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23 September 2008 @ 02:29 pm
The Great Filter  
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?
Current Mood: thoughtfulthoughtful
Current Music: Chronotrigger - People Without a Hope
Adrian Forestdalziel_86 on September 23rd, 2008 09:38 am (UTC)
From a post-structuralist perspective, my favourite solutions to the Fermi paradox are variants on the idea that there's an incompatibility in communication. The Wikipedia article you linked to touches on some of these variants, most of which focus on the idea that aliens are communicating in ways we can't perceive.
Jaideraijaiderai on September 23rd, 2008 10:23 am (UTC)
Another possibility is that the aliens are there, know about the Earth, and have decided to have nothing to do with us.

The search is for intelligent life, remember. We have been rejected. ;)
dorchadas: Great Old Onesdorchadas on September 23rd, 2008 01:01 pm (UTC)
The "Zoo hypothesis." Only problem with that is it assumes we're special. :-p
Joelkraada on September 23rd, 2008 02:02 pm (UTC)
Not necessarily; all that needs to happen is that they think life is special and worth preserving no matter how it evolves.

The obvious exception of course is if that life tries to kill them, but once you're sufficiently advanced and the life you're watching starts to creep out into the universe you can come down and explain how they need to be good with your Very Big Guns and most nascent civilizations should comply for the most part . . .
dorchadasdorchadas on September 23rd, 2008 03:51 pm (UTC)
If they're anything like most human civilizations, they'll comply as long as it's useful and then unleash the backstabbing as soon as its convenient. Then again, who knows how alien psychologies would work?

It also would require a specific set of factors, like an ur-civilization that acts as a peacekeeper to keep non-interstellar capable races from being contacted, and/or is the only civilization around.
Matt Lindquistgreenblackevil on September 23rd, 2008 04:29 pm (UTC)
Oh they're out there. I watched way too much star trek as a young'un to believe anything else. I do, however, believe that not all sentient life becomes technologically advanced, and that not all technologically advanced life forms can communicate with each other. Think about it another way, too. If a sentient life form is millions of years ahead of us in evolution, they would be to us what we are to baboons- totally incomprehensible. So for all we know, they have been by us, passed by, or just didn't register with us.
(Deleted comment)
Jnytesenvy on September 24th, 2008 03:03 am (UTC)
i think that because i am a believer in evolution in general that the universe is vastly too big of a space for us to be alone. it would really be way too much like god's own garden of eden if we were alone.
q99q99 on September 25th, 2008 08:43 am (UTC)
I like C... life cropped up pretty fast on Earth, and conditions like that aren't *that* rare.

Alternatively, life may be common, intelligence combined with tooluse may be the crapshoot.