Alien civilizations may have slowly wiped themselves out, or been wiped out by climatic catastrophes on their own planets. In a new document published on the ArXiv pre-press web server (I link it here), a group of NASA scientists analyzed the "Great Filter" theory, which postulates that ancient alien civilizations may have wiped out before coming into contact with us. This would explain why we are currently alone in the universe.
The new workshop serves as a warning, and paints the picture of a universe that has been home to many civilizations, few of which long-lived enough to become interplanetary species.
Does climate change solve the Fermi paradox?
The "Great Filter" theory offers the perspective of how entire civilizations may have slowly created the conditions that led to their own demise. And it is, to all intents and purposes, also a possible answer that is not incompatible with the Fermi Paradox (if the alien life intelligent is abundant and widespread, where is everyone? If we are not alone, why do we seem so?).
Let's say, the researchers reflect, that an existential disaster strikes us as our society moves towards space exploration. We would be wiped out before we could meet another civilization. And this may have happened to other civilizations as well, everywhere. More generally, countless civilizations over millions of years, across the universe, have already faced any existential threat we face on Earth (nuclear wars, pandemics, and more) and to which we might succumb.
The Great Filter explains why we are alone
The Great Filter theory was first proposed in 1998 by Robin Hanson, an economist at George Mason University. In a contemporary essay, Hanson wrote that "the fact that our universe appears dead suggests that advanced, explosive, and lasting life is very, very unlikely to arise." Hanson suggested that many alien civilizations may have evolved to a point before they had the technology to expand outside the world, only to then be wiped out. Overflight on optimism (which, however, would be unjustified these days).
In their new paper, NASA scientists argue that evolution is imperative not to succumb to the "Great Filter". "History has shown that competition within the species and, more importantly, collaboration, has led us to the highest peaks of invention," the paper reads. "Yet, we prolong notions that appear to be the antithesis of long-term sustainable growth. Racism, genocide, inequity and more ".
Some say no
Some scientists reject the Great Filter theory because it does not take into account our current limited ability to see the cosmos. After all, as SETI Institute astronomer Seth Shostak says, "we have just begun to search." Any theory that starts from an assumption like "we are alone" is at least premature.
Of course, if we consider the new study as a warning, and as a confirmation that only human collaboration can save our lives, its conclusions must be fully embraced. We are truly alone, in other words, only if we do not help each other. We are truly alone only, to quote Quasimodo, if "in the heart of the earth" everyone is alone.