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Thread: Study says we are probably alone in the universe

  1. #61
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    Quote Originally Posted by The Backroad Astronomer View Post
    Let us say that the two of us land on an deserted island. You sit there and ran calculations on the chances of other humans on the island and figure that there is none, and I look around and find a tiny piece of paper.
    Is there human life on the island, a great chance of life on the island or no life on the island?
    "Paper" is an industrial construct so that by itself your attempted analogy is flawed from the beginning. We didn't find "paper", we found "fiber". Fiber can be used to make paper, but fiber by itself is naturally occurring material.

  2. #62
    Quote Originally Posted by Exposed View Post
    The original paper does not reference these organic molecules as hydrophobic molecules and the presence of complex carbon molecules are not itself indicative of "life" any less different than considering methane or ammonia as indicative of life as well. The paper even describes the process of the film forming via natural geothermal activity.

    The only one "jumping to conclusions" is yourself as you have shown in that thread, because you already are convinced of the "answer" in this one.

    https://www.forbes.com/sites/startsw.../#46842264d684




    Are you stating outright there IS "life" elsewhere in the universe without any observational or experimental evidence? How do you determine what is "wrong" and what is "right"?



    Funding for SETI is the last of our worries if sound scientific principals are tossed aside for assumptions taken for fact such as "the universe is immense so there's your answer".



    Again, I am not saying there is no "life" elsewhere in the universe. What I AM saying is that this question needs to be approached scientifically and not under the guise of faith ("I believe we cannot be alone in the universe") or flawed assumptions ("the universe is too big, therefore we cannot possibly be alone"). Not only is that kind of bias against every known scientific principal, it essentially muddies any kind of objective reasoning...which is clearly shown in your Enceladus thread.
    If you listen to the June 27 episode of TWIS at they end they say mentioned hydrophobic molecules so I might of taken their word without checking it out, but is an organic compound. And if you read the complete thread you realize that I realized after a little time.

    It is a large place and I think it is arrogant that there is only one intelligent species out there.

    In Science you need evidence to back up theories and models.
    Last edited by The Backroad Astronomer; 2018-Jul-07 at 11:40 PM.
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  3. #63
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    Quote Originally Posted by The Backroad Astronomer View Post
    If you listen to the June 27 episode of TWIS at they end they say mentioned hydrophobic molecules so I might of taken their word without checking it out, but is an organic compound. And if you read the complete thread you realize that I realized after a little time.

    It is a large place and I think it is arrogant that there is only thing out there.

    In Science you need evidence to back up theories and models.
    Ok, my apologies as I did not listen to the podcast. If they did mention "hydrophobic molecules" then I understand where the misunderstanding came from.

    It is a large place and I think it is arrogant that there is only thing out there.

    In Science you need evidence to back up theories and models.
    I don't think you realize the two statements above are mutually conflicting. The former is an arrogant statement in itself, because it assumes there IS life out there without having to do any science. The latter is what matters, and if you agree with me that scientific principals, process, theories, experimentation and observations, etc.. are the pinnacles of understanding our universe then I cannot possibly fathom how you can believe in the former, at least without not specifically acknowledging it is just a belief.
    Last edited by Exposed; 2018-Jul-07 at 11:43 PM.

  4. #64
    Quote Originally Posted by Exposed View Post
    "Paper" is an industrial construct so that by itself your attempted analogy is flawed from the beginning. We didn't find "paper", we found "fiber". Fiber can be used to make paper, but fiber by itself is naturally occurring material.
    The point is we found something man made. So therefore a possibility human life on the island.
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  5. #65
    I don't like religious debates no one wins, this is the weirdest on in a long time because the one is accusing the other of being religious.
    Last edited by The Backroad Astronomer; 2018-Jul-08 at 12:03 AM.
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    After Moderator discussion this thread has been moved to Life in Space

  7. #67
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    Quote Originally Posted by Exposed View Post
    Claiming "we are not alone in the universe" as if it's fact without any sort of evidence other than faith because "the universe is immense" is also jumping to conclusions. The sole purpose of the thought experiment, which demonstrates the staggering genetic variation we have, is to show you can have situations where probabilistic constructs of life can exceed the number of stars in the universe, nothing more.

    Other than that, I whole heartedly agree with you finding evidence by testing compounds and exploring other bodies and countless other scientific methods is the more logical approach. My only issue is that when these routinely come back negative the fallback is "an absence of evidence is not evidence of absence", a very convenient loophole that allows you to keep your faith regardless of what the science and numbers show.
    Do you think we've reached the stage in exploring other bodies where we can say that tests for life "routinely come out negative"? Or are you saying that's a stage we might reach later on?

