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

  1. #31
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    I don't know, do we start with the assumption that we are typical observers, or special observers?

    From Conflict Between Anthropic Reasoning and Observation: Anthropic reasoning often begins with the premise that we should expect to find ourselves typical among all intelligent observers. However, in the infinite universe predicted by inflation, there are some civilizations which have spread across their galaxies and contain huge numbers of individuals. Unless the proportion of such large civilizations is unreasonably tiny, most observers belong to them.
    Thus anthropic reasoning predicts that we should find ourselves in such a large civilization, while in fact we do not. There must be an important flaw in our understanding of the structure of the universe and the range of development of civilizations, or in the process of anthropic reasoning.


    But then Brane Worlds, the Subanthropic Principle and the Undetectability Conjecture follows with In the recent article ‘Conflict between anthropic reasoning and observation’ Ken D. Olum, using some inflation-based ideas and the anthropic premise that we should be typical among all intelligent observers in the Universe, arrives at the puzzling conclusion that ‘we should find ourselves in a large civilization (of galactic size) where most observers should be, while in fact we do not’. In this note we discuss the intriguing possibility whether we could be in fact immersed in a large civilization without being aware of it. Our conclusion is that this possibility cannot be ruled out provided two conditions are met, that we call the Subanthropic Principle and the Undetectability Conjecture. The Subanthropic Principle states that we are not typical among the intelligent observers from the Universe. Typical civilizations of typical galaxies would be hundreds of thousands, or millions, of years more evolved than ours and, consequently, typical intelligent observers would be orders of magnitude more intelligent than us. The Undetectability Conjecture states that, generically, all advanced civilizations camouflage their planets for security reasons, so that no signal of civilization can be detected by external observers, who would only obtain distorted data for dissuasion purposes. These conditions predict also a low probability of success for the SETI project. We also argue that it is brane worlds, and not inflation, what dramatically could aggravate the ‘missing-alien’ problem pointed out first in the fifties by Enrico Fermi.


    I think the only way this "paradox" gets resolved is when ETi, if it exists, reveals itself.
    Where the telescope ends, the microscope begins. Which of the two has the greater view?

  2. #32
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    Quote Originally Posted by Dave241 View Post

    Again, you are trying to make the point of "if we can't do it today, it's impossible". I reject this outright.
    Sorry, I'm kind of resurrecting this thread, stimulated by the other thread on the paradox. I don't think that Colin or I were saying that it's forever impossible just because we can't do it today. Just that it might be infeasible, which would explain it. It's only "my favorite explanation," not "an explanation that I claim is absolutely true."

    Earlier in the thread you said this:

    Actually, I'm assuming a space craft capable of operating indefinitely without a pit stop. The sort of craft I am envisioning would essentially be a small country of hundreds of thousands of people with every industry already present onboard the ship. All the ship would need is an influx of energy to keep going, everything else would be self sustainable even to the point that they could build and replace entire sections of their ship as they went.
    Fine, but the influx of energy seems like a big problem to me. On a voyage of hundreds or thousands of years, where are you going to get that energy? Perhaps a fusion reactor, but we don't know how feasible it is to make such a reactor.
    As above, so below

  3. #33
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    Quote Originally Posted by Tom Mazanec View Post
    I think the reason is that it is extremely hard to get abiogenesis. Once you get a protobacterium which can multiply and mutate, natural selection insures evolution and that promotes increasing complexity.
    But even a protobacterium would be as complex as iPhone X. To form such without Darwinian evolution may take a trillion years on average, and Earth was freakishly early.
    The Fermi paradox is very puzzling.

    There have been many similar threads on here over the years and we have never solved it.

    I think maybe we have to revisit your point about the possible uniqueness of abiogenesis on Earth.

    Where is the Great Filter? Abiogenesis or sometime later? Maybe the answer is staring us in the face, it's abiogenesis, because all subsequent stages seem inevitable given billions of years of time.

