Soriano's team has been trying to answer the Fermi paradox: the discrepancy between the strong likelihood of the existence of intelligent alien life and the absence of any visible proof of it.
The scientists' calculations show that the percentage of intelligent extraterrestrial civilizations among the total possible number of aliens would be extremely small — about 0.5 percent. This, according to the scientists, explains why we do not observe them today.
The search for their tracks will be possible only in the future, when a greater number of Earth "twins" are discovered by NASA's advanced space telescopes, Soriano believes.
Some experts are confident that the emergence of intelligent aliens is closely related to unique living conditions, which have been found only on Earth. Other astronomers believe that we can't communicate with aliens because galactic civilizations either disappear too fast to be noticed or because they actively hide the fact of their existence from humanity.