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    Quote Originally Posted by Exposed View Post
    The variable traits and probability of going from random chemical reactions to DNA (and thus multi-cellular organisms) is likely a number even far exceeding that, so yes it is entirely possible this universe may not have "life" anywhere else in the universe. That's all I'm saying.
    The probability of jumping from random chemical reactions to DNA is indeed extremely low. But does the emergence of life require such a jump?

    In an out-of-equilibrium environment, the chemical reactions are not random... And out-of-equilibrium chemical environments are not rare. At least two in this solar system...
    Last edited by Colin Robinson; 2018-Jul-09 at 12:06 PM.

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    I wonder if the authors of the study had decided on a conclusion and then tweaked their model to get the desired result. No one has any data to contradict just about any result about extrasolar life that doesn’t involve space-faring aliens commuting through the solar neighborhood.
    Last edited by swampyankee; 2018-Jul-09 at 10:15 AM.

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  10. #70
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    Quote Originally Posted by swampyankee View Post
    I wonder if the authors of the study had decided on a conclusion and then tweaked their model to get the desired result. No one has any data to contradict just about any result about extrasolar life that doesn’t involve space-faring aliens commuting through the solar neighborhood.
    No I think they did it in an honest fashion. The uncertainty ranges for each factor where found via literature searches. They did not make up the values themselves.

  11. #71
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    Quote Originally Posted by The Backroad Astronomer View Post
    I don't like religious debates no one wins, this is the weirdest on in a long time because the one is accusing the other of being religious.
    Its not a religious debate, its a scientific one. Exposed mentioned that "believing" that life exists elsewhere in the universe requires "faith". Unfortunately Exposed is quite correct, since there is no evidence of life elsewhere (yet) then we can only make assumptions. You are free to assume what ever you like.

    My personal assumption is that life will exist elsewhere in the universe. I can then go on to "believe" life exists elsewhere because like you and many others, the universe seems to me to be an extremely large place for only us to exist in. But there is no evidence to support my belief so therefore I must have "faith" in my reasoning and assumptions.

    It would be arrogant of me to state - life must exist simply because the universe is to large for it not to without any scientific evidence to support my belief. It would be much better for me to say "I believe that life exists elsewhere because I feel that the universe is so large it would seem unlikely that life is unique to one place"

    Can you now see what Exposed is arguing?

  12. #72
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    Quote Originally Posted by kzb View Post
    No I think they did it in an honest fashion. The uncertainty ranges for each factor where found via literature searches. They did not make up the values themselves.
    And I don't even think saying the authors concluded that we are the only life in the universe is a fair reading of the paper. My reading is that they started with the Fermi paradox: that a typical calculation of the probability of technological life via something like the Drake equation tends to produce a pretty high likelihood of a large number of civilizations in any given galaxy, including some that should probably be close enough to detect (and with at least the possibility that an early civilization could have colonized much or all of the galaxy). Yet we don't see any signs of that being the case. So we imagine that some of our assumptions must be wrong, since our observations don't seem to match our predictions.

    Many people have targeted the observation end of things, trying to explain why we don't see anything out there: maybe galactic colonization is very hard, so nobody does it; maybe civilizations inevitably destroy themselves, and so don't stay around long enough for us to see; maybe civilizations make a point of not broadcasting their presence; maybe there's a bottleneck to technological life that we've already passed through. The trouble with any of these types of explanations is that they pretty much have to be true for every single other civilization. Just one expansionist colonizing civilization starting out a few tens of millions of years ago should have completely occupied the galaxy.

    So the authors of this paper seem to have looked at a different possibility: what if we're assessing the probabilities wrong in the first place? So they take another look at the Drake equation, not just plugging in estimates for the various values, but also taking into account the (genuinely pretty large) amount of uncertainty in some of the later terms, and look again at the results we get when doing that. It turns out that we end up with different overall probabilities, including a fairly substantial chance that we are in fact alone in the galaxy. If that's the case, we don't need an exotic explanation for why we don't see other technological civilizations* out there. So I don't think that they're insisting that their work shows that we must be alone. Only that it's a sufficiently likely possibility that we don't need to work hard to come up with an explanation if our observations continue to suggest that to be the case.


