familiar to all technologically advanced civilizations.
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