    Certainly we need to start thinking outside the box, because all explanations up to now seem to have serious problems once you look into them.

  4. #34
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    The Fermi Paradox bothers me because too many assumptions are tied into it. In a sense, it strikes me as almost meaningless, trying to define something we know too little about at present.

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    Quote Originally Posted by Jens View Post
    Sorry, I'm kind of resurrecting this thread, stimulated by the other thread on the paradox. I don't think that Colin or I were saying that it's forever impossible just because we can't do it today. Just that it might be infeasible, which would explain it. It's only "my favorite explanation," not "an explanation that I claim is absolutely true."

    Earlier in the thread you said this:



    Fine, but the influx of energy seems like a big problem to me. On a voyage of hundreds or thousands of years, where are you going to get that energy? Perhaps a fusion reactor, but we don't know how feasible it is to make such a reactor.
    Remember we are talking millions or billions of years here not a few centuries or millennia.

    Having said that, we can see in the next few centuries there will be artificial intelligence.

    Even now there are people saying the first immortal people may already have been born.

    There will be advances in biology where humans can be grown without a human host, "born" and raised by robots.

    Very shortly (compared to the age of the galaxy) the time barrier to interstellar journeys will more or less disappear for us. If that happens here, it should've happened billions of years ago for other civilisations.

  6. #36
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    Quote Originally Posted by Roger E. Moore View Post
    The Fermi Paradox bothers me because too many assumptions are tied into it. In a sense, it strikes me as almost meaningless, trying to define something we know too little about at present.
    I see what you are saying definitely. We need more information to work on.

    That should be forthcoming in the not to distant future, as exoplanet observations improve.

    It's possible a game-changer event could occur, such as discovering independently -evolved life on Mars or outer moons. That would certainly answer a few questions.

  7. #37
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    Part of my concern is how we define intelligence, and part is whether any life we encounter is capable of communication with us, or we with it. It's like the Solaris problem--you "know" the alien is intelligent, but it isn't intelligent in the way you traditionally thought of intelligence. How it communicates with you might also be confounded, with the two sides operating on completely different levels with completely different assumptions and intentions/goals.

    I just read an article about logical fallacies, particularly whether the absence of evidence equals evidence of absence. It doesn't. Just because we can't find it anywhere does not mean it is not there. It might be that we aren't looking at the right things, or that we are not looking at the problem in the right way. It is too early to say.
    Last edited by Roger E. Moore; 2019-Apr-23 at 02:49 PM.

  8. #38
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    Here is another way of looking at the Fermi Paradox: If there are other intelligent species of life on Earth, why aren't they communicating with us?

    Answer: They already are communicating with us.

    Chimpanzees and certain crows make and use tools, have complex social structures, and clearly communicate among themselves within their own species. We can train crows and teach sign language to chimps; the crows and chimps can communicate certain needs to us ("Leave me alone." "Feed me." "Pay attention to me."), with chimps possibly telling us a lot more than that. Dolphins don't use tools but pretty clearly communicate among themselves and are able to be trained and communicate with us. Chimps and dolphins demonstrate creativity. And then there's octopi, but let's move on.

    The issue becomes, if these are not the intelligent species we were looking for, then what exactly are we looking for? Can we even articulate what we hope to find?

    Turn the problem around: How would an alien species decide whether we are intelligent? We can't say as we do not know what assumptions those aliens have about intelligence.

    In a sense, I am hopeful we can communicate with other forms of life. My wife and I live in a house with ten (10) cats. I am positive, every single day, that I can communicate effectively with each of those cats, and my arms and fingers have the scars to prove it.

    But the Solaris problem lingers. We are forced to rely on science fiction and storytelling to make sense of the problem and see the limitations of finding intelligent life and knowing for certain that that life is intelligent, and this is fine but it is all we have.

