Humanity may be all alone in the Milky Way and it will be hundreds of millions of years before we can make contact with an extraterrestrial civilization. This is the result of a model calculation by four British scientists that has now been accepted for publication in the renowned Astrophysical Journal. On the basis of less fundamental facts about the earth, its history and the universe, they determined why we apparently appeared comparatively early in the history of the universe and what can be deduced from this about extraterrestrial civilizations. The consequences for the search for extraterrestrial intelligence (SETI) seem devastating.
Why are we so early
As the group around the economist Robin Hanson (from whom the concept of the “big filter” originates) from the Future of Humanity Institute (FHI) at Oxford University in their publicly viewable paper explained, basic observations suggest that humanity appeared on the scene fairly early in the history of the universe. Highly developed civilizations are actually most likely on long-lived (exo-) planets, and there rather later. While such planets around the particularly long-lived red dwarf stars could live billions of years, mankind appeared after less than one percent of this period of time. So why so early is the big question. Because extraterrestrial mega-civilizations would suppress such competitor civilization later in history, is their answer.
Their study is based on the concept of “greedy” and “quiet” aliens. “Quiet” civilizations are therefore – like humanity at present – limited to their home planets and difficult to find from outside. According to their calculations, about once per million galaxies emerge from “quiet” aliens into a “greedy” (“grabby”) civilization. It breaks through the borders of its home and expands (astronomically speaking) rapidly over several star systems and finally far beyond. In the areas they populate, they prevent the development of any possible competition. They ruled the entire universe within a few billion years, they have calculated.
Contact for hundreds of millions of years
They assure you that they have calculated all this and more based on the current age of the universe, the fact that we are currently not seeing any traces of a “greedy” civilization and important stages of development of life on earth. Based on these assumptions alone and an assumed expansion at about half the speed of light, they have come to the conclusion that “greedy” aliens currently already control 40 to 50 percent of the universe. Each one will control between 100,000 and several dozen million galaxies, they still write. Humanity could hit one of these in 200 million to two billion years, their numbers show.
Should “greedy” civilizations arise from the “quiet” ones, then the probability of this would have to be “depressingly” low, so that at some point there was only one other (“quiet”) civilization in the Milky Way. The ratio between “quiet” and “greedy” civilizations would have to be 10,000 to 1 for that to be the case. If there is currently only one other “quiet” civilization in our home galaxy, the ratio should even be 10 million to 1. All in all, they admit that the prospects for SETI research are not good. Only if the signs of “greedy” civilizations are more subtle than assumed and their expansion slower, then we might eventually find indications of boundaries between “greedy” civilizations and their surroundings.
[Update 21.09.2021 – 19:40 Uhr] The wording on the most long-lived planets has been made more precise.