Unveiling the Cosmic Mystery: Are We Alone in the Universe, or Do Cataclysmic Challenges Await
Given the absence of aliens, the pressing question emerges: does the Great Filter lie in our past or our future?
With approximately 200 billion trillion stars in the universe and 13.7 billion years elapsed since its inception, one might ponder the whereabouts of alien civilizations.
This forms the core inquiry of the Fermi paradox, the discrepancy between our expectations of potential life in the universe (given habitable planets, etc.) and the reality of only one planet known to harbor an intelligent (albeit debatable) species.
A proposed solution, or rather a framework for considering the issue, is known as the Great Filter. Originating from Robin Hanson of the Future of Humanity Institute at Oxford University, the argument posits that the absence of observed technologically advanced alien civilizations suggests a formidable barrier to the development of life or civilization, hindering them from reaching a stage where they make significant, detectable impacts on their environment – impacts we could observe from Earth.
“You start with billions and billions of potential seeds for life, and you end up with a total of zero extraterrestrial civilizations that we can observe,” elaborates Nick Bostrom, also of the Future of Humanity Institute. “The Great Filter must therefore be sufficiently powerful – meaning, the critical steps must be improbable enough – that even with billions of attempts, one still ends up with nothing: no aliens, no spacecraft, no signals, at least none that we can detect in our vicinity.”
Hanson proposed stages that life may need to traverse (or conditions that must be met for life to arise and endure) in order to progress beyond our current state. These include:
The right star system (including organics)
Reproduction (e.g., RNA)
Simple (prokaryotic) single-cell life
Complex (archaeatic & eukaryotic) single-cell life
Tool-using animals with large brains
Our current state
“The Great Silence suggests that one or more of these stages is highly improbable; there exists a ‘Great Filter’ along the path from inert matter to flourishing life,” Hanson wrote in the original paper. “The overwhelming majority of entities that embark on this journey fail to complete it. Indeed, among the billion trillion stars in our universe’s history, nothing has traversed this path entirely.”
Scouring the galaxy for star systems conducive to life, stars hosting planets, and planets sustaining biospheres and technosignatures could provide insights into the location of the Great Filter. Might it be that the conditions for even simple life are rare (though organic compounds found in asteroids suggest otherwise), or that civilizations encounter different barriers later on, such as an oxygen bottleneck hindering intelligent species from advancing beyond the Stone Age? Alternatively, could the Great Filter lie somewhere between our current state and the colonization of other civilizations? If so, it implies that the filter (likely our own extinction, unless other factors explain the silence of colonizing civilizations to us) awaits us in the future.
The encouraging news is that discovering life on other planets could shed light on our position relative to the Great Filter or our own extinction.
“Searching for technosignatures alongside biosignatures would yield crucial insights into the trajectory of our civilization. If planets with technosignatures abound, we can infer that the most challenging stage in planetary evolution – the Great Filter – likely lies in our past,” as one paper elucidates. “However, if life is prevalent while technosignatures remain absent, it would suggest that the Great Filter looms ahead, poised to confront us.”
It’s plausible that common threats, such as asteroids, obliterate civilizations before they have the chance to embark on galactic colonization, or that at a certain juncture in a technological species’ development, they inevitably stumble upon some perilous technology (such as nuclear weapons, or another concept yet undiscovered), or that some other menace lurks, targeting technologically advanced species reckless enough to broadcast their existence. In one way or another, time will reveal the answers.
Source: Unveiling the Cosmic Mystery: Are We Alone in the Universe, or Do Cataclysmic Challenges Await?