Friday, 2 May 2008

Fermi's Paradox

Nick Bostrom writes an interesting essay on anthropic observations, as usual. I agree with him that the answer to Fermi's "paradox" --- "why hasn't spacefaring life colonized our entire universe in ways we can detect" --- is that there isn't any.

But I think he misses a powerful argument that the "Great Barrier" to spacefaring life is the difficulties in our past, not the dangers in our future. It seems that if current progress continues, we're at most hundreds of years away from developing self-sustaining, space-capable artificial life --- AI, if you like --- even if we take the brute-force approach of brain simulation. It's hard to think of inevitable catastrophes that could wipe out all of a multitude of space-based intelligent machines with reproductive capability, even they were all confined to our solar system. Even if we don't make it to that point --- and I will not be surprised if we (or God) write an end to our history --- since we made it this far, given enough other civilizations one of them would be luckier and make it all the way, and go on to colonize the universe in observable ways.
But apparently they haven't.



13 comments:

  1. The universe is pretty big (estimates from Wikipedia figures suggest that our galaxy has a diameter of around 0.003% of the entire universe).
    I don't know what percentage of the universe is observable to us, but I'm going to go out on a limb here and suggest that it's somewhere between "limited" and "basically nothing".
    Drawing any conclusion based on what we can (or rather can't) currently observe seems somewhat bold. I can't detect the existence of any god (or gods), but I'm not going to dismiss the possibility based on what I can't see.

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  2. Well, I messed up that percentage with a typo in my calculation. Turns out it's more like 0.0001%.

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  3. Robert O'Callahan2 May 2008 06:22

    The thing is, if spacefaring, colonizing life emerges frequently in the universe, some of it should have emerged close enough to us, and long enough ago, to have expanded to be all around us, even right here in this solar system. Bostrom points out that 20M years is much more than enough time for a civilization emerging in our galaxy to occupy the whole thing. Give them another 200M years and we're in range of a lot of nearby galaxies.
    It's true our observations are consistent with all civilizations preferring not to expand and colonize --- just sitting in some hard-to-observe corner of the universe --- but that seems unrealistic. Bostrom covers that in his essay.

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  4. Well, I'm not quite as optimistic as you about the future... we have a few hurdles to overcome there too, resource issues and population pressures being the biggest (and these are in many ways closely related).
    That's not to say that one of the biggest hurdles we had to overcome was simply existing at all (I suspect technologically capable intelligence is a rather rare environmental adaptation), but that we're not "out of the woods" yet as it were.
    Still, an interesting article.

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  5. VanillaMozilla2 May 2008 17:37

    Since we can essentially observe next to nothing, it's awfully difficult to draw valid conclusions based on what we can observe. In fact, it's hard enough even to decide whether we can draw valid conclusions.
    The problem is that the universe is big. Really big. Communication is next to impossible. Colonization is completely speculative, or more realistically, in the realm of science fiction. This requires that you suspend disbelief: the notion of colonization requires amazing technology that somehow overcomes immense times and distances or somehow circumvents the laws of nature as we understand them. Could happen, I suppose. Or maybe not.
    You can postulate that somehow a few microbes get blasted into space on a meteor that wanders the universe and comes to rest on a hospitable planet--and that those microbes evolved into intelligent life. Could happen, I suppose, but maybe it didn't. Well, maybe organic molecules just form in interstellar space and evolve into intelligent life. Or maybe not. Maybe they'll find some intelligent moss under some icy rock on Mars. Or maybe not.
    I was sort of hoping they would find Sasquatch and the Yeti too, but so far, nothing. I just don't see how we'll ever know if there's anybody out there.

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  6. VanillaMozilla2 May 2008 18:07

    "Bostrom points out that 20M years is much more than enough time for a civilization emerging in our galaxy to occupy the whole thing."
    This remains to be proven. I doubt whether 20 M years is even enough time to occupy the nearest solar system. I'm not sure it's sufficient time even to travel to it.

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  7. Since you are a convinced Christian, don't you think that you are actually already in contact with extraterrestrial intelligent life? Granted, it's not exactly what Nick Bostrom is talking about, but that's not surprising considering how hard it is at any given point in time to predict the exact path a civilization will take from the current situation it is in.
    It has a lot to do with what man expects the future to be, which is directly influenced by the state of development he is in, another consequence of the anthropic principle. In other words, there could be another filter at work here: the one that makes it impossible for us to even think about something that's too far outside of what we have achieved so far.

