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

  1. #631
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    Quote Originally Posted by Noclevername View Post
    OK, say you're right. Intelligent life existed long ago, for the sake of this argument. That still leaves ALL the other obstacles I listed. Any ONE of which equals a no-show.
    All the ones you listed plus many more besides !

    So your explanation is that intelligent life is not very rare, but:

    it either does not last much beyond our stage of technology, or they (or their AI descendants) never leave their home system.

    Also they do not make any observable mark or signal of their civilisation, although they are billions of years old.

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    Quote Originally Posted by kzb View Post
    Theories also say that all the steps from the beginning of life to humans were almost inevitable.
    This is the one that I think is most likely wrong. That is, I think it most likely that there is a bottleneck behind us (which still leaves open the possibility of a bottleneck ahead of us, too). My basis for thinking this is looking at the time scales for development. Life appears to have formed on Earth quite early, almost as soon (a few hundred million years, fairly brief in geological time scales) as the Earth became sufficiently hospitable to life. But then there's a much longer gap of 2 or 3 billion years when life seemed content to remain single prokaryotic cells. It seems like the jump to eukaryotes and then the jump to multicellular life do not appear to be almost inevitable. And then another billion and a half years before you get to us. My speculation, based on admittedly few data points, is that if we someday survey other star systems for life, we'll find life roughly equivalent to our single celled organisms on most worlds with reasonably hospitable temperatures and liquid water, but that more complex life will be significantly less common, and intelligent life may turn out to be vanishingly rare. I think discovering other intelligent life in the universe would be one of the most exciting discoveries ever, but it doesn't seem implausible that it might not be there to find.
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    Quote Originally Posted by kzb View Post
    All the ones you listed plus many more besides !

    So your explanation is that intelligent life is not very rare, but:

    it either does not last much beyond our stage of technology, or they (or their AI descendants) never leave their home system.

    Also they do not make any observable mark or signal of their civilisation, although they are billions of years old.
    No, "it's rare" is one of the obstacles.
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    Quote Originally Posted by Grey View Post
    This is the one that I think is most likely wrong. That is, I think it most likely that there is a bottleneck behind us (which still leaves open the possibility of a bottleneck ahead of us, too). My basis for thinking this is looking at the time scales for development. Life appears to have formed on Earth quite early, almost as soon (a few hundred million years, fairly brief in geological time scales) as the Earth became sufficiently hospitable to life. But then there's a much longer gap of 2 or 3 billion years when life seemed content to remain single prokaryotic cells. It seems like the jump to eukaryotes and then the jump to multicellular life do not appear to be almost inevitable. And then another billion and a half years before you get to us. My speculation, based on admittedly few data points, is that if we someday survey other star systems for life, we'll find life roughly equivalent to our single celled organisms on most worlds with reasonably hospitable temperatures and liquid water, but that more complex life will be significantly less common, and intelligent life may turn out to be vanishingly rare. I think discovering other intelligent life in the universe would be one of the most exciting discoveries ever, but it doesn't seem implausible that it might not be there to find.
    I share your view,
    Its all very speculative, and since we have only one example (Earth) then our data is very limited. But, as you pointed out, if we look at the data on how humans developed then its rather astonishing we ever developed at all.

  5. #635
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    Quote Originally Posted by Noclevername View Post
    No, "it's rare" is one of the obstacles.
    Yes but that is not what they are saying. I was replying to those who say ET could be commonplace, but we just don't detect them.

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    Quote Originally Posted by Grey View Post
    This is the one that I think is most likely wrong. That is, I think it most likely that there is a bottleneck behind us (which still leaves open the possibility of a bottleneck ahead of us, too). My basis for thinking this is looking at the time scales for development. Life appears to have formed on Earth quite early, almost as soon (a few hundred million years, fairly brief in geological time scales) as the Earth became sufficiently hospitable to life. But then there's a much longer gap of 2 or 3 billion years when life seemed content to remain single prokaryotic cells*. It seems like the jump to eukaryotes and then the jump to multicellular life do not appear to be almost inevitable. And then another billion and a half years before you get to us. My speculation, based on admittedly few data points, is that if we someday survey other star systems for life, we'll find life roughly equivalent to our single celled organisms on most worlds with reasonably hospitable temperatures and liquid water, but that more complex life will be significantly less common, and intelligent life may turn out to be vanishingly rare. I think discovering other intelligent life in the universe would be one of the most exciting discoveries ever, but it doesn't seem implausible that it might not be there to find.
    The chain of reasoning IS broken somewhere, but that is what the Fermi paradox is all about !

