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

  1. #691
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    I don't see a sample size of one as a problem. If I estimate that one planet in a million has life and then I choose one a random, if that one has life then my one in a million estimate is pretty much destroyed. The probability of life is almost certainly much higher. But I do have a problem with choosing earth as the sample. Anyone doing this test must live on a planet that has life, so there's no chance the the test will fail to find life no matter how rare life might be.

  2. #692
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    Quote Originally Posted by Chuck View Post
    I don't see a sample size of one as a problem. If I estimate that one planet in a million has life and then I choose one a random, if that one has life then my one in a million estimate is pretty much destroyed. The probability of life is almost certainly much higher. But I do have a problem with choosing earth as the sample. Anyone doing this test must live on a planet that has life, so there's no chance the the test will fail to find life no matter how rare life might be.
    .. all of which tells us nothing more than we already know .. regardless of the truths of statistical theorems.

  3. #693
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    Quote Originally Posted by kzb View Post
    Without it there is nothing much to go on.
    There IS nothing much to go on!!
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

  4. #694
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    Quote Originally Posted by kzb View Post
    The principle of mediocrity is well entrenched in this field. Without it there is nothing much to go on.
    Yep. At this point it is like debating the number of angels on the head of a pin. I feel some of the speculation can be interesting as long as it isn’t taken too seriously or specific speculation isn’t pushed as being somehow factual.

    Also it is the very basis of the paradox. If you believe that we are a special, one-off event, there is no paradox.
    There also would be no paradox if there were hundreds of billions of other identical human civilizations in the galaxy today, since it would be so difficult to detect them. The paradox is based on speculation about technological and societal developments that we cannot yet know will occur even for humans, let alone any hypothetical ET civilization.

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  5. #695
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    Quote Originally Posted by Noclevername View Post
    There IS nothing much to go on!!
    Exactly.

    "The problem with quotes on the Internet is that it is hard to verify their authenticity." — Abraham Lincoln

    I say there is an invisible elf in my backyard. How do you prove that I am wrong?

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  6. #696
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    Extrapolation from a sample size of one can be immensely entertaining, but it is doubtful if it is science.

    So here, in answer to the OP, are the non-science alternatives

    1. There is no one else.
    2. We are the first. The others have to catch up.
    3. No civilisation in their right mind wastes time communicating over something as ineffectual as the EM spectrum.
    4. "We don't treat with so called civilisations that mess up their own planet."
    5. "We are watching you and when you are, figuratively, fat and juicy enough we'll come for the harvest."
    6. "Shh!. For Pete's sake be quite. The Dark Ones may be listening."
    7. "Do you talk to bacteria on a Petri dish?"
    8. "Have you never heard of reality TV?"
    9. Etc.

  7. #697
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    Quote Originally Posted by Eclogite View Post
    Extrapolation from a sample size of one can be immensely entertaining, but it is doubtful if it is science.

    So here, in answer to the OP, are the non-science alternatives

    1. There is no one else.
    2. We are the first. The others have to catch up.
    3. No civilisation in their right mind wastes time communicating over something as ineffectual as the EM spectrum.
    4. "We don't treat with so called civilisations that mess up their own planet."
    5. "We are watching you and when you are, figuratively, fat and juicy enough we'll come for the harvest."
    6. "Shh!. For Pete's sake be quite. The Dark Ones may be listening."
    7. "Do you talk to bacteria on a Petri dish?"
    8. "Have you never heard of reality TV?"
    9. Etc.
    10. They might exist, but so far off that we can't detect them.
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

  8. #698
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    Quote Originally Posted by Eclogite View Post
    Extrapolation from a sample size of one can be immensely entertaining, but it is doubtful if it is science.

    So here, in answer to the OP, are the non-science alternatives

    1. There is no one else.
    2. We are the first. The others have to catch up.
    3. No civilisation in their right mind wastes time communicating over something as ineffectual as the EM spectrum.
    4. "We don't treat with so called civilisations that mess up their own planet."
    5. "We are watching you and when you are, figuratively, fat and juicy enough we'll come for the harvest."
    6. "Shh!. For Pete's sake be quite. The Dark Ones may be listening."
    7. "Do you talk to bacteria on a Petri dish?"
    8. "Have you never heard of reality TV?"
    9. Etc.
    Scarily enough, number 6 on the list actually stands up to scrutiny !