  9. #39
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    The Medusan Problem, Part I: Let’s make up a hypothetical race of aliens like disembodied brains, creatures that look like mile-long clusters of hydrogen-filled balloons with jellyfish tentacles going down and things like sails on top, to catch the wind and move about while they float high in the atmosphere of Jupiter. (We are stealing this idea from Carl Sagan and Arthur C. Clarke simultaneously.) Those brains have an organic biochemistry based on hydrocarbons. They float around in the air all day feeding on little floating and flying alien life forms, never touching bottom because for practical purposes there isn’t any bottom on Jupiter, you just go down until the pressure squashes you. When one of the creatures is no longer able to generate the hydrogen to keep it afloat, it sinks and dies.

    These, um, Medusans communicate by sound waves for millions of years, sort of like whales—and us—but then they figure out radio, using their littlest tentacles and bits of metallic stuff that accumulate on their gill-sails. Now they have something like planetary telepathy, almost instantaneous communication over an area vastly bigger than that of Earth, quadrillions of these guys in billions of clan herds, all talking at once since there’s not much else to do on Jupiter except talk, eat, and fertilize egg masses all at once. Think of intensely social jellyfish with cell phones. They’re super smart, so they build bigger and bigger radios and even make balloons to carry relay stations high in the atmosphere to travel all over Jupiter.

    Then they figure out how to make radio telescopes and detect signals from other planets—well, from their sky, really, since they don’t have eyes that can see planets. They screw up at first and think everything they detect is from intelligent life, but they get that straightened out and start looking for real intelligent life.

    If they detected radio signals from Earth, would they know those signals came from us? Would they understand there was intelligence on Earth, and we were it? Would we even count as intelligent by their standards?

  10. #40
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    Sources for "Medusans"

    https://en.wikipedia.org/wiki/A_Meeting_with_Medusa
    A Meeting with Medusa is a science fiction novella by British writer Arthur C. Clarke. It was originally published in 1971 and has since been included in the anthology Nebula Award Stories Eight as well as several collections of Clarke's writings. A sequel, The Medusa Chronicles, was published in 2016 as a collaborative effort between Alastair Reynolds and Stephen Baxter.

    ===

    http://cdsads.u-strasbg.fr/abs/1976ApJS...32..737S

    "Particles, environments, and possible ecologies in the Jovian atmosphere"
    Sagan, C.; Salpeter, E. E.
    Astrophysical Journal Supplement Series, vol. 32, Dec. 1976, p. 737-755

    Abstract: The possible existence of indigenous Jovian organisms is investigated by characterizing the relevant physical environment of Jupiter, discussing the chromophores responsible for the observed coloration of the planet, and analyzing some permissible ecological niches of hypothetical organisms. Values of the eddy diffusion coefficient are estimated separately for the convective troposphere and the more stable mesosphere, and equilibrium condensation is studied for compounds containing Na, Cl, or both. The photoproduction of chromophores and nonequilibrium organic molecules is analyzed, and the motion of hypothetical organisms is examined along with the diffusion of metabolites and the consequent growth of organisms. Four kinds of organisms are considered: primary photosynthetic autotrophs ('sinkers'), larger autotrophs or heterotrophs that actively maintain their pressure level ('floaters'), organisms that seek out others ('hunters'), and organisms that live at almost pyrolytic depths ('scavengers'). It is concluded that ecological niches for sinkers, floaters, and hunters appear to exist in the Jovian atmosphere.

    ===

    https://web.archive.org/web/20180124...fish-in-space/
    Fantastic photographs of floating jellyfish, to get in the mood (ha ha)

    https://web.archive.org/web/20190423...om/wiki/Jovian
    Another view with excellent artwork on Jovian aliens, great yellow pic with "gasbags"

    https://www.sciencemag.org/news/2016...s-failed-stars
    Certain cool Y-type brown dwarfs could be good places for atmospheric life, as envisioned for Jupiter.