    * The long gap between prokaryotes and complex life was cited by no less than Brian Cox on his TV programme. This 2-3 billion year gap implies that particular step in evolution is statistically unlikely to occur. However, on previous threads, I think it was Colin Robinson who shot it down.

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    Quote Originally Posted by cosmocrazy View Post
    I share your view,
    Its all very speculative, and since we have only one example (Earth) then our data is very limited. But, as you pointed out, if we look at the data on how humans developed then its rather astonishing we ever developed at all.
    We've had this before though. A few years ago I took this view as well, i.e the dinosaurs ruled the world no problem for 160 million years, with brains the size of walnuts.

    But then people point out that the dinosaurs were getting cleverer before they got wiped out. The arrow of evolution is always towards more brain power.

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    Quote Originally Posted by cosmocrazy View Post
    I share your view,
    Its all very speculative, and since we have only one example (Earth) then our data is very limited. But, as you pointed out, if we look at the data on how humans developed then its rather astonishing we ever developed at all.
    Absolutely. It's worth pointing out that our own development was preceded by 5 major mass extinction events and numerous smaller ones. Each of which had differing causes and each of which necessarily had to happen such that the ecological voids created by these disasters allowed evolution to shape the biosphere of the planet to properly accommodate us. This is almost treading on determinism or even a sort-of 'fine tuning' argument but is nevertheless a matter of fact.

    Quote Originally Posted by kzb View Post
    The arrow of evolution is always towards more brain power.
    This is really only true if and only if there is an evolutionary impetus for such things. I don't consider, for example, ants or honey bees smart or clever despite their complex colony building and eusocial living arrangements. There are many families of organisms that have had very long time frames to develop, but only a very small handful really fit your point.
    Last edited by deadie148; 2020-Jan-10 at 11:42 AM.

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    Quote Originally Posted by kzb View Post
    Yes but that is not what they are saying. I was replying to those who say ET could be commonplace, but we just don't detect them.

    Well, to them I'd say that so far in our investigations, the stable conditions we've determined necessary for evolution of complex life have been seeming less and less common than we once thought, and the more we find out, the more difficulties we discover. So while life may be (relative to the scale of the Universe) common, it's probably going to be a puddle of ocean floor slime rather than an intelligent starfaring being.
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    Quote Originally Posted by kzb View Post
    Yes but that is not what they are saying. I was replying to those who say ET could be commonplace, but we just don't detect them.
    We could set a rough upper limit by considering what appears to be technically feasible. Deliberate interstellar communication would be feasible with current technology - it doesn’t require assumptions about additional technological development or feasibility. Humans haven’t tried very hard to send signals out to interstellar space, and in fact some argue against it. But, if technological ETs developed in most star systems, that would raise a good possibility that enough would try transmitting that we could have detected at least one by now. Of course, we still could miss them if civilization lifetime is typically short, but it does suggest we could put an upper limit as something significantly below the number of long lived stars in the galaxy.

    I would tend to suspect they would be rare, if any at all exist, but I am more interested in what boundaries can be placed on the issue.

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    Quote Originally Posted by kzb View Post
    OK, but tell us WHY?

    Theories say that there were Earth-like planets 8 billion years ago.

    Theories also say that all the steps from the beginning of life to humans were almost inevitable.

    So if we are the first, what is wrong with these theories? This is what we have to explain.
    I suspect it is getting TO the beginning of life that is the problem.
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    Quote Originally Posted by kzb View Post
    The arrow of evolution is always towards more brain power.
    In one branch of one line of Earth's evolutionary paths. Trees are not getting smarter. Jellyfish are as old as man and they have no brains.
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

  13. #643
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    Quote Originally Posted by Noclevername View Post
    Trees are not getting smarter.
    That's what you think.
    As above, so below

  14. #644
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    Quote Originally Posted by Grey View Post
    This is the one that I think is most likely wrong. That is, I think it most likely that there is a bottleneck behind us (which still leaves open the possibility of a bottleneck ahead of us, too). My basis for thinking this is looking at the time scales for development. Life appears to have formed on Earth quite early, almost as soon (a few hundred million years, fairly brief in geological time scales) as the Earth became sufficiently hospitable to life. But then there's a much longer gap of 2 or 3 billion years when life seemed content to remain single prokaryotic cells. It seems like the jump to eukaryotes and then the jump to multicellular life do not appear to be almost inevitable. And then another billion and a half years before you get to us. My speculation, based on admittedly few data points, is that if we someday survey other star systems for life, we'll find life roughly equivalent to our single celled organisms on most worlds with reasonably hospitable temperatures and liquid water, but that more complex life will be significantly less common, and intelligent life may turn out to be vanishingly rare. I think discovering other intelligent life in the universe would be one of the most exciting discoveries ever, but it doesn't seem implausible that it might not be there to find.
    My own explanation is similar to yours, except that I think the chances of two intelligent civilizations existing within a reasonable distance to each other (say < 100 ly), and at the same time, are quite low.
    “Of all the sciences cultivated by mankind, Astronomy is acknowledged to be, and undoubtedly is, the most sublime, the most interesting, and the most useful. For, by knowledge derived from this science, not only the bulk of the Earth is discovered, but our very faculties are enlarged with the grandeur of the ideas it conveys, our minds exalted above their low contracted prejudices.” - James Ferguson

