Extraterrestrial life is hypothetical life which may occur outside of Earth and which did not originate on Earth. Such life might range from simple prokaryotes (or comparable life forms) to beings with civilizations far more advanced than humanity.
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 astrobiology.
Since the mid-20th century, active ongoing research has taken place to look for signs of extraterrestrial life. This encompasses a search for current and historic extraterrestrial life, and a narrower search for extraterrestrial intelligent life. Depending on the category of search, methods range from the analysis of telescope and specimen data to radios used to detect and send communication signals.
The concept of extraterrestrial life, and particularly extraterrestrial intelligence, has had a major cultural impact, chiefly in works of science fiction. Over the years, science fiction has introduced a number of theoretical ideas, each having a wide range of possibilities.
Many have piqued public interest in the possibilities of extraterrestrial life. One particular concern is the wisdom of attempting communication with extraterrestrial intelligence. Some encourage aggressive methods to make contact with intelligent extraterrestrial life. Others argue to do so may give away the location of Earth, making an invasion possible in the future.