  9. #699
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    Quote Originally Posted by Chuck View Post
    I don't see a sample size of one as a problem. If I estimate that one planet in a million has life and then I choose one a random, if that one has life then my one in a million estimate is pretty much destroyed. The probability of life is almost certainly much higher. But I do have a problem with choosing earth as the sample. Anyone doing this test must live on a planet that has life, so there's no chance the the test will fail to find life no matter how rare life might be.
    Break down the evolution of humans into stages, starting out at abiogenesis and finishing with 21st century technology.

    Measure or estimate the time taken for each stage on Earth.

    By rules of probability some stages will have taken longer than average and some shorter than average.

    But adding them all together, again by the rules of probability the longer and shorter stages will tend to compensate for each other, so the end total should most likely be near the average.

    Hence the paradox.

  10. #700
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    Quote Originally Posted by Van Rijn View Post
    Yep. At this point it is like debating the number of angels on the head of a pin. I feel some of the speculation can be interesting as long as it isn’t taken too seriously or specific speculation isn’t pushed as being somehow factual.



    There also would be no paradox if there were hundreds of billions of other identical human civilizations in the galaxy today, since it would be so difficult to detect them. The paradox is based on speculation about technological and societal developments that we cannot yet know will occur even for humans, let alone any hypothetical ET civilization.
    Yes that's logical, but as I said before, that is not a nice viewpoint to hold. It means that all species are forever confined to their home systems and no sign of their existence ever gets out very far.

    At some point in the future, Earth will become uninhabitable. This is hundreds of millions of years off (hopefully) and who knows what will be the result of the human race after that time. But going with your viewpoint, even these advanced descendants are doomed to die with the solar system.

  11. #701
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    Quote Originally Posted by kzb View Post
    Break down the evolution of humans into stages, starting out at abiogenesis and finishing with 21st century technology.

    Measure or estimate the time taken for each stage on Earth.

    By rules of probability some stages will have taken longer than average and some shorter than average.

    But adding them all together, again by the rules of probability the longer and shorter stages will tend to compensate for each other, so the end total should most likely be near the average.

    Hence the paradox.
    But 21st century technology is not detectable from any distance. So, even if the Galaxy is teeming with the technological equivalent of us, we still would detect nothing. Hence, there is no paradox.
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

  12. #702
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    Quote Originally Posted by kzb View Post
    Yes that's logical, but as I said before, that is not a nice viewpoint to hold. It means that all species are forever confined to their home systems and no sign of their existence ever gets out very far.
    Whether it is nice or not is irrelevant. Nor do I assume it is true. It is simply a statement about the limitations about what we can currently say. We can’t know if there are civilizations (more or less) like ours elsewhere in the galaxy. We can’t know if there are a lot of them. We can only speculate about what we might do in the future, and therefore can only speculate about what other civilizations, if they exist, might do.

    At some point in the future, Earth will become uninhabitable. This is hundreds of millions of years off (hopefully) and who knows what will be the result of the human race after that time. But going with your viewpoint, even these advanced descendants are doomed to die with the solar system.
    Maybe, but that would be a good long run. I’ll be very impressed if something descended from us lasts 100,000 years and maintains a technological civilization. Even more impressed at a million.

    And then even stay at homes could perhaps move to habitats and live well into the sun’s white dwarf phase, or catch a closely passing star when it gets near (like the one coming by in 1.3 million years). That would be less challenging than more distant interstellar travel.

    But even if they last for a ridiculously long time, it appears the universe will get dark. If true, they would have to end eventually.

    Of course, I don’t assume that an interstellar capable species will automatically take over the galaxy, either, or look at these possibilities as either optimistic or pessimistic. They’re just interesting to think about.