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    Quote Originally Posted by Fiery Phoenix View Post
    My own explanation is similar to yours, except that I think the chances of two intelligent civilizations existing within a reasonable distance to each other (say < 100 ly), and at the same time, are quite low.
    Yep, and it appears technological life could be a very rare occurrence, so based on this premise, the odds of 2 species with similar development co existing within such a small area (relative to the galaxy let alone the universe) at the same time would be extremely low.

    Unless of course panspermia had somehow taken place and a few suitable close by environments had enabled similar evolution to develop. But for life to spontaneously develop and evolve to technology status, so close, could be extremely rare.

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    Quote Originally Posted by Tom Mazanec View Post
    I suspect it is getting TO the beginning of life that is the problem.
    Sometime I think that as well. But then I read something about all the chemicals of life being present all over the place and I change my mind again.

    It's just a suspicion. Really what we are after is proof or at least some strong objective evidence to back up the assertion. Otherwise it isn't science surely.

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    Quote Originally Posted by Noclevername View Post
    In one branch of one line of Earth's evolutionary paths. Trees are not getting smarter. Jellyfish are as old as man and they have no brains.
    Reptiles are smarter than amphibians. Mammals are smarter than reptiles. Octopus are smarter than jellyfish.

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    Quote Originally Posted by kzb View Post
    Sometime I think that as well. But then I read something about all the chemicals of life being present all over the place and I change my mind again.

    It's just a suspicion. Really what we are after is proof or at least some strong objective evidence to back up the assertion. Otherwise it isn't science surely.
    I'd assumed that it was not just the abundance of the "right" chemical blend but also the environment in which they are and the sustainability of that environment and/or the necessary changes (at the right time) of the environment. I'm lead to believe that life has never been spontaneously achieved in the lab even by using the right chemicals and a controlled environment? So for it to happen at all thus far appears rather rare and random.
    Last edited by cosmocrazy; 2020-Jan-13 at 03:30 PM.

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    Quote Originally Posted by kzb View Post
    Reptiles are smarter than amphibians. Mammals are smarter than reptiles. Octopus are smarter than jellyfish.
    Yet all (mammals aside since we are descendent s) have successfully survived for a long period of time without too much evolutionary change. What makes humans standout more than all other species is the fact that we arrived in the evolutionary chain late on, yet evolved very quickly in a relatively short time frame into advanced technological species, unique on this planet.

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    Quote Originally Posted by cosmocrazy View Post
    I'd assumed that it was not just the abundance of the "right" chemical blend but also the environment in which they are and the sustainability of that environment and/or the necessary changes (at the right time) of the environment. I'm lead to believe that life has never been spontaneously achieved in the lab even by using the right chemicals and a controlled environment? So for it to happen at all thus far appears rather rare and random.
    Certainly, sometimes I have had this feeling that abiogenesis might be very highly improbable and the strong anthropic principle is the explanation. Yet the experts debunk this idea.

    Also, the standard response is that life on Earth started pretty much immediately after conditions were suitable, so it can't be that improbable.

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    Quote Originally Posted by cosmocrazy View Post
    Yet all (mammals aside since we are descendent s) have successfully survived for a long period of time without too much evolutionary change. What makes humans standout more than all other species is the fact that we arrived in the evolutionary chain late on, yet evolved very quickly in a relatively short time frame into advanced technological species, unique on this planet.
    As I said this used to be my favourite explanation, that the evolution of human-like technological brain power is statistically improbable. But on the other hand, back in the Cambrian period, there were no intelligent life forms whatsoever (outside of Doctor Who).

    Now there are us, whales, elephants, chimps, octopus, dogs, cats....and we are not yet half-way through Earth's lifetime as a planet suitable for complex life.

