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Thread: What do you think is the most likely explanation for the Fermi paradox?

  1. #661
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    Quote Originally Posted by cosmocrazy View Post
    Its true we have only one example to work from and it maybe true that abiogenisis happened pretty quickly on Earth. But this does not mean that the same would be said for other worlds having similar initial conditions (1). If i'm correct in assuming that abiogenisis has not been achieved in the lab then there must have been a catalyst for it to appear when it did that we are not understanding. It could well be that this catalyst is the rare part (2). This aside, should abiogenisis be common place, should the "primordial soup" be a natural occurrence, with the right blend of chemicals and conditions, then this is still not evidence that technological life is eventually inevitable.

    For the purpose of this thread, our interest lies with life that can communicate one way or another across space. We have a multitude of magnificent aw-inspiring species of life on this planet, which is very encouraging and could quite possibly be very special. But as I stated, we (humans) are the only species to develop technology that enables us to go far beyond our evolutionary physical capabilities & limitations. We are able to use our planet's resources to build devices that can communicate through space, travel through space, visit other worlds... We can compare ourselves to other species of life on Earth, present and past, and yes we haven't got wings, super senses, 8 tentacles... but we have developed ways to overcome our physical and mental disadvantages. We have invented, designed and built machines and devices that are truly amazing. All this in a very short time frame relative to normal evolutionary stages and relative to the age of our planet.
    (1) Remember the Principle of Mediocrity again.

    (2) Well possibly the people who say the probability of life arising by chance are 1 in gazillions to the power of gazillions are actually correct. I've said this before, that although it could be extremely improbable, the probability is still greater than zero. It has a finite chance of happening. Hence the Strong Anthropic theory, which I find quite attractive. However there have been several papers debunking this idea. Anyhow, the logical position is that if it happened on Earth, and it happened quite quickly as well, that means it should be commonplace on Earth-like planets.

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    Quote Originally Posted by kzb View Post
    (1) Remember the Principle of Mediocrity again.

    (2) Well possibly the people who say the probability of life arising by chance are 1 in gazillions to the power of gazillions are actually correct. I've said this before, that although it could be extremely improbable, the probability is still greater than zero. It has a finite chance of happening. Hence the Strong Anthropic theory, which I find quite attractive. However there have been several papers debunking this idea. Anyhow, the logical position is that if it happened on Earth, and it happened quite quickly as well, that means it should be commonplace on Earth-like planets.
    Yes the principle of mediocrity stands to reason, but again is based on assumption rather than from evidence or rather a lack of since we have only one data source.

    I think this is the stance taken by most (my bold) and is good reason to look for worlds that may harbour liquid water, without argument a good place to start. I was just pointing out that, just maybe its not that simple.

    My stance is similar to your own and though I have my opinions on this subject those opinions are based on assumptions and gut feelings, so I try to remain open minded, considering all possibilities regardless of how improbable they might seem.

    I think the crux of this for me is, if we are alone, a fluke, unique... then what is the rest of the universe for? In other words, why are/would we be special?

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    Quote Originally Posted by cosmocrazy View Post
    Yes the principle of mediocrity stands to reason, but again is based on assumption rather than from evidence or rather a lack of since we have only one data source.

    I think this is the stance taken by most (my bold) and is good reason to look for worlds that may harbour liquid water, without argument a good place to start. I was just pointing out that, just maybe its not that simple.

    My stance is similar to your own and though I have my opinions on this subject those opinions are based on assumptions and gut feelings, so I try to remain open minded, considering all possibilities regardless of how improbable they might seem.

    I think the crux of this for me is, if we are alone, a fluke, unique... then what is the rest of the universe for? In other words, why are/would we be special?
    What is the rest of it for? It's the minimum necessary to evolve a conscious life form.

    Or, it is simply part of the simulation.

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    Quote Originally Posted by kzb View Post
    What is the rest of it for? It's the minimum necessary to evolve a conscious life form.
    .. and the evidence of earth-lifeforms is insufficient to evolve life elsewhere ..

