Extraterrestrial invasion

Invaders from outer space
Undue influence by extra-terrestrial aliens

Alien invasion or space invasion is a common feature in science fiction stories and film, in which extraterrestrial lifeforms invade the 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.

Source: Wikipedia

One of the most dangerous consequences of the current space programme and the despatch of space craft to other planets is that it provokes the invasion of Earth by extra-terrestrials. Some UFOs are alleged to be associated with such invasions. It is believed that some have been shot down, although this information remains classified.
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