The Milky Way is home to millions of potentially habitable planets – and about four of them could be home to evil alien civilizations that would invade Earth when possible, new research posted in the preprint database arXiv (opens in new tab) suggests.
The new paper, which has yet to be peer-reviewed, poses a specific question: what are the chances that humans could one day make contact with a hostile extraterrestrial civilization capable of invading our planet?
To answer that question, study sole author Alberto Caballero — a PhD student in conflict resolution at the University of Vigo in Spain — first looked back at human history before looking to the stars.
“This paper attempts to provide an estimate of the prevalence of hostile extraterrestrial civilizations through an extrapolation of the likelihood that we, as a human civilization, would attack or invade an inhabited one exoplanet,” Caballero wrote in the study.
Related: 9 things we learned about aliens in 2021
(Caballero is not an astrophysicist, but he did publish a study on the infamous Wow! signal – a potential sign of extraterrestrial life – in peer review International Journal of Astrobiology (opens in new tab).)
To arrive at his estimate, Caballero first counted the number of countries that invaded other countries between 1915 and 2022. He found that a total of 51 of the world’s 195 nations had launched some kind of invasion during that period. (The US topped the list with 14 invasions during that time.) He then weighted each country’s likelihood of launching an invasion based on that country’s percentage of global military spending. (Again, the US led the way with 38% of global military spending.)
From there, Caballero added up each country’s individual probability of invading, then divided the total by the total number of countries on Earth, resulting in what he describes as “the current human probability of an invasion by an extraterrestrial civilization.” .
According to this model, the probability of humans invading another inhabited planet is currently 0.028%. However, Caballero wrote that this probability relates to the current state of human civilization – and humans are currently incapable of interstellar travel. If current rates of technological advancement continue, interstellar travel would not be possible for another 259 years, Caballero calculated using the Kardashev scale (opens in new tab) – a system that categorizes a civilization’s progress based on its energy consumption.
Assuming that the frequency of human invasions is declining during this period at the same rate that invasions have been declining over the past 50 years (minus 1.15% per year on average, according to Caballero’s paper), then the human race has one 0.0014% probability of conquering another planet if we potentially become an interstellar or Type 1 civilization in 259 years.
That may sound like a very slim chance – and it is, until you start multiplying it by the millions of potentially habitable planets in the world Milky Way. For his final calculation, Caballero turned to a 2012 article published in the journal Mathematical SETI (opens in new tab)in which researchers predicted that up to 15,785 extraterrestrial civilizations could theoretically share the galaxy with humans.
Caballero concluded that fewer than one of the Type 1 civilizations – 0.22 to be precise – would be hostile to humans who make contact. However, the number of malevolent neighbors increases to 4.42 when taking into account civilizations that, like modern humans, are not yet capable of interstellar travel, Caballero said Vice News (opens in new tab).
“I don’t mention the 4.42 civilizations in my work because 1) we don’t know if all civilizations in the galaxy are like us… and 2) a civilization like us probably wouldn’t pose a threat to another since we do don’t have the technology to travel to their planet,” Caballero told Vice.
Four hostile alien powers don’t seem to worry much. What’s more, the odds of humans coming into contact with — and then being invaded by — one of these malevolent civilizations are vanishingly small, Caballero added.
“The probability of an extraterrestrial invasion by a civilization whose planet we notify is … about two orders of magnitude lower than the probability of an asteroid collision that annihilates a planet,” he wrote in his paper – adding that asteroids, the planets kill like this doomed dinosaurare 1 in 100 million year events.
Although Caballero’s study is an interesting thought experiment, the author acknowledges that his model has limitations. The probability of invasion is based on a very narrow section of human history and makes many assumptions about the future development of our species. The model also assumes that alien intelligence will have brain compositions, values and feelings of empathy similar to humans, which may simply not be the case, Caballero told Vice.
“I just made the paper based on life as we know it,” he said. “We don’t know the spirit of extraterrestrials.”
And it looks like it’s going to be at least a few hundred more years before we do that.
Originally published on Live Science.
https://www.livescience.com/malicious-alien-civilizations-odds There may be 4 evil alien civilizations in the galaxy