    FROM:
    http://cdsads.u-strasbg.fr/abs/2017ApJ...836..184Y
    Atmospheric Habitable Zones in Y Dwarf Atmospheres
    Yates, Jack S.; Palmer, Paul I.; Biller, Beth; Cockell, Charles S.
    The Astrophysical Journal, Volume 836, Issue 2, article id. 184, 10 pp. (2017). (ApJ Homepage)

    We use a simple organism lifecycle model to explore the viability of an atmospheric habitable zone (AHZ), with temperatures that could support Earth-centric life, which sits above an environment that does not support life. To illustrate our model, we use a cool Y dwarf atmosphere, such as WISE J085510.83-0714442.5, whose 4.5-5.2 mum spectrum shows absorption features consistent with water vapor and clouds. We allow organisms to adapt to their atmospheric environment (described by temperature, convection, and gravity) by adopting different growth strategies that maximize their chance of survival and proliferation. We assume a constant upward vertical velocity through the AHZ. We found that the organism growth strategy is most sensitive to the magnitude of the atmospheric convection. Stronger convection supports the evolution of more massive organisms. For a purely radiative environment, we find that evolved organisms have a mass that is an order of magnitude smaller than terrestrial microbes, thereby defining a dynamical constraint on the dimensions of life that an AHZ can support. Based on a previously defined statistical approach, we infer that there are of the order of 109 cool Y brown dwarfs in the Milky Way, and likely a few tens of these objects are within 10 pc from Earth. Our work also has implications for exploring life in the atmospheres of temperate gas giants. Consideration of the habitable volumes in planetary atmospheres significantly increases the volume of habitable space in the galaxy.
    Last edited by Roger E. Moore; 2019-Apr-23 at 02:41 PM. Reason: more

  11. #41
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    On a different aspect of this problem: a possible explanation for the Fermi Paradox that involves the willingness to understand others, and why we (and maybe others) are often not willing to do it. Maybe the aliens hear us, get the point, but say "Meh. Why bother."

    https://medicalxpress.com/news/2019-...al-effort.html

    Empathy often avoided because of mental effort
    by American Psychological Association, April 22, 2019

    Even when feeling empathy for others isn't financially costly or emotionally draining, people will still avoid it because they think empathy requires too much mental effort, according to new research published by the American Psychological Association. Empathy, the ability to understand the feelings of another person, is often viewed as a virtue that encourages helping behaviors. But people often don't want to feel empathy.

  12. #42
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    Quote Originally Posted by Roger E. Moore View Post
    The Medusan Problem, Part I: Let’s make up a hypothetical race of aliens like disembodied brains, creatures that look like mile-long clusters of hydrogen-filled balloons with jellyfish tentacles going down and things like sails on top, to catch the wind and move about while they float high in the atmosphere of Jupiter. (We are stealing this idea from Carl Sagan and Arthur C. Clarke simultaneously.) Those brains have an organic biochemistry based on hydrocarbons. They float around in the air all day feeding on little floating and flying alien life forms, never touching bottom because for practical purposes there isn’t any bottom on Jupiter, you just go down until the pressure squashes you. When one of the creatures is no longer able to generate the hydrogen to keep it afloat, it sinks and dies.

    These, um, Medusans communicate by sound waves for millions of years, sort of like whales—and us—but then they figure out radio, using their littlest tentacles and bits of metallic stuff that accumulate on their gill-sails. Now they have something like planetary telepathy, almost instantaneous communication over an area vastly bigger than that of Earth, quadrillions of these guys in billions of clan herds, all talking at once since there’s not much else to do on Jupiter except talk, eat, and fertilize egg masses all at once. Think of intensely social jellyfish with cell phones. They’re super smart, so they build bigger and bigger radios and even make balloons to carry relay stations high in the atmosphere to travel all over Jupiter.