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    Quote Originally Posted by kzb View Post
    (1) Remember the Principle of Mediocrity again.
    The "principle" of mediocrity is bunkum. It's on the order of God of the Gaps, IMO.
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

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    Quote Originally Posted by Noclevername View Post
    The "principle" of mediocrity is bunkum. It's on the order of God of the Gaps, IMO.
    It's not intrinsically bunkum.

    The mediocrity principle is the philosophical notion that "if an item is drawn at random from one of several sets or categories, it's likelier to come from the most numerous category than from any one of the less numerous categories".

    https://en.wikipedia.org/wiki/Mediocrity_principle

    It's not at all controversial purely from a statistical viewpoint.

    However, the evidence seems to show us that it is indeed broken at some point in the chain (or perhaps several points). The only way it is not broken is if there is something wrong with our assumptions about points on the chain.

    These could be wrong assumptions:

    1. The galaxy first became habitable billions of years ago

    2. Interstellar travel and communication is possible for at least some sufficiently advanced species

    3. At least some advanced species survive long-term.

    If any of these assumptions is false then the P of M is not broken.

    I actually prefer to believe the P of M is broken somewhere.

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    Was our item really drawn at random?

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    Quote Originally Posted by kzb View Post
    The mediocrity principle is the philosophical notion that "if an item is drawn at random from one of several sets or categories, it's likelier to come from the most numerous category than from any one of the less numerous categories".
    We have no numbers for most of the applicable categories. We don't know what's likely or unlikely. Again, drawing from an example of one is not statistics.
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    Quote Originally Posted by Noclevername View Post
    We have no numbers for most of the applicable categories. We don't know what's likely or unlikely. Again, drawing from an example of one is not statistics.
    Yes it is.

    The principle of mediocrity tells us there should be loads of advanced ETs out there. The fact that we have not detected any is what the paradox is all about.

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    Quote Originally Posted by Chuck View Post
    Was our item really drawn at random?
    I think the way it is explained in Wikipedia is not the best in this context.

    Say ETs range from non-expansive to very expansive. The expected distribution is approximately normal (Gaussian) around a mean value for expansiveness.

    If we dip our hand in a bucket containing all ET civilisations and pick one, that one is statistically more likely to come from close to the mean value for expansiveness than it is to come from one of the extremes.

    We ourselves are a sample of one drawn from that bucket. So we are more likely to be near average than extreme.

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    Quote Originally Posted by kzb View Post
    Yes it is.

    The principle of mediocrity tells us there should be loads of advanced ETs out there. The fact that we have not detected any is what the paradox is all about.
    You are simply incorrect. The principle of mediocrity is not a useful tool for analyzing a lack of data.
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

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    Quote Originally Posted by kzb View Post
    So we are more likely to be near average than extreme.
    More likely? If we had a distribution to look at, you could say that. We don't.
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

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    Quote Originally Posted by Noclevername View Post
    Another idea is that, having achieved interstellar travel and population control, hypothetical travelers could see no benefit to colonizing at all. Even if they are curious enough to go in person, it's conceivable that they would be just living on their own vessels and occasionally stopping at stars to restock, refuel and repair.
    Of all the Occam's Razors posted so far this one is sharp enough for me ;-)

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    Quote Originally Posted by kzb View Post
    I think the way it is explained in Wikipedia is not the best in this context.

    Say ETs range from non-expansive to very expansive. The expected distribution is approximately normal (Gaussian) around a mean value for expansiveness.

    If we dip our hand in a bucket containing all ET civilisations and pick one, that one is statistically more likely to come from close to the mean value for expansiveness than it is to come from one of the extremes.

    We ourselves are a sample of one drawn from that bucket. So we are more likely to be near average than extreme.
    It doesn't seem like we drew our planet at random. We picked one that we knew had expansive technological life. We'd have gotten the exact same result if we were the only such sample or the galaxy were full of them. I don't see how this tells us anything.

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    Quote Originally Posted by kzb View Post
    We ourselves are a sample of one drawn from that bucket. So we are more likely to be near average than extreme.
    Last I looked, we don’t have an immortal, highly expansive interstellar civilization. We have no examples at all of such a thing - a sample size of zero. All you’re doing is to speculate and declare your speculation to be established fact.

