The Fermi Paradox seeks to answer the question of where the aliens are. Given that our star and Earth are part of a young planetary system compared to the rest of the universe — and that interstellar travel might be fairly easy to — the theory says that Earth should have been visited by aliens already.
As the story goes, Enrico Fermi (an Italian physicist) first came out with the theory with a casual lunchtime remark in 1950. The implications, however, have had extraterrestrial researchers scratching their heads in the decades since.
"Fermi realized that any civilization with a modest amount of rocket technology and an immodest amount of imperial incentive could rapidly colonize the entire galaxy," the Search For Extraterrestrial (SETI) said on its website.There isn't any paradox. They are here, and have been here. To read more, click here.