    Then they figure out how to make radio telescopes and detect signals from other planets—well, from their sky, really, since they don’t have eyes that can see planets. They screw up at first and think everything they detect is from intelligent life, but they get that straightened out and start looking for real intelligent life.

    If they detected radio signals from Earth, would they know those signals came from us? Would they understand there was intelligence on Earth, and we were it? Would we even count as intelligent by their standards?
    It doesn't matter. There is nothing to stop diverse forms of life and intelligence existing in theory. But using this as an explanation of the FP means that every single intelligent life form is widely divergent from human.

    It may be that human like intelligence is a subset of intelligence generally, but your explanation means it has to be unique. Bearing in mind there are lots of sunlike stars and rocky planets in their habitable zones, we would not expect this uniqueness?

  13. #43
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    Quote Originally Posted by kzb View Post
    It doesn't matter. There is nothing to stop diverse forms of life and intelligence existing in theory. But using this as an explanation of the FP means that every single intelligent life form is widely divergent from human.

    It may be that human like intelligence is a subset of intelligence generally, but your explanation means it has to be unique. Bearing in mind there are lots of sunlike stars and rocky planets in their habitable zones, we would not expect this uniqueness?
    Mmm, yeah, I see your point. I realize that I am leaning more to the possibility that intelligence might reside largely in beings who resemble oceanic non-technological beings on our Earth, like dolphins, whales, jellyfish, etc. They might be on waterworlds or planetary atmospheres. In other words, most intelligent beings would not be tech-users on our level, building rockets to visit elsewhere. They might be planet-bound. On reflection I realize that was where I was ultimately going.

  14. #44
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    Quote Originally Posted by Roger E. Moore View Post
    On a different aspect of this problem: a possible explanation for the Fermi Paradox that involves the willingness to understand others, and why we (and maybe others) are often not willing to do it. Maybe the aliens hear us, get the point, but say "Meh. Why bother."

    https://medicalxpress.com/news/2019-...al-effort.html

    Empathy often avoided because of mental effort
    by American Psychological Association, April 22, 2019

    Even when feeling empathy for others isn't financially costly or emotionally draining, people will still avoid it because they think empathy requires too much mental effort, according to new research published by the American Psychological Association. Empathy, the ability to understand the feelings of another person, is often viewed as a virtue that encourages helping behaviors. But people often don't want to feel empathy.
    Why are we so interested in contacting ET anyway?

    Possibly dolphins and elephants tick many of the boxes for intelligence. But we're not particularly bothered.

    Why ? Because what we are interested in is learning useful stuff from them. We want to know about their science, culture and philosophy.

    No-one is going to pay untold trillions to communicate with some creature like a dolphin, can it recognise itself in a mirror, that kind of thing. We want something comparable to us, but different.

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    Quote Originally Posted by kzb View Post
    It doesn't matter. There is nothing to stop diverse forms of life and intelligence existing in theory. But using this as an explanation of the FP means that every single intelligent life form is widely divergent from human.

    It may be that human like intelligence is a subset of intelligence generally, but your explanation means it has to be unique. Bearing in mind there are lots of sunlike stars and rocky planets in their habitable zones, we would not expect this uniqueness?
    Why not?

    Also, it could just mean no nearby humanlike thinkers, within our pitiful sensing range. Something similar to us could exist too far away to detect.

    And how long would they remain like us before changing or evolving? We're on the brink of altering our own species, genetically and cybernetically. We'd have to catch hypothetical intelligences at just the right moment in their existence, when they're mature enough to have detectable tech but not so advanced as to be incomprehensible.
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

  16. #46
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    Quote Originally Posted by Noclevername View Post
    Why not?

    Also, it could just mean no nearby humanlike thinkers, within our pitiful sensing range. Something similar to us could exist too far away to detect.