    * And note that the Drake equation is definitely talking about technological civilizations, at least capable of broadcasting radio signals, since that's something we could detect. There's not any conflict with observation if there are microbes or even things on the level of plants or animals all over the place. That would be one of the "Great Filter" explanations, that life may be common, but intelligent life is extremely rare.
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  13. #73
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    Thanks for that, it makes mores sense . There is an assumption that advanced civilistations occupy their galaxy but that is hubris, we know that there is also the chance of self destruction and repeated cycles of limited advance, rather like we have now. I believe the chance of our radio emissions etc being visible on another star is also small, very small on distant stars even if they are looking.
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    Quote Originally Posted by Grey View Post
    And I don't even think saying the authors concluded that we are the only life in the universe is a fair reading of the paper. My reading is that they started with the Fermi paradox: that a typical calculation of the probability of technological life via something like the Drake equation tends to produce a pretty high likelihood of a large number of civilizations in any given galaxy, including some that should probably be close enough to detect
    That "should be close enough to detect" seems questionable. Do we know what a technological (radio-capable) civilisation would look like or sound like when it is more than about a century old?

    (and with at least the possibility that an early civilization could have colonized much or all of the galaxy). Yet we don't see any signs of that being the case. So we imagine that some of our assumptions must be wrong, since our observations don't seem to match our predictions.[
    Many people have targeted the observation end of things, trying to explain why we don't see anything out there: maybe galactic colonization is very hard, so nobody does it; maybe civilizations inevitably destroy themselves, and so don't stay around long enough for us to see; maybe civilizations make a point of not broadcasting their presence; maybe there's a bottleneck to technological life that we've already passed through. The trouble with any of these types of explanations is that they pretty much have to be true for every single other civilization. Just one expansionist colonizing civilization starting out a few tens of millions of years ago should have completely occupied the galaxy.
    Just one?

    Earth itself has so far produced just zero instances of an interstellar colonizing civilization (except in fiction).

  15. #75
    The article that I read about it is that they stated SETI should keep looking. One of the main problems I have it is the way it was reported it was it was for sure their would be no life.

    I as far as I am know most scientist think there is life elsewhere based off of the statistics and evidence. I was trying to show exposed that he might of been jumping to conclusions just based off of some math with no evidence.
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  16. #76
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    Quote Originally Posted by Colin Robinson View Post
    That "should be close enough to detect" seems questionable. Do we know what a technological (radio-capable) civilisation would look like or sound like when it is more than about a century old?
    I'm not really sure. Which is probably why it makes sense to assign a pretty high uncertainty to our probability assessment that a civilization will reach a stage where we can detect them, just as the authors of the paper suggest.

    It's tangentially related, but current trends in our ability to analyze transiting exoplanets looks like we'd be able to analyze the atmospheres quite well within a couple decades at most. We might be able to detect the signature of non-technological life pretty far away fairly soon. Not all life would be detectable that way, but if there's anything like our plants out there, it would be hard to come up with a non-biological explanation for an atmosphere full of free oxygen.

    Quote Originally Posted by Colin Robinson View Post
    Just one?
    Yes, pretty much. Let's imagine something that we could probably do if we set our minds to it. Say that we can send out a colony ship every 2,000 years at 1% of the speed of light, that each colony so established will be able to launch it's own colony ships after 2,000 years, and that the distance between suitable planets for colonization is 50 light years at most. That would mean that the number of colony worlds doubles every 2,500 years, or spreads to pretty much every inhabitable world in the galaxy in less than 100,000 years. Even if I slow down the rate of colonization by a factor of 10, a million years is still tiny in terms of galactic timescales. That's the Fermi paradox in a nutshell. Of course, not every civilization would try to do this, and that's one of the possible explanations (I mentioned that above: "maybe galactic colonization is very hard, so nobody does it"). But for any of those explanations, it has to be 100%, and it seems hard to be that certain about the motivations and choices of alien civilizations. If there are a million civilizations in the galaxy and 99.9% never attempt colonization, that still leaves 1,000 species racing to colonize the galaxy first. If 99.9999% of them do not attempt colonization, that one remaining civilization could still be enough to populate the whole galaxy with colonies.
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  17. #77
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    Quote Originally Posted by The Backroad Astronomer View Post
    The article that I read about it is that they stated SETI should keep looking. One of the main problems I have it is the way it was reported it was it was for sure their would be no life.
    I agree that many of the reports of the paper were phrased such that it sounded like they had concluded that there was no other life anywhere. In general, I think it's pretty common for papers to be poorly described in secondary reports; I think it's a really good idea if you read an article that you find interesting, you should track down the original paper and read it.

