The Great Filter theory suggests humans have already conquered the threat of extinction
2012-12-21 0:00

By George Dvorsky | io9.com





Itís difficult to not be pessimistic when considering humanityís future prospects. Many people would agree that itís more likely than not that weíll eventually do ourselves in. And in fact, some astrobiologists theorize that all advanced civilizations hit the same insurmountable developmental wall we have. They call it the Great Filter. Itís a notion thatís often invoked to explain why weíve never been visited by extraterrestrials.

But there is another possible reason for the celestial silence. Yes, the Great Filter exists, but weíve already passed it. Hereís what this would mean.

Before we can get to the Great Filter hypothesis we have to appreciate what the Fermi Paradox is telling us.

The Fermi Paradox and the Great Silence

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 ó but this hypothesis seems inconsistent with the lack of observational evidence to support it.

Despite much of what popular culture and sci-fi would lead us to believe, the fact that we havenít been visited by ETIs is disturbing. Our galaxy is so ancient that it could have been colonized hundreds, if not thousands, of times over by now. Even the most conservative estimates show that we should have already made contact either directly or indirectly (such as from dormant Bracewell communication probes).

Some skeptics dismiss the Fermi Paradox by suggesting that ETIís have come and gone, or that they wouldnít find us interesting.

Unfortunately, most solutions to the FP donít hold for a number of reasons, including the realization that a colonization wave of superintelligent aliens would likely rework the fabric of all life in the cosmos (e.g. uplifting), or that these solutions are sociological in nature (i.e. they lack scientific rigor and donít necessarily apply to the actions of all advanced civilizations; all it would take is just one to think and behave differently ó what astrobiologists refer to as the non-exclusivity problem).

There have been many attempts to resolve the Fermi Paradox, including the herculean attempt by Stephen Webb in his book, Fifty Solutions to Fermiís Paradox and the Problem of Extraterrestrial Life.

But one solution stands out from the others, mostly on account of its brute elegance: The Great Filter.

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 ó 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.

Many look upon the GF as evidence that weíll destroy ourselves in the future. 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. Weíre not even close to going interstellar, yet weíre certainly capable of self-annihilation.

But that doesnít mean this interpretation of the GF is the correct one. Rather, itís quite possible that human civilization has already passed the Great Filter. Should this be the case, it would be exceptionally good news. Assuming thereís no other filter awaiting us in the future, it means we might be the first and only intelligent civilization in the Milky Way.

Itís a possibility, however, that demands explanation. If the filter is behind us, what was it? And how did we manage to get past it? Interestingly, there are some excellent candidates.

Rare Earth

First and foremost thereís the Rare Earth Hypothesis (REH), the suggestion that the emergence of life was extremely improbable for a confluence of reasons. The theory essentially suggests that we hit the jackpot here on Earth.

This argument, which was first articulated by geologist Peter Ward and astrobiologist Donald E. Brownlee, turns the whole Copernican Principle on its head. Instead of saying that weíre nothing special or unique, the REH implies the exact opposite ó that we are freakishly special and unique. What we see here on Earth in this solar system and in this part of the Galaxy may be a remarkable convergence of highly unlikely factors ó factors that have resulted in a perfect storm of conditions suitable for the emergence of complex life.

Itís important to note that Ward and Brownlee are not implying that itís one or two conditions that can explain habitability, but rather an entire array of happy accidents. For example, stars might have to be of the right kind (including adequate metallicity and safe distance from dangerous celestial objects), and planets must be in a stable orbit with a large moon. Other factors include the presence of gas giants, plate tectonics, and many others.



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Read the full article at: io9.com











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