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  8. Robert O'Callahan2 May 2008 23:31

    D Milne: like I said, I'm actually not all that optimistic about *our* future.
    VanillaMozilla: there's no reason interstellar travel should be hard for intelligent machines. Bostrom discusses that a bit. Reaching speeds of 0.01c is not hard. Travelling 100 light years --- a 10,000 year voyage --- is not a big deal, the machine can just sleep for as long as it takes.
    laszlo: interesting point.

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  9. I dunno. Taking an extremely conservative approach to the whole colonizing business, assuming 0.01 C as the average speed possible (thus 500 years average between stars), and being pessimistic about how many stars have colonizable/terraformable environments (set to 1%, meaning typically 10 LY between colonizable stars), a (live, not robotic) civilization that only moves on to colonizing a new world after an existing world is terraformed and stable (large supportive natural population that is reasonable to economize building another 1000-year colony ship), I can see it taking up to 4 trillion years just to colonize a single galaxy like ours.
    [Note: YMMV on the numbers; taking several very rough personal estimates.]
    Being slightly more aggressive (.1C travel, expansionist rather than colonist policies) could still take a few billion years.
    Of course that all assumes that there are never any issues which might set the civilization back (civil wars, change in political philosophies, etc), nor intrinsic limitations on perpetual growth (communication between the original world and the outliers becomes more and more difficult the larger the empire grows). Simply getting a civilization to invest in a project that won't even reach its starting point for 1000 years, never mind becoming usefully independent and able to provide a return on the investment to the original world, would be quite a challenge.
    If your only goal is to plant a flag on every single world in the galaxy to say "Kilroy was here!", sure, you could do that in a few tens of millions of years. But to equate that with the time it would take to grow a stable civilization seems a bit presumptuous.

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  10. Robert O'Callahan2 May 2008 23:38

    David, that assumes each colony only sends out one new colony so overall growth is only linear.
    What would really happen is that each colony can send out many new colonists --- expanding in all directions at once. Then the total time to colonize the entire galaxy depends mainly on the diameter of the galaxy. So even if it took 10,000 years to spread 10LY (that's very slow, 1000 years of 0.1c travel followed by a 9000 year holiday), we're talking less than 100M years to colonize the Milky Way.

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  11. Robert O'Callahan4 May 2008 07:04

    David, you seem to have missed the point about the colonizers being intelligent machines, not organic life.
    Machines don't need terraformed planets. They don't need planets at all, they can "live" just fine in space, collect solar power and get raw materials from asteroids, moons, etc. There are no obvious limits to their lifespan. They probably don't need to form large societies in order to be self-sustaining; it seems completely plausible that a single machine would be able to reproduce itself an unlimited number of times. They can power-off for long interstellar voyages, so these "colony ships" are not vast endeavours, just a machine mind and its robot agents attached to some propulsion device, plus some shielding and an alarm clock to wake it up on arrival.
    I agree that colonization of the galaxy by organic life as we know it is highly implausible, but that's not what we're talking about. (It's possible the machines might seed organic life as they go for some reason, e.g. if they were programmed to, but that's a different proposition.)

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  12. Robert O'Callahan4 May 2008 10:52

    Bostrom covers these arguments "maybe they don't like to expand", "maybe they don't like to build" in his essay, to some extent anyway.
    He points out that if just one out of all the AI civilizations in the galaxy is expansionist, it will expand throughout the galaxy. If just one of those likes to send signals of the type we could detect, our galaxy will be filled with such signals. If just one likes to build stellar-sized structures we could detect, we should be able to detect them.
    The alternative is that something makes all advanced civilizations non-expansionist and quiet, which would seem surprising, since life as we know it is ubiquitously neither. Even for a super-advanced civilization, internal and external competition would seem to favour the supremacy of expansionists.
    I suppose one remaining hypothesis is that the galaxy is dominated by a single super-civilization which chooses to remain quiet and hidden and suppresses all nascent competitor civilizations. For that to work, it would want to have probes in every solar system capable of developing life, ready to blow up that life before it switches to machine intelligence and becomes much harder to stop. Seems unlikely.

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  13. I've been thinking about Fermi too, and here's what I came up with:
    http://michaelgr.com/2008/05/09/virtual-reality-could-explain-the-fermi-paradox/
    I think it's a slightly different angle form what we usually see on the subject.

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