For seventy years, humanity has been listening to the cosmos, hoping to pick up a signal, a code, a breath proving that we are not alone. Yet, despite billions of stars and planets, the silence remains deafening. With the technological progress of recent years, the great Fermi paradox –“Where are they then?”– seems more current than ever.
A team of Iranian physicists from Sharif University in Tehran thinks they have found a less than reassuring explanation: if we see nothing, it may be because advanced civilizations never live very long and die out before being able to contact anyone, summarizes Gizmodo. According to their calculations, taken from a model combining the Drake equation and the real range of radio signals, a technologically developed society would survive on average five millennia. No more.
Five thousand years, a speck on the scale of the cosmos and far too little to have time to probe the universe. If the extraterrestrials have not crossed our path, it is because they may have already disappeared: exhausted, self-destructed, or simply extinct over time. In theory, we should have captured an echo, a vestige, a whisper of civilization, but astronomers are still confronted with total and infinite silence.
A disastrous destiny
The study, published on the scientific site arXiv, suggests that it is not necessary to imagine a cosmic conspiracy or camouflaged extraterrestrials, hidden among us or hidden behind Mars: the simplest scenario is also the most pessimistic. Intelligent life emerges, evolves, invents technology, then dies out before being able to interact with its peers. The cycle begins again elsewhere, too quickly and too far for two civilizations to cross paths. In short: we may not have found the others because they never exist long enough to be found.
So what about us? We will surely have the same fate: the Earth ticks all the boxes for the start of decline. We have been a technological civilization for about 300 years, emitting detectable signals for barely a century. If the galactic average is reliable, we would have around 4,700 years left before reaching the survival limit of intelligent species… but it could also go much faster.
The list of threats drawn up by the researchers resembles a best-of of our contemporary anxieties: asteroid fall, major volcanic eruptions, climate change, pandemic, nuclear war, artificial intelligence gone out of control, there is an embarrassment of choice when it comes to the end of the world. So many scenarios capable of prematurely shortening our stay among the stars, and therefore our chances of being discovered or of discovering another civilization.
The authors do not say that every civilization must necessarily die at 5,000 years – fortunately for us – but the probability that it will cross this threshold seems tiny.