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  13. #703
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    Quote Originally Posted by Tom Mazanec View Post
    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.
    Thanks for this Tom.

    if we assume this 4.2 billion years is typical, the paradox comes from there supposedly being Earth-like planets in existence from 8 billion years ago. There should be a generation of ET's 3 billion years ahead of us.

  14. #704
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    Quote Originally Posted by kzb View Post
    Thanks for this Tom.

    if we assume this 4.2 billion years is typical, the paradox comes from there supposedly being Earth-like planets in existence from 8 billion years ago. There should be a generation of ET's 3 billion years ahead of us.
    Maybe there are. Maybe vastly advanced civilizations exist. If we assume as you say. If we also assume Earthlike planets typically develop life. If we assume planets with life also typically develop intelligence. If we assume intelligence typically leads to space travel. If we assume space travel typically will lead to galactic colonization. If we assume they are still at it. If we assume this activity will be detectable to us at our current level of technology, at the present time.

    Plus many intermediate steps that I've left out; technological lines of development, biological suitability to space travel, etc. Any one of which is enough to derail our scenario.
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

  15. #705
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    Quote Originally Posted by kzb View Post
    Thanks for this Tom.

    if we assume this 4.2 billion years is typical, the paradox comes from there supposedly being Earth-like planets in existence from 8 billion years ago. There should be a generation of ET's 3 billion years ahead of us.
    Actually, the argument in the book is that 4.2 billion years is NOT typical (if I understand it correctly). The argument was that 42 billion, or 42 trillion, is "typical". BUT, you "force" one example to be atypical (because we know that we exist). ALL six steps should average much longer than the age of the universe...and it doesn't matter by how much more one or two are than the others.
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  16. #706
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    Quote Originally Posted by Tom Mazanec View Post
    Actually, the argument in the book is that 4.2 billion years is NOT typical (if I understand it correctly). The argument was that 42 billion, or 42 trillion, is "typical". BUT, you "force" one example to be atypical (because we know that we exist). ALL six steps should average much longer than the age of the universe...and it doesn't matter by how much more one or two are than the others.
    But how have they estimated how long each stage should take?

  17. #707
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    Quote Originally Posted by Noclevername View Post
    Maybe there are. Maybe vastly advanced civilizations exist. If we assume as you say. If we also assume Earthlike planets typically develop life. If we assume planets with life also typically develop intelligence. If we assume intelligence typically leads to space travel. If we assume space travel typically will lead to galactic colonization. If we assume they are still at it. If we assume this activity will be detectable to us at our current level of technology, at the present time.

    Plus many intermediate steps that I've left out; technological lines of development, biological suitability to space travel, etc. Any one of which is enough to derail our scenario.
    Yes a lot of the literature does assume all these things, apart from vastly advanced civilisations existing. Actually, to row back on that a bit, vastly advanced civilisations might exist, but they intentionally hide themselves from us, like the Prime Directive. Or, that they exist but everyone is hiding from The Dark Ones.

  18. #708
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    Quote Originally Posted by Noclevername View Post
    But 21st century technology is not detectable from any distance. So, even if the Galaxy is teeming with the technological equivalent of us, we still would detect nothing. Hence, there is no paradox.
    But the expectation is that 90% of ETs are millions of years ahead of us.

  19. #709
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    Quote Originally Posted by kzb View Post
    Yes a lot of the literature does assume all these things, apart from vastly advanced civilisations existing.
    Then please cite the literature and data that supports this? All I've seen from the authorities on the subject is a lot of speculation without backing.
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  20. #710
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    Quote Originally Posted by kzb View Post
    But the expectation is that 90% of ETs are millions of years ahead of us.
    Whose expectation?
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

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    The filter of war wiped out intelligent alien species.
    As humans shall be wiped out as well... by this coronavirus!

  22. #712
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    Quote Originally Posted by Noclevername View Post
    Whose expectation?
    Somewhere there is an article which calculates how many super-advanced ET's we have to fly past before we meet a species on the same level as us. It's thousands.

