We know now, the Milky Way home to billions of planets. Among them, many are potentially habitable. But what we still don’t know is how many are actually inhabited? And among them, how many could carry hostile extraterrestrial civilizations? Civilizations which could nourish against us desires of invasion. Four, replies Alberto Caballero today, a researcher at the University of Vigo (Spain) already known for his work on the mysterious signal ” wow! “.
To reach this conclusion, the researcher literally put himself in the shoes of these extraterrestrials. More precisely, he considered the probability that our own human civilization would attack an inhabited exoplanet. From there, he extrapolated an estimate of the prevalence of the extraterrestrial civilizations hostile.
Alberto Caballero first counted how many invasions had taken place on Earth between 1915 and 2022. Then he weighted each country’s probability of launching such an attack by global military spending. And added each country’s probability of triggering an invasion. Finally, he divided it all by the total number of countries on Earth. To get what it calls “the current human probability of invasion by an extraterrestrial civilization”. A low probability, only 0.028%.
Taking into account the observed rate of decrease in invasions on Earth over the past 50 years, Alberto Caballero even estimates that this probability could drop to 0.0014% by the time humanity is ready to embark on an interstellar journey. That is to say, within 260 years!
Many assumptions, few certainties
An extremely low probability. But which takes on another meaning when it is compared to the millions of planets that cross the Milky Way. And even when applied to the number of extraterrestrial civilizations that could populate our Galaxy. Alberto Caballero used the number advanced by researchers in 2012. According to them, there would be up to 15,785 extraterrestrial civilizations in the Milky Way.
Very few of these civilizations could be both hostile and have reached the famous level 1 of the Kardachev scale. A level that allows them to interstellar travel. Not even one – 0.22 to be precise – according to Alberto Caballero’s estimates. But more than four – 4.42 to be exact – could turn out to be both hostile and find themselves in a technological situation comparable to ours.
So should we fear an alien invasion? Not immediately in any case, reassures us the researcher. According to him, we could have sent something like 18,000 messages to the stars so that the probability that we would be attacked by an alien civilization would remain of the order of seeing our Earth hit by a asteroid like the one that ended the reign of the dinosaurs. An event that only occurs every 100 million years on average.
Moreover, it must be recognized that the work of Alberto Caballero — which is more of a thought experiment — concentrates on a part of the history of humanity that is a little too small to be really significant. And that they are based on numerous hypotheses of the development of species. As well as the idea that extraterrestrials share values similar to ours. Which, of course, might not be the case at all. For the worse… as for the best!
Interested in what you just read?