The concept of the Great Filter - an argument that attempts to resolve the Fermi Paradox. (or why we haven’t found or been found by alien life DESPITE the existence of hundreds of billions of extrasolar systems in our part of the galaxy. Named after Enrico Fermi who famously quipped on the extraordinary lack of detection of any sign or portent of alien life, much less intelligence, despite avid attempts to locate it.)
The apparent lack of discoverable evidence of alien civilization hints that moving from planetary home to system spanning civilization is a bit rare. The prevailing wisdom is that this really points to the fact that while life might exist elsewhere, intelligent life is stupid unlikely and, even when it does come about, it tends to work itself into extinction. This ‘bottleneck’ for the emergence of alien civilizations is commonly called the Great Filter.
The reason for this bottleneck has been debated for half a century. Reasons include scenarios ranging from the dearth of Earth-like worlds to the improbability of self-replicating molecules and factors like the undisturbed eons of time that are required for prokaryotic life to evolve into eukaryotic organisms.
While the ‘Goldilocks’ view on the rarity of things being just right makes sense, there is just as much likelihood that life could evolve, gain sentience and then just destroy itself before getting too far out of the gate. What evidence do we have of this? Humanity has invested hundreds of thousands of years pulling itself out of the muck of natural catastrophe. It has not yet proven that it has the wisdom to survive much more than a few decades with nuclear, biological/genetic power at its disposal. Advances in technology that are in sight for this century - whether it be unleashing unintended consequences of biotechnology or the relatively unexplored possibilities of super intelligent (and connected) machines have yet to be fully understood...much less harnessed and held safely in control.
With all this in mind, lets cross our fingers and burn incense for the eventual realization that Kepler 186f is a frozen rock with a thin atmosphere filled with ground glass traveling in hurricane winds of 283 mph…or better yet…like the Gliese exoplanets…lets root for it not really existing at all.
Such results will mean we haven’t started the countdown clock of interstellar expansion failure and will give us just a bit longer to get our act together.