The search for extraterrestrial intelligence began with a project by Carl Sagan himself, the multidisciplinary scientist who disseminated science through the television series Cosmos, founder of the planetary society and co-author of the messages sent on the gold plates aboard the waves. Pioneer and the golden disks aboard the Voyager probes targeting intelligent extraterrestrial beings, as well as the radio message sent to a star cluster from the recently destroyed Arecibo radio telescope.
The SETI organization, by its acronym in English, means search for extraterrestrial intelligence and since its foundation in 1984 it has been dedicated to observing the sky and analyzing data from optical telescopes and radio telescopes to search for traces of intelligent life up there, it was created as a scientific response backed by Nobel Prize winners to analyze strange signals that could be evidence of extraterrestrial life capable of communicating by radio, such as the famous Wow signal detected in 1977 with the Ohio State University Big Earth radio telescope that has not yet been detected. Found a convincing explanation.
And more recently in 2019, looking in the direction of the nearest Centauri Star, the closest to our solar system, a suspicious signal was found that they called BLC1, which seemed to have all the ingredients of extraterrestrial technology.
First; its frequency was very narrow, which is unusual because stars emit radio at a much broader frequency, indicating that it could be an artificial source of radio.
Second; the signal appeared and reappeared in periods of several hours and third, the signal slipped to one side through the frequency spectrum, indicating the Doppler shift produced by a radio emission source moving with respect to our planet.
This obviously raised expectations because we know that in the next few centauri there is at least one planet within the habitable zone, so there was a small possibility that this signal could come from a planet inhabited by an intelligent life form that developed the technology necessary to emit radio signals, but this is science, not horseplay and before reaching any conclusion it had to be confirmed.
Many tests were made to the information of this signal, it had been some type of interference caused by some object such as a satellite reflecting a radio signal from the surface of the Earth, that is, us, this, or some military aircraft; it was quite a disappointment; but the information from this signal served as experience for a new study that includes artificial intelligence.