    And how long would they remain like us before changing or evolving? We're on the brink of altering our own species, genetically and cybernetically. We'd have to catch hypothetical intelligences at just the right moment in their existence, when they're mature enough to have detectable tech but not so advanced as to be incomprehensible.
    Absolutely!
    Its like looking for a needle in a hay stack! Only imagine, you are faced with billions of hay stacks and your task is to find a needle or few. But you don't know which hay stacks contain the needles (if any), what the needles look like, how many there could be and at what point in time the needles end up there and hopefully before they rust away. All you can do is hope that there is at least one needle in every hay stack that you might recognise and you happen to come across it just at the right time.

    Well, based on this analogy we have just started to search the first hay stack, the nearest one to us and we have no idea what needle we are looking for, or if indeed there is one in there...

  17. #47
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    so, the conclusion from this paradox is that leaving your star system is really difficult, or really dangerous, or civilisation is rare and short lived. We could take a message from that.
    sicut vis videre esto
    When we realize that patterns don't exist in the universe, they are a template that we hold to the universe to make sense of it, it all makes a lot more sense.
    Originally Posted by Ken G

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    Quote Originally Posted by Noclevername View Post
    We'd have to catch hypothetical intelligences at just the right moment in their existence, when they're mature enough to have detectable tech but not so advanced as to be incomprehensible.
    Bravo. Well put. Standing ovation.

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    Quote Originally Posted by Noclevername View Post
    Why not?

    Also, it could just mean no nearby humanlike thinkers, within our pitiful sensing range. Something similar to us could exist too far away to detect.

    And how long would they remain like us before changing or evolving? We're on the brink of altering our own species, genetically and cybernetically. We'd have to catch hypothetical intelligences at just the right moment in their existence, when they're mature enough to have detectable tech but not so advanced as to be incomprehensible.
    Sorry don't agree with this.

    The reason being, if they are anything like us, they, or their machines, will spread through the galaxy.

    It only takes ONE vaguely human-like intelligence to evolve, in the billions of years before we came along, and your argument fails.

  20. #50
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    Quote Originally Posted by Roger E. Moore View Post
    Bravo. Well put. Standing ovation.
    Not from me I'm afraid. Between those extremes they'd have colonised the galaxy. Their presence, or their past presence, would be obvious.

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    I agree. besides--there has to be a first. I think we're it.

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    Quote Originally Posted by profloater View Post
    so, the conclusion from this paradox is that leaving your star system is really difficult, or really dangerous, or civilisation is rare and short lived. We could take a message from that.
    Their is a Great Filter somewhere along the chain but it does not have to be one of these reasons.

    I don't accept the first two, for reasons I gave upthread.

    The short-lived civilisation reason was fashionable in the cold war epoch for obvious reasons. It may be gaining traction again now because people again feel doomed with climate change. Certainly it has been given a lot of credibility.

    I'm not so sure myself. Even if the current economy collapses, knowledge is not destroyed.

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    Quote Originally Posted by publiusr View Post
    I agree. besides--there has to be a first. I think we're it.
    If we're the first, that logically means the likelihood of evolving technological civilisation is extremely small.

    As well as being the first we are likely to be the only one. This is what logically follows given the timescale of the galaxy.

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    Quote Originally Posted by kzb View Post
    Even if the current economy collapses, knowledge is not destroyed.
    No, but an industrial base can be.
    https://www.inc.com/justin-bariso/el...-sentence.html

    tribal knowledge can be lost if infrastructure isn't maintained.

    if I were an internet billionair--I might still produce a limited line of obsolete type items--tube TVs, etc--just to keep a knowledge base.

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    Quote Originally Posted by kzb View Post
    Sorry don't agree with this.

    The reason being, if they are anything like us, they, or their machines, will spread through the galaxy.

    It only takes ONE vaguely human-like intelligence to evolve, in the billions of years before we came along, and your argument fails.
    What if they didn't? Human style techno-civ tendencies might be more rare than galaxies. Or highly advanced intelligence might be non-expansive.
    Last edited by Noclevername; 2019-Apr-24 at 09:57 PM.
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

  26. #56
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    Quote Originally Posted by kzb View Post
    Their is a Great Filter somewhere along the chain but it does not have to be one of these reasons.