    Quote Originally Posted by The Backroad Astronomer View Post
    I as far as I am know most scientist think there is life elsewhere based off of the statistics and evidence. I was trying to show exposed that he might of been jumping to conclusions just based off of some math with no evidence.
    I disagree. I think most scientists think that it would be a reasonable possibility for there to be life elsewhere, and we have many tantalizing hints (things like organic molecules in a lot of different environments), but that we don't really have solid evidence of it, and we're left not being sure just how rare or common life really is in the universe.
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  18. #78
    Quote Originally Posted by Grey View Post

    I disagree. I think most scientists think that it would be a reasonable possibility for there to be life elsewhere, and we have many tantalizing hints (things like organic molecules in a lot of different environments), but that we don't really have solid evidence of it, and we're left not being sure just how rare or common life really is in the universe.
    I think most scientists think it is more of in when rather than a if situation. I know of one bet involving a bottle of when if life will be found in our solar system rather than outside the solar system.
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  19. #79
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    Quote Originally Posted by The Backroad Astronomer View Post
    The article that I read about it is that they stated SETI should keep looking. One of the main problems I have it is the way it was reported it was it was for sure their would be no life.

    I as far as I am know most scientist think there is life elsewhere based off of the statistics and evidence. I was trying to show exposed that he might of been jumping to conclusions just based off of some math with no evidence.
    I think it's an interesting angle on the problem. The approach could probably be improved but it's a good start. Other scientists might follow up with similar studies now the idea is out there.

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    Quote Originally Posted by Grey View Post
    It's tangentially related, but current trends in our ability to analyze transiting exoplanets looks like we'd be able to analyze the atmospheres quite well within a couple decades at most. We might be able to detect the signature of non-technological life pretty far away fairly soon. Not all life would be detectable that way, but if there's anything like our plants out there, it would be hard to come up with a non-biological explanation for an atmosphere full of free oxygen.
    That depends on the uncertainties involved in the detection of said 'atmosphere full of free oxygen'.

    Atmospheric free oxygen, alone, is insufficient because there are abiotic explanations. Strong chemical disequilibrium used in conjunction with a detection of free oxygen, (ozone etc), requires evidence of sufficient spectral resolution in order to be able to rule out the possibility of atmospheric chemical disequlibrium being mimicked by closely orbiting exo-moons within the field of view. This in turn, requires that the observed target must be within the high confidence tolerance levels of the observing technology.
    Put simply, we have to 'luck-out' and actually find exactly what we're looking for within 'close' range of Earth .. which comes down to the luck-of-the-draw (which is certainly no guarantee of detecting any such thing).

  21. #81
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    Quote Originally Posted by Grey View Post
    I'm not really sure. Which is probably why it makes sense to assign a pretty high uncertainty to our probability assessment that a civilization will reach a stage where we can detect them, just as the authors of the paper suggest.

    It's tangentially related, but current trends in our ability to analyze transiting exoplanets looks like we'd be able to analyze the atmospheres quite well within a couple decades at most. We might be able to detect the signature of non-technological life pretty far away fairly soon. Not all life would be detectable that way, but if there's anything like our plants out there, it would be hard to come up with a non-biological explanation for an atmosphere full of free oxygen.
    Actually free oxygen can have non-biological explanations, such as water molecules getting broken down by radiation.

    Yes, pretty much. Let's imagine something that we could probably do if we set our minds to it. Say that we can send out a colony ship every 2,000 years at 1% of the speed of light, that each colony so established will be able to launch it's own colony ships after 2,000 years, and that the distance between suitable planets for colonization is 50 light years at most. That would mean that the number of colony worlds doubles every 2,500 years, or spreads to pretty much every inhabitable world in the galaxy in less than 100,000 years. Even if I slow down the rate of colonization by a factor of 10, a million years is still tiny in terms of galactic timescales. That's the Fermi paradox in a nutshell.
    Yes, I think Michael Hart made a calculation like that some years back... But it's one thing to "imagine something that we could probably do if we set our minds to it". It's another thing to actually do it.

    Right now we have one example of radio-capable life, zero examples of interstellar colonization.