    The civilization we have now would be nearly undetectable by twin civilizations elsewhere in the galaxy.

    We simply have no way of saying what we will do in the future, nor do we have any reason to assume we can say what other species would do, if they exist.

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    Quote Originally Posted by Van Rijn View Post
    The civilization we have now would be nearly undetectable by twin civilizations elsewhere in the galaxy.
    Or even from our nearest stellar neighbors: https://archive.briankoberlein.com/2...ome/index.html

    They'd probably need to be deliberately sending a very strong, directional signal. Broadcast would spread out and weaken quickly (inverse square law), whereas a highly collimated signal such as a laser could maintain some degree of coherency over a much greater distance. And the message would have to be long enough and clear enough to distinguish it from background noise.
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    Quote Originally Posted by Noclevername View Post
    Or even from our nearest stellar neighbors: https://archive.briankoberlein.com/2...ome/index.html

    They'd probably need to be deliberately sending a very strong, directional signal. Broadcast would spread out and weaken quickly (inverse square law), whereas a highly collimated signal such as a laser could maintain some degree of coherency over a much greater distance. And the message would have to be long enough and clear enough to distinguish it from background noise.
    Still theoretically possible (even if its practicality is considered doubtful).

    The real issue lies in the truth value of the initially posited assumption of: 'a bucket containing all ET civilisations'. Any logical thought experiment following that assumption can only at best, ever return that same truth value, because science has no objective evidence for supporting any of that, (or not supporting any of that).

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    Quote Originally Posted by Van Rijn View Post
    Last I looked, we don’t have an immortal, highly expansive interstellar civilization. We have no examples at all of such a thing - a sample size of zero. All you’re doing is to speculate and declare your speculation to be established fact.

    The civilization we have now would be nearly undetectable by twin civilizations elsewhere in the galaxy.

    We simply have no way of saying what we will do in the future, nor do we have any reason to assume we can say what other species would do, if they exist.
    Expansiveness, I thought of as a characteristic of a species, that is all. It could've been any characteristic, size, weight, number of limbs etc.

    The fact there is not an already-existing immortal highly expansive interstellar civilisation IS the paradox. That actually IS the question, not why don't we detect radio signals. As others have said, radio technology is probably a short lived phase in a subset of ET species at best.

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    Quote Originally Posted by Selfsim View Post
    Still theoretically possible (even if its practicality is considered doubtful).

    The real issue lies in the truth value of the initially posited assumption of: 'a bucket containing all ET civilisations'. Any logical thought experiment following that assumption can only at best, ever return that same truth value, because science has no objective evidence for supporting any of that, (or not supporting any of that).
    The lucky-dip experiment on the principle of mediocrity follows on from statistics and probability theory, it is better than objective evidence, it is from first principles.

    Actually no-one has picked out the real hole in the argument, and that is we are 99%+ percentile on every factor. After all, in a large enough population of habitable planets, one or two WILL shake a six time after time.

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    Is immortality of one civilization required?

    Empires and comparable large organizations rise and fall. A civilization or comparable society might spread their members to various nearby star systems, and then the originating societies may collapse, break apart or fall into lesser unbound communities. As long as there are survivors in the colonies, new cultures can arise to repeat the cycle, possibly including establishing their own interstellar colonies further out or in other directions. And this cycle, while much slower than the maximum rate of spread, could still result in a large number of inhabited systems.

    The interstellar colonies would likely not be tightly bound to their originators in any case, due to distance, light lag, and the implausibility of enforcement.
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    Quote Originally Posted by Noclevername View Post
    Is immortality of one civilization required?

    Empires and comparable large organizations rise and fall. A civilization or comparable society might spread their members to various nearby star systems, and then the originating societies may collapse, break apart or fall into lesser unbound communities. As long as there are survivors in the colonies, new cultures can arise to repeat the cycle, possibly including establishing their own interstellar colonies further out or in other directions. And this cycle, while much slower than the maximum rate of spread, could still result in a large number of inhabited systems.

