Updated: June 29, 2024

Extraterrestrial life, also called alien life ( or, if it is a sentient or relatively complex individual, an "extraterrestrial" or "alien" ), is life that does not originate from Earth. These hypothetical life forms may range from simple single-celled organisms to beings with civilizations far more advanced than humanity. Although many scientists expect extraterrestrial life to exist in some form, there is no evidence for its existence to date. The Drake equation speculates about the existence of intelligent life elsewhere in the universe. The science of extraterrestrial life in all its forms is known as exobiology.

Since the mid-20th century, there has been an ongoing search for signs of extraterrestrial life. The search encompasses a search for current and historic extraterrestrial life, and a narrower search for extraterrestrial intelligent life. Reflecting the category of search, methods range from the analysis of telescope and specimen data to radios used to detect and send signals of communication.

The concept of extraterrestrial life, and particularly extraterrestrial intelligence, has enjoyed a major cultural impact, chiefly including works of science fiction. Over the years, science fiction both communicated scientific ideas and influenced public interest and perspectives of extraterrestrial life. One shared space is the debate over the wisdom of attempting communication with possible extraterrestrial intelligence: Some encourage aggressive methods to try for contact with intelligent extraterrestrial life, whereas others argue that it might be dangerous to actively call attention to Earth.

( * ) Special thanks to, "Guy Foster" for many of the photos for this gallery!!!