100 Billion planets in the Milky Way Galaxy, and not one signal from another advanced civilization?
In The Great Filter theory suggests humans have already conquered the ... George Dvorsky recounts the Fermi Paradox.
The so-called "Great Silence" is the contradictory and counter-intuitive observation that we have yet to see any evidence for the existence of aliens. The size and age of the Universe suggests that many technologically advanced extraterrestrial intelligences (ETIs) ought to exist — but this hypothesis seems inconsistent with the lack of observational evidence to support it. [emphasis mine]
Why haven't we seen evidence of other advanced civilizations?
But one solution stands out from the others, mostly on account of its brute elegance: The Great Filter.
Conceived in 1998 by Robin Hanson, the GF is the disturbing suggestion that there is some kind of absurdly difficult step in the evolution of life — one that precludes it from becoming interstellar.
And like the immutable laws of the universe, the GF is a stumbling block that holds true across the board; if it applies here on Earth, it applies everywhere.
The basic idea is that every civilization destroys itself before developing space-faring technologies. Hence the empty cosmos. Given our own trajectory and the ominous presence of apocalyptic weapons, this scenario certainly seems plausible. We're not even close to going interstellar, yet we're certainly capable of self-annihilation. [emphasis mine]
Our climate crisis is the obvious candidate for The Great Filter. Any species which coevolved with fire mastery, such as ours, would automatically find itself in the same situation. Fossil fuel use would be an irresistible energy source.
It comes down to alternation between aerobic and anaerobic planetary ocean chemistry. Fossil fuels are primarily formed during long periods in which an anoxic ocean prevents decay of falling organic material. Hydrocarbon molecules store carbon removed from the atmosphere along with energy. Through tens of thousands of years, the planet recovers from excess atmospheric carbon which caused the over heating, which caused the anoxic ocean, by accumulating energy and carbon rich ocean sediments.
This is a recent understanding. This picture was only pieced together during the last three decades. The handful of known and suspected anoxic events have been tied geologically to large-scale production of the world's oil reserves in worldwide bands of black shale in the geologic record. Likewise the high relative temperatures believed linked to so called "super-greenhouse events"[6
Most of our fossil fuel was produced this way as Earth recovered from the end Permian Extinction.
Since accumulation of carbon dioxide from burning fossil fuel isn't noticeable to unaided senses, it makes sense that the danger of changing planetary chemistry would be invisible to rising civilizations, until it's too late. By returning carbon scrubbed out over tens of thousands of years within a few centuries, other fire-dependent civilizations super-accelerated a push toward aerobic planetary chemistry.
As I see it most advanced alien civilizations would have faced the same challenge we face now. Pumping the carbon from their fossil fuels back into their atmospheres they created a runaway greenhouse effect, causing their own extinction. Given the lack of evidence for their survival, this filter is an extraordinary challenge to which few species rise.
I hope we prove to be extraordinary, and use the information at hand to avert a similar fate.