    The interstellar colonies would likely not be tightly bound to their originators in any case, due to distance, light lag, and the implausibility of enforcement.
    For the purposes of this discussion, what is meant is, immortality of one species or descendants of that species. Civilisations on different planets originating from the same seed ET civilisation could be highly differentiated as you say, but they still count as belonging to that original ET.

    Imagine if humans spread throughout a 1kpc radius of the solar system. At that distance there could be no effective influence of Earth on the colony planets. At some point in the future Earth could get destroyed. But that does not mean that other inhabited worlds in that 1kpc radius wouldn't count as human worlds.

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    Quote Originally Posted by kzb View Post
    The lucky-dip experiment on the principle of mediocrity follows on from statistics and probability theory, it is better than objective evidence, it is from first principles.
    Nope. Your usage of it, is flawed by circular logic.

    As has been pointed out several times now, there is no objective evidence that 'Earth-life' is a subset of any 'ET civilisations' in your bucket. In your thought experiment, you have assumed that it is, and then used quite valid statistical principles to uphold your belief (or truth) that it is. If nothing at all is known about this, then the Principle of Indifference applies and the only thing in your bucket is either earth-life, or nothing .. which may then be why you then concluded(?):
    Quote Originally Posted by kzb
    ... we are 99%+ percentile on every factor.
    However, you then introduce other factors such as 'habitable planets', which is once again, only demonstrated to correlate with earth-life (and still no evidence to establish correlation with 'ET civilisations' .. in fact, none of our solar system habitable planets is looking too promising as a candidates for space-faring 'ET civilisations' either):
    Quote Originally Posted by kzb
    After all, in a large enough population of habitable planets, one or two WILL shake a six time after time.
    Abiogenesis (pre-biotic chemistry) is currently understood as being dissimilar from a purely random process, so the relevance of 'shaking' anything has its problems here.

    Also, using the term 'habitable' as justification, is a simple reversal of the Mediocrity Principle and looks as though it is now claimed that the habitability characteristic of Earth, determines the dominating characteristic of the bucket population, rather than the other way around(?)

    (Not that any of these issues separate your argument from all the other ET civilisation arguments thus far presented ... but it needs to be shown that using philosophical tenets, followed by purely statistical arguments adds no weight, and turns out as being fallacious).

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    Quote Originally Posted by Selfsim View Post
    Nope. Your usage of it, is flawed by circular logic.

    As has been pointed out several times now, there is no objective evidence that 'Earth-life' is a subset of any 'ET civilisations' in your bucket. (1) In your thought experiment, you have assumed that it is, and then used quite valid statistical principles to uphold your belief (or truth) that it is. If nothing at all is known about this, then the Principle of Indifference applies and the only thing in your bucket is either earth-life, or nothing .. which may then be why you then concluded(?):

    However, you then introduce other factors such as 'habitable planets', which is once again, only demonstrated to correlate with earth-life (2) (and still no evidence to establish correlation with 'ET civilisations' .. in fact, none of our solar system habitable planets is looking too promising as a candidates for space-faring 'ET civilisations' either) (3):
    Abiogenesis (pre-biotic chemistry) is currently understood as being dissimilar from a purely random process, so the relevance of 'shaking' anything has its problems here (4).

    Also, using the term 'habitable' as justification, is a simple reversal of the Mediocrity Principle and looks as though it is now claimed that the habitability characteristic of Earth, determines the dominating characteristic of the bucket population, rather than the other way around(?) (2)

    (Not that any of these issues separate your argument from all the other ET civilisation arguments thus far presented ... but it needs to be shown that using philosophical tenets, followed by purely statistical arguments adds no weight, and turns out as being fallacious).
    (1) No there is no direct proof, and in the absence of that, the best we can do is the principle of mediocrity. There's nothing unreasonable about that.

    (2) It could be extended to include planets suitable for non-earth like life if you want, it does not adversely affect the argument. In fact it helps it, because it would mean there are far more "habitable" planets.

