Opinion: Is Earth in its existential “Great Filter” moment?

As enormous and old as the Universe is (90+ billion light years across, 14 billion years old), it seems likely that life, even intelligent life, must have evolved on billions of habitable planets.

But after extensive searching for evidence of extraterrestrial life for decades, we have yet to detect any signal from another advanced civilization. The question is why.

Some now speculate that extraterrestrial civilizations may actually not exist, due to a universal threshold horizon beyond which intelligent civilizations cannot survive — calling this “The Great Filter.”

Given the precipitous decline of human civilization on Earth today – nuclear weapons, climate change, overpopulation, resource depletion, species extinction, extremism, famine, disease, and disregard for science and truth – Earth may indeed be well into its own self-imposed, existential Great Filter at present.

Astronomers estimate that there may be between 100 billion and 400 billion stars just in our home Milky Way galaxy, and over 2 trillion galaxies across the observable Universe. So far, over 5,000 exoplanets (planets outside our solar system) have been discovered just in nearby space, and many are thought to be in habitable orbits (the “Goldilocks zone,” not too hot, not too cold).

As discussed by science writer Tim Urban, if 1% of stars in the Universe have habitable planets, and 1% of these develop life, and 1% of these living planets develop intelligent civilizations, then there should be perhaps 10 quadrillion (million-billion) intelligent civilizations in the Universe. In our galaxy alone, there would be as many as a billion Earth-like planets and 100,000 intelligent civilizations.

But given this astronomical probability of intelligent life in the Universe and even within our home galaxy, then, as physicist Enrico Fermi asked, “Where is everyone?” This has become known as “The Fermi Paradox.” Or, perhaps the better question, as others ask: “What happened to everyone?”

According to Urban, there are two categories of potential explanations to this cosmic question.

One is that technologically advanced alien civilizations are out there, but we remain unaware of them for a variety of reasons. Extraterrestrial civilizations may have visited Earth before humans were around to witness such (e.g., prior to 50,000 years ago); Earth is in a distant “rural” district of the galaxy not yet reached by advanced colonists; alien civilizations may be perfectly content where they are, and have no desire to reach out to explore across the galaxy and intergalactic space; intelligent civilizations may not wish to broadcast their presence and location due to the risk of hostile alien incursions; advanced civilizations are all quickly exterminated by other hostile alien civilizations; aliens are there and communicating, but we are unable to detect or interpret their signals; aliens are there, but are simply observing us without contact or interference (the “zoo hypothesis”); or that we are completely wrong about our reality and the Universe.

The other intriguing possible explanation for why we have had no contact with advanced extraterrestrial civilizations, is that there simply are none. It may be that there is a universal, cataclysmic threshold beyond which it is impossible for intelligent civilizations to continue to evolve — “The Great Filter.”

A Great Filter could include extraplanetary events such as extinction level asteroid impacts; massive gamma ray bursts; stars growing too hot and bright, ending life on orbiting planets (as is predicted for our sun a billion+ years from now); or self-imposed cataclysms such as exhausting life support systems of the planet (what we are now doing on Earth), climate change, or nuclear annihilation; or any/all of the above.

Some speculate (hope) that life on Earth has already passed its Great Filter horizon, and thus our technological civilization is simply rare or early in the evolution of the Universe, and will thus continue to advance. But another more worrying possibility is that we are in our Great Filter now, or it looms in our future. If so, this could mean that life across the Universe may have often evolved to our stage of technological development, but then hit an insurmountable threshold and vanishes.

This is clearly the most ominous scenario, as we, like other technological civilizations, would almost certainly not survive such an existential threshold.

It is clear that our current self-imposed environmental destruction on Earth is an existential Great Filter horizon. “Intelligent” civilization on Earth is currently in a tailspin, taking the biosphere down with it. There is still a path through our Great Filter to a sustainable future, but this path narrows every day.

Either we recognize and correct our self-destructive behavior soon, or we will surely become just another one of potentially billions of failed evolutionary experiments across the Universe, and vanish forever into the darkness of spacetime.

Rick Steiner is a retired University of Alaska environmental professor, founder of Oasis Earth, and author of Oasis Earth: Planet in Peril, available as a free download here: https://www.oasis-earth.com/oasis-earth-planet-in-peril