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The Great Filter
2008-Sep-23, Tuesday 14:29
So, playing Spore, with its enormous number of interstellar civilizations, had me thinking lately about the so-called "Great Filter" (also known as the Fermi Paradox).
For those who don't want to read, the basic summary is this--there are billions of stars in the galaxy. Even if less than 1% of 1% of those are capable of supporting sentient life, that's still thousands of intelligent civilizations. Assuming they achieve relativistic travel, a single civilization could expand to colonize and terraform every planet in the galaxy in only a few million years--and much, much faster than that if FTL travel is possible. The only thing that could stop them, after they got large enough, would be another civilization of similar expanse. So why haven't we found any hard evidence of aliens yet, either in their visiting Earth or in hearing communications? The basic possibilities come down to this:
A) Because there aren't any. Intelligent life is far rarer than we expect...or something destroys nascent civilizations before they expand too far. This (well, and the Borg) seems to be the inspiration for Spore's Grox.
B) Intelligent life destroys itself before advancing. Whether in ecological catastrophy, planetary war, or a similar armageddon. The problem here is that once a civilization expands beyond a handful of planets it would take an enormous catastrophy to destroy it.
C) Technical problems in discovery or communication. SETI mostly listens for radio signals, and human civilization now is slowly moving past wide-spread use of radio signals. Less than a century of easily-detectable transmissions make it extremely hard for any civilization to discover another one. There's also the aliens among us hypothesis, which is that they're already here but keeping themselves hidden, or the posthuman hypothesis, which is that alien civilizations would go through a technological singularity and become essentially impossible for humans to meaningfully communicate with, even if we could find them.
D) The universe is expensive to colonize. Another possibility is alien races who do not have the urge to expand, though this becomes less tenable when projected over extremely long time scales. This also gets into things like cosmological constants being different in different places and other things we have little or no evidence for.
So, what do you think? Are they out there, and if so, where are they?
For those who don't want to read, the basic summary is this--there are billions of stars in the galaxy. Even if less than 1% of 1% of those are capable of supporting sentient life, that's still thousands of intelligent civilizations. Assuming they achieve relativistic travel, a single civilization could expand to colonize and terraform every planet in the galaxy in only a few million years--and much, much faster than that if FTL travel is possible. The only thing that could stop them, after they got large enough, would be another civilization of similar expanse. So why haven't we found any hard evidence of aliens yet, either in their visiting Earth or in hearing communications? The basic possibilities come down to this:
A) Because there aren't any. Intelligent life is far rarer than we expect...or something destroys nascent civilizations before they expand too far. This (well, and the Borg) seems to be the inspiration for Spore's Grox.
B) Intelligent life destroys itself before advancing. Whether in ecological catastrophy, planetary war, or a similar armageddon. The problem here is that once a civilization expands beyond a handful of planets it would take an enormous catastrophy to destroy it.
C) Technical problems in discovery or communication. SETI mostly listens for radio signals, and human civilization now is slowly moving past wide-spread use of radio signals. Less than a century of easily-detectable transmissions make it extremely hard for any civilization to discover another one. There's also the aliens among us hypothesis, which is that they're already here but keeping themselves hidden, or the posthuman hypothesis, which is that alien civilizations would go through a technological singularity and become essentially impossible for humans to meaningfully communicate with, even if we could find them.
D) The universe is expensive to colonize. Another possibility is alien races who do not have the urge to expand, though this becomes less tenable when projected over extremely long time scales. This also gets into things like cosmological constants being different in different places and other things we have little or no evidence for.
So, what do you think? Are they out there, and if so, where are they?