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    Quote Originally Posted by kzb View Post
    Somewhere there is an article which calculates how many super-advanced ET's we have to fly past before we meet a species on the same level as us. It's thousands.
    Some article? Not exactly a consensus view, is it? How did they determine there would be super-advanced aliens in the first place? Obviously, it isn’t enough just to consider when a civilization starts, as civilizations can end and species can die out for many reasons. In fact, a common idea I have heard is the idea that technological civilizations don’t last, with a variety of proposed reasons, generally based on problems and close calls we have had.

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    Quote Originally Posted by kzb View Post
    Somewhere there is an article which calculates how many super-advanced ET's we have to fly past before we meet a species on the same level as us. It's thousands.
    This is the crux of the Fermi Paradox. If there were thousands of super-advanced ETs out there, at least one of them would be here; we would be part of their civilisation, and we'd read about their history in schools. We don't, hence paradox.

    There are plenty of proposed solutions, but no-one knows which is right.

  25. #715
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    Quote Originally Posted by eburacum45 View Post
    This is the crux of the Fermi Paradox. If there were thousands of super-advanced ETs out there, at least one of them would be here; we would be part of their civilisation, and we'd read about their history in schools.
    That hasn’t been established. The argument is based on the assumption of a fanatically expansionist immortal civilization. Advanced or not, we don’t know if that assumption would or could apply.

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  26. #716
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    Quote Originally Posted by Van Rijn View Post
    That hasn’t been established. The argument is based on the assumption of a fanatically expansionist immortal civilization. Advanced or not, we don’t know if that assumption would or could apply.
    No, but it is the mainstream view.

    if you Google it you will find loads of articles with this viewpoint. e.g:

    The analysis done here indicates that three-quarters of the Earth-like planets in the Universe are older than the Earth and that their average age is 1.8±0.9 billion years older than the Earth.

    https://www.sciencedirect.com/scienc...19103501966072

    comparing the ages of these systems we estimated that 77% of potentially habitable star systems are on average 3.13 billion years older than the Sun. This suggests that any intelligent life in the Galaxy is likely to be incredibly more advanced than we are assuming that they have evolved under similar timescales than we have

    https://arxiv.org/abs/1509.02832

  27. #717
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    Quote Originally Posted by Van Rijn View Post
    That hasn’t been established. The argument is based on the assumption of a fanatically expansionist immortal civilization. Advanced or not, we don’t know if that assumption would or could apply.
    The idea that none of these hypothetical advanced civilsations are expansionist is one of the possible solutions, but far from the only solution.

  28. #718
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    Quote Originally Posted by kzb View Post
    No, but it is the mainstream view.

    if you Google it you will find loads of articles with this viewpoint. e.g:
    I don’t think “mainstream” is a very useful term in this context, given that it is speculation layered on assumptions. Yes, there are some common lines of speculation, but it appears to be more based on personal preferences and biases that anything else, and it is always easy to say “But ...” Even restricting speculation to known physics may be more game playing than useful here. Who can say if new physics or new observations might lead civilizations to do more interesting things than interstellar expansion?

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  29. #719
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    Quote Originally Posted by kzb View Post
    Somewhere there is an article which calculates how many super-advanced ET's we have to fly past before we meet a species on the same level as us. It's thousands.
    Show it to me, please. I want to know what it says and how it is sourced.

    oops. I see you provided links.
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  30. #720
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    Quote Originally Posted by kzb View Post
    No, but it is the mainstream view.

    if you Google it you will find loads of articles with this viewpoint. e.g:

    The analysis done here indicates that three-quarters of the Earth-like planets in the Universe are older than the Earth and that their average age is 1.8±0.9 billion years older than the Earth.

    https://www.sciencedirect.com/scienc...19103501966072

    comparing the ages of these systems we estimated that 77% of potentially habitable star systems are on average 3.13 billion years older than the Sun. This suggests that any intelligent life in the Galaxy is likely to be incredibly more advanced than we are assuming that they have evolved under similar timescales than we have

    https://arxiv.org/abs/1509.02832
    OK, abstracts, but I want the meat.

    What does the overall weight of evidence say? You invoked statistics, so let's do some. What are the numbers? I feel like I'm getting nowhere with this discussion.
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

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