Possible Number of Alien Civilisations That Could Invade Earth Estimated by Scholar

The author of a new paper used the number of invasions perpetrated by countries during the last century to try to gauge the odds of an extraterrestrial civilisation invading our world.

Sending signals into space in search of alien life may not necessarily be a good idea, as there could be about four extraterrestrial civilisations that might invade us, according to a new thought experiment performed by Alberto Caballero, a PhD student at the University of Vigo, Spain.

In a paper titled “Estimating the Prevalence of Malicious Extraterrestrial Civilizations”, which hasn’t been peer-reviewed, Caballero said that he based the probability of an intelligent alien civilisation being malicious on the “probability of humanity posing that same threat to them once it becomes a Type-1 civilization capable of nearby interstellar travel”.

He therefore determined the number of invasions committed by countries on Earth during the past several decades and applied that data to Italian SETI scientist Claudio Maccone's estimation of the number of civilisations that may exist in the Milky Way – 15,785.

“An extrapolation from all the invasions that occurred on Earth in the last century shows an estimated probability of 5.52E-8 percent that a messaged extraterrestrial civilization - or a faction of it – would have hostile intentions towards humanity, as well as a total of 0.22 malicious civilizations”, Caballero wrote in the conclusion of his work.

He pointed out, however, that “the estimated probability of extraterrestrial invasion is two orders of magnitude lower than that of a planet-killer asteroid collision”.