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.[1]
Origins
In 1892, Robert Potter, an Australian clergyman, published The Germ Growers in London. It describes a covert invasion by aliens who take on the appearance of human beings and attempt to develop a virulent disease to assist in their plans for global conquest. It was not widely read, and consequently H. G. Wells' vastly more successful novel is generally credited as the seminal alien invasion story.[2]
In 1898, Wells published The War of the Worlds, depicting the invasion of Victorian England by Martians equipped with advanced weaponry. It is now seen as the seminal alien invasion story and Wells is credited with establishing several extraterrestrial themes which were later greatly expanded by science fiction writers in the 20th century, including first contact and war between planets and their differing species. However, there were stories of aliens and alien invasion prior to publication of The War of the Worlds.[2]
Wells had already proposed another outcome for the alien invasion story in The War of the Worlds. When the Narrator meets the artilleryman the second time, the artilleryman imagines a future where humanity, hiding underground in sewers and tunnels, conducts a guerrilla war, fighting against the Martians for generations to come, and eventually, after learning how to duplicate Martian weapon technology, destroys the invaders and takes back the Earth.[3]
Six weeks after publication of the novel, The Boston Post newspaper published another alien invasion story, an unauthorized sequel to The War of the Worlds, which turned the tables on the invaders. Edison's Conquest of Mars was written by Garrett P. Serviss, who described the famous inventor Thomas Edison leading a counterattack against the invaders on their home soil.[4] Though this is actually a sequel to Fighters from Mars, a revised and unauthorised reprint of War of the Worlds, they both were first printed in The Boston Post in 1898.[5]
This is a familiar variation on the alien invasion theme. In the infiltration scenario, the invaders will typically take human form and can move freely throughout human society, even to the point of taking control of command positions. The purpose of this may either be to take over the entire world through infiltration (Invasion of the Body Snatchers), or as advanced scouts meant to "soften up" Earth in preparation for a full-scale invasion by the aliens' conventional military (First Wave). This type of invasion represented common fears of the American public during the Cold War, particularly the fear of infiltration by communist agents.[7]
Beneficial alien invasion
In Henry Slesar's 1958 story The Delegate from Venus, an alien robot cautions that Earth will be destroyed if its people do not learn to live in peace.
This theme has also been explored in fiction on the rare occasion. With this type of story, the invaders, in a kind of little grey/green man's burden, colonize the planet in an effort to spread their culture and "civilize" the indigenous "barbaric" inhabitants or secretly watch and aid earthlings saving them from themselves. The former theme shares many traits with hostile occupation fiction, but the invaders tend to view the occupied peoples as students or equals rather than subjects and slaves. The latter theme of secret watcher is a paternalistic/maternalistic theme. In this fiction, the aliens intervene in human affairs to prevent them from destroying themselves, such as Klaatu and Gort in The Day the Earth Stood Still warning the leaders of Earth to abandon their warlike ways and join other space-faring civilizations else that they will destroy themselves or be destroyed by their interstellar union. Other examples of a beneficial alien invasion are Gene Roddenberry's movie The Questor Tapes (1974) and his Star Trek episode "Assignment: Earth" (1968); Arthur C. Clarke's Childhood's End,[8] the novel (later anime) series Crest of the Stars, the film Arrival (2016), and David Brin's Uplift Universe series of books.
Seth Shostak, senior astronomer at the Search for Extraterrestrial Intelligence (SETI) believes an alien invasion of Earth to be unlikely for several reasons. He believes that any resources available on Earth can be found on their home planet, or that it would be easier to locate or create it on their own. He also believes that, if alien life were to make contact with Earth, it would first be through robots rather than the aliens themselves.[10]David Morrison, Director of Space at NASA-Ames Research Center argues that first contact would be in the form of radio communication rather than visitation.[10]
^Peter, Lev (2006-11-06). Transforming the screen, 1950-1959. History of the American cinema. Vol. 7. University of California Press. p. 177. ISBN0-520-24966-6. Invasion films were common in the 1950s featuring a variety of aliens portrayed as superior to earthlings both in intelligence and technology. In these films, aliens represent what some Americans feared about the Soviets. Invaders, friends or enemies, and often with the help of robots, either come to warn earthlings or destroy them with superior technology. Sometimes, the invaders use the strategy of infiltration, taking over the minds of the people, making slaves of them or appropriating their bodies, thus making war unnecessary. In some instances, the aliens already had a similar appearance - in Star Trek, while officially made contact with Humanity in 2063, (and were not "invaders" - some were shipwreck survivors, others time-travelers, accompanied by at least one Human, from a future where their respective worlds were allies) no fewer than six Vulcans had spent some time on Earth, passing as Human simply by using hair or skullcaps to conceal their pointed ears.