    (3) That would be the rare-Earth hypothesis, which I respect. On the other hand a paper a couple of years ago predicted 1.1 habitable planets per G-class star, on average.

    (4) Abiogenesis either happens or it doesn't. It's heads or tails during the useful life of the planet. Or it could be likened to the probability of throwing a 6. Most things I read imply that it's highly likely to happen, like throwing a 6 with a very loaded die.

    I never concluded we are 99th percentile on every factor. Just pointing out it is possible as an explanation of the paradox:

    Let's imagine there are just five stages in evolving an intelligent species, and each stage has a probability of success of 1-in-6. That is like throwing 5 dice and expecting five sixes. The chance of that happening is 1 in 7776. But then imagine there have been 7776 Earth-like planets produced in the history of the galaxy up to the present day. Our expectation value for the number of intelligent races is then 1.00 -and here we are. So it does conceivably work, but it is statistically improbable.

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    Quote Originally Posted by kzb View Post
    (1) No there is no direct proof, and in the absence of that, the best we can do is the principle of mediocrity. There's nothing unreasonable about that.
    Again and again it's been pointed out that it is not the best measure, and that you are giving undue weight to a shaky and misapplied premise.

    From here out I'll say nothing further about the POM.
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

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    Again, I read a argument in a SETI book, based on Bayesian math (which I never took, so I did not bother looking up the reference) that if there are N steps to a technological civilization, and they all normally take much longer than the lifespan of the universe to complete, BUT you "force" all of them to occur (because we have an existence proof), then the intervals between them, during the "window" when such a species is able to evolve, is equal to window/(N+1). This is true even if one of the steps is astronomically longer than the others.
    The book argued from this that life originated on Mars, since Mars solidified and became habitable earlier than Earth did, and was transfered to Earth by lithopanspermia, to account for the "premature" development of life here.
    SHARKS (crossed out) MONGEESE (sic) WITH FRICKIN' LASER BEAMS ATTACHED TO THEIR HEADS

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    Quote Originally Posted by Noclevername View Post
    Again and again it's been pointed out that it is not the best measure, and that you are giving undue weight to a shaky and misapplied premise.

    From here out I'll say nothing further about the POM.
    Well you are going against the mainstream literature in this field by taking that position.

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    Quote Originally Posted by Tom Mazanec View Post
    Again, I read a argument in a SETI book, based on Bayesian math (which I never took, so I did not bother looking up the reference) that if there are N steps to a technological civilization, and they all normally take much longer than the lifespan of the universe to complete, BUT you "force" all of them to occur (because we have an existence proof), then the intervals between them, during the "window" when such a species is able to evolve, is equal to window/(N+1). This is true even if one of the steps is astronomically longer than the others.
    The book argued from this that life originated on Mars, since Mars solidified and became habitable earlier than Earth did, and was transfered to Earth by lithopanspermia, to account for the "premature" development of life here.
    That maths sounds reasonable and (I think) says what I was trying to say a few posts back. That is, if one stage takes a lot longer than average, statistically the next stages should compensate for that, so the total time is closer to average.

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    Quote Originally Posted by kzb View Post
    Well you are going against the mainstream literature in this field by taking that position.
    What mainstream? It’s all speculation at this point, which is why people argue and reargue their own preferred chains of speculation.

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    Quote Originally Posted by Van Rijn View Post
    What mainstream? It’s all speculation at this point, which is why people argue and reargue their own preferred chains of speculation.
    The principle of mediocrity is well entrenched in this field. Without it there is nothing much to go on.

    Also it is the very basis of the paradox. If you believe that we are a special, one-off event, there is no paradox.

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    IIRC there were six events in the book:
    Abiogenesis
    Photosynthesis
    Sexual Reproduction
    Eukaryotes
    Metazoa
    Sapience of a prehensile species
    This divides the habitable lifespan into seven equal periods.
    Each period was about 700 million years long, so life should have begun about 4.2 billion years ago at least.
    SHARKS (crossed out) MONGEESE (sic) WITH FRICKIN' LASER BEAMS ATTACHED TO THEIR HEADS

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