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    Quote Originally Posted by kzb View Post
    Sometime I think that as well. But then I read something about all the chemicals of life being present all over the place and I change my mind again.

    It's just a suspicion. Really what we are after is proof or at least some strong objective evidence to back up the assertion. Otherwise it isn't science surely.
    I know the elements and simple compounds are all over there.
    What I mean is getting millions of atoms arranged into something complex that is able to replicate and pass hereditary information almost but not quite perfectly accurately.
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    Quote Originally Posted by kzb View Post
    Reptiles are smarter than amphibians. Mammals are smarter than reptiles. Octopus are smarter than jellyfish.
    As I said, one single line of one single branch. Evolutionarily, one twitch of a worm's tail in the Cambrian era, and tetrapods with notochords might never even have been a thing.

    Quote Originally Posted by kzb View Post
    Certainly, sometimes I have had this feeling that abiogenesis might be very highly improbable and the strong anthropic principle is the explanation. Yet the experts debunk this idea.

    Also, the standard response is that life on Earth started pretty much immediately after conditions were suitable, so it can't be that improbable.
    Which experts based on which evidence? Serious question.

    And no, probability does not work like that, and drawing from an example of one is still bad logic.
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    Quote Originally Posted by kzb View Post
    As I said this used to be my favourite explanation, that the evolution of human-like technological brain power is statistically improbable. But on the other hand, back in the Cambrian period, there were no intelligent life forms whatsoever (outside of Doctor Who).

    Now there are us, whales, elephants, chimps, octopus, dogs, cats....and we are not yet half-way through Earth's lifetime as a planet suitable for complex life.
    But we (humans) are the only species that developed into a technological civilisation and in a very short period of time also. Plus, as Noclevername mentioned, there is only one example so far so using it to measure the probability is bad logic. It may well be that the probability of intelligent life evolving is 1 in 10^22+ as we currently observe (based on the number of visible stars). As we all keep saying there is far to much speculation and all we can do is suggest plausible reasons based on currently known mainstream science.

    Its a subject I'm very passionate about and I do enjoy discussing it even if its mainly speculation but you can sort of find some good reasoning if you consider the little evidence we do have.

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    Quote Originally Posted by Noclevername View Post
    As I said, one single line of one single branch. Evolutionarily, one twitch of a worm's tail in the Cambrian era, and tetrapods with notochords might never even have been a thing.



    Which experts based on which evidence? Serious question.

    And no, probability does not work like that, and drawing from an example of one is still bad logic.
    It seems to be accepted in this field that probability does work like that. The fact that life appeared very quickly is taken as evidence that abiogenesis is a likely thing to happen.

    Similarly, the fact that it took 2 or 3 billion years to step up from prokaryotes to eukaryotes is taken in some quarters as evidence that step has a much lower probability of happening.

    Yes it's a sample of one but it's the best logic can do in the circumstances.

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    Also, for arguments sake, imagine that Earth was exceptionally quick at starting life. Say 99th percentile of all habitable planets.

    But then the next factor is going from prokaryotes to eukaryotes, and in this Earth might be slow. Say 99th percentile the other way: exceptionally slow.

    There are a long chain of steps, each with a percentile, in between abiogenesis and human technological civilisation.

    The probability of each step being (say) 99th percentile in the same direction (fast or slow) is tiny.

    Much more statistically probable is that one percentile will compensate for another, so when they multiply together the percentile is much closer to average than any one factor in the chain.

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    But we (humans) are the only species that developed into a technological civilisation

    Being a Devil's advocate, cosmocrazy, I could imagine a Devonian dragonfly thinking (accept for argument) that "we are the only ones to develop winged flight", knowing nothing of birds, pterodactyls and bats.

    The Future is Wild hinted that the squibbon would be the next technological species.
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    Quote Originally Posted by kzb View Post
    It seems to be accepted in this field that probability does work like that.
    Citation needed. Show me the science!
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    Quote Originally Posted by kzb View Post
    It seems to be accepted in this field that probability does work like that. The fact that life appeared very quickly is taken as evidence that abiogenesis is a likely thing to happen.

    Similarly, the fact that it took 2 or 3 billion years to step up from prokaryotes to eukaryotes is taken in some quarters as evidence that step has a much lower probability of happening.

    Yes it's a sample of one but it's the best logic can do in the circumstances.
    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. 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. 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.
    Last edited by cosmocrazy; 2020-Jan-15 at 07:24 AM.

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    Quote Originally Posted by Noclevername View Post
    Citation needed. Show me the science!
    I do not know who first came up with the idea ! It is simply common knowledge in this field, I've seen it written many times.

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