The more we discover habitable planets around other stars of the Milky Way, the less we can not help wondering why we have not yet detected evidence of extraterrestrial civilization. While their technology may be too subtle or too sophisticated, the disappointing silence of the sky may also indicate that the civilizations out there simply do not use technologies that would make them visible to our telescopes.
Based on our own experience — how can we blame ourselves? We indeed expect other civilizations that may exist out there to be much older than ours and therefore technologically advanced. But it might also be possible that a simpler way of life than scientific prosperity has dominated the political landscape on other planets, leading to ancient, but technologically primitive, civilizations.
After all, human history allows us to imagine the possibility that under a different political scenario, our planet could have remained dominated by the anti-scientific mentalities of the Middle Ages. Such a scenario is imaginable on time scales of several thousand years. Though we were fortunate to see the emergence of technology, environmental or political catastrophes could have easily reset the clock of evolution.
Perhaps the ultimate lifespan of human civilization will prove shorter than it would have been if we had remained technologically primitive. Technology poses long-term risks to our future in the form of climate change and unconventional wars (nuclear, biological or chemical). In this case, the surfaces of other planets could reveal relics of technologically advanced, self-destructed civilizations. The problem with this hypothesis is that we can not just imagine it, we must be able to observe it. If we do not detect anything through our telescopes, the only way to know if a civilization is advanced or technologically primitive is to go directly to the spot. Complicated. But if this is ever the case, then astrosociology could become a particularly exciting field of exploration once Man has ventured into space.
Remote observation can only detect civilizations transmitting electromagnetic signals, or altering the atmosphere of their planet by pollution. industrial. If the extraterrestrials do not radically change their natural habitat or transmit artificial signals, we will never be able to know they exist if we do not visit their domestic planets to discover their existence.
An ancient but primitive civilization could indeed settle perfectly into its natural environment for a variety of reasons. Camouflage, for example, is a natural survival tactic, so a civilization might prefer to appear indistinguishable from other life forms, such as vegetation. One could also imagine a civilization so intelligent that it would decide to deliberately maintain a discrete technological profile to support its biosphere.
A first project funded significantly to visit another global system, Breakthrough Starshot, was inaugurated in 2016. Starshot aims to reach the nearest stars in a few decades. Since Proxima Centauri is only 4.24 light-years away, this requires a technology that can accelerate a spacecraft to at least a fifth of the speed of light. The only appropriate concept involves a light sail (to which the payload is attached) pushed by a powerful beam of light. The disadvantage of achieving such speed with this design is that braking near the target planet is still very complicated, even on paper.
So, technologically advanced or primitive civilization? Spoiler Alert: We will probably never know, certainly not in our lifetime.