invasion warning

Alien invasion or space invasion is a common feature in science fiction stories and films, in which extraterrestrial lifeforms invade Earth to exterminate and supplant human life, enslave it, harvest people for food, steal the planet's resources, or destroy the planet altogether. It can be considered as a science-fiction subgenre of the invasion literature, expanded by H. G. Wells's seminal alien invasion novel The War of the Worlds, and is a type of 'first contact' science fiction.
Experts consider the prospects of an actual invasion of Earth by extraterrestrials to be extremely unlikely, due to the enormous cost in time and resources.

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