    I don't accept the first two, for reasons I gave upthread.

    The short-lived civilisation reason was fashionable in the cold war epoch for obvious reasons. It may be gaining traction again now because people again feel doomed with climate change. Certainly it has been given a lot of credibility.

    I'm not so sure myself. Even if the current economy collapses, knowledge is not destroyed.
    I fear you are wrong about losing knowledge and history shows a series of ups and downs in civilisation with many explanations but to expect a long steady rise now is maybe optimistic from that historical perspective. When I say leaving a star system is difficult, I include the problem of the short lives of life forms. Even given the long travel times that interstellar travel requires, the billions of years cited in the paradox does imply that it is rare to non existent. We may indeed be the first and only but the numbers would suggest life does get started if the environment is right, but the interstellar distances remain a barrier for all the life forms we might expect to evolve. We include interstellar travel for atoms because of our model of how elements form in supernovas and therefore the transport of seeds or other DNA type molecules must be possible, but intelligence is a big leap of evolution on top of that.
    sicut vis videre esto
    When we realize that patterns don't exist in the universe, they are a template that we hold to the universe to make sense of it, it all makes a lot more sense.
    Originally Posted by Ken G

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    Quote Originally Posted by publiusr View Post
    besides--there has to be a first. I think we're it.
    I agree with you, or at least I feel at present this is highly probable. If you consider the estimated total life span of the universe and compare that to the current estimated age, then the universe is still very much a baby. If we are the first and the only one, that makes us very special and as profloater was eluding to - delicate.

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    Quote Originally Posted by Noclevername View Post
    What if they didn't? (1) Human style techno-civ tendencies might be more rare than galaxies (2). Or highly advanced intelligence might be non-expansive. (3)
    (1) I said if they were even vaguely like us. It's reasonable to expect this, because of the law of mediocrity. Anyhow, if ET was commonplace, it would only take one out of many to spread through the galaxy.

    (2) Going by appearances this is about the one fact we have to work with. Yes human style civs seem to be vanishingly rare, so much so that we appear unique. But that's not enough, you can't just say ET is not observed because he does not exist. You have to say WHY ET does not exist. And this is a big problem, because life started pretty quickly on Earth, and many argue that the evolutionary steps that lead to us are pretty much inevitable given enough time.

    (3) See (1)

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    Quote Originally Posted by publiusr View Post
    I agree. besides--there has to be a first. I think we're it.
    Well it certainly looks like it. But the question is why?

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    Quote Originally Posted by profloater View Post
    I fear you are wrong about losing knowledge and history shows a series of ups and downs in civilisation with many explanations but to expect a long steady rise now is maybe optimistic from that historical perspective. When I say leaving a star system is difficult, I include the problem of the short lives of life forms. Even given the long travel times that interstellar travel requires, the billions of years cited in the paradox does imply that it is rare to non existent. We may indeed be the first and only but the numbers would suggest life does get started if the environment is right, but the interstellar distances remain a barrier for all the life forms we might expect to evolve. We include interstellar travel for atoms because of our model of how elements form in supernovas and therefore the transport of seeds or other DNA type molecules must be possible, but intelligence is a big leap of evolution on top of that.
    I dealt with the lifespan issue upthread. It will disappear as a problem.

    I tend to agree that intelligence of our sort is a big leap, I've said before that the dinosaurs ruled for 160 million years with brains the size of walnuts.

    But others argue it is kind of inevitable. Before the asteroid strike dinosaurs were evolving bigger brains.

    Some argue there would've been a velociraptor technological civilisation evolved millions of years ago if the dinosaurs had not been wiped out.

    Without that asteroid the Milky Way would've been taken over by Velociraptors by now.

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