    Of course, not every civilization would try to do this, and that's one of the possible explanations (I mentioned that above: "maybe galactic colonization is very hard, so nobody does it"). But for any of those explanations, it has to be 100%, and it seems hard to be that certain about the motivations and choices of alien civilizations. If there are a million civilizations in the galaxy and 99.9% never attempt colonization, that still leaves 1,000 species racing to colonize the galaxy first.
    What if there are a hundred civilisations in a galaxy like ours, and 99.9% never attempt colonization? Wouldn't that mean colonization gets attempted in just one galaxy out of ten?

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    Quote Originally Posted by Colin Robinson View Post
    <EDIT>



    What if there are a hundred civilisations in a galaxy like ours, and 99.9% never attempt colonization? Wouldn't that mean colonization gets attempted in just one galaxy out of ten?
    Out of that hundred, 98 of them are millions of years older than us and half of them a billion years older. Several of them should be 4 billion years older.

    It's just not conceivable to me that civilisations of this age would not be obvious to us if they existed.

    Over these timescales many would've been faced with the death of their star or their planet becoming uninhabitable in other ways. Surely they would not just sit there and take it?

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    Quote Originally Posted by Colin Robinson View Post
    Actually free oxygen can have non-biological explanations, such as water molecules getting broken down by radiation.
    Agreed. Selfsim is also right to point out that this isn't as easy as I made it sound. I'll admit that I'm just excited by the prospect that we could potentially find evidence of life elsewhere sometime in the not-too-distant future. Even if it's a long-ish shot, it's a much shorter shot than hoping for them to show up here.

    Quote Originally Posted by Colin Robinson View Post
    Yes, I think Michael Hart made a calculation like that some years back... But it's one thing to "imagine something that we could probably do if we set our minds to it". It's another thing to actually do it.

    Right now we have one example of radio-capable life, zero examples of interstellar colonization.
    Sure, but we've been radio-capable for only a century or so.

    Quote Originally Posted by Colin Robinson View Post
    What if there are a hundred civilisations in a galaxy like ours, and 99.9% never attempt colonization? Wouldn't that mean colonization gets attempted in just one galaxy out of ten?
    It's possible, but you have to pick pretty small numbers for a lot of terms in the Drake equation to get those kinds of values. Which actually takes us right back to the paper, pointing out that when you account for the high uncertainty in some of the terms, you can get numbers like this or even lower with a reasonably high chance. Many previous analyses of the Drake equation have ended up with numbers of civilizations expected to be in the thousands or even millions, even when adopting what seemed like fairly conservative estimates for most of the terms. Hence the Fermi paradox in the first place.

    I really think it's a pretty decent paper, even if the secondary reporting of it has rather mis-stated its conclusions. You seem to be saying that it's hard to use the Drake equation to estimate the number of civilizations there might be, because everything is very uncertain. What the authors of the paper have done is simply try to quantify and assess exactly that uncertainty to try to get a better handle on it. That seems like a good thing.
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  24. #84
    Actually the Fermi paradox came about before the Drake equation, Fermi was already dead for about 7 years before the drake equation was presented.
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    Quote Originally Posted by The Backroad Astronomer View Post
    Actually the Fermi paradox came about before the Drake equation, Fermi was already dead for about 7 years before the drake equation was presented.
    Sure. But the Drake equation does a pretty good job of quantifying the assumptions that go into the Fermi paradox.
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    Quote Originally Posted by Grey View Post
    Agreed. Selfsim is also right to point out that this isn't as easy as I made it sound. I'll admit that I'm just excited by the prospect that we could potentially find evidence of life elsewhere sometime in the not-too-distant future.
    I can relate to that.

    Even if it's a long-ish shot, it's a much shorter shot than hoping for them to show up here.
    True. But why focus on exo-planets, rather than worlds like Titan, Enceladus and Europa where we can send space probes?

    Sure, but we've been radio-capable for only a century or so.
    Which means it is rash to make assumptions about what a mature radio-capable civilisation would look like or do, surely?

    you have to pick pretty small numbers for a lot of terms in the Drake equation to get those kinds of values.
    No, you only have to pick pretty small numbers for one or two terms. E.g. A lowish value for fi, "the fraction of planets bearing life on which intelligent, civilized life, has developed".

    Which actually takes us right back to the paper, pointing out that when you account for the high uncertainty in some of the terms, you can get numbers like this or even lower with a reasonably high chance. Many previous analyses of the Drake equation have ended up with numbers of civilizations expected to be in the thousands or even millions, even when adopting what seemed like fairly conservative estimates for most of the terms. Hence the Fermi paradox in the first place.

    I really think it's a pretty decent paper, even if the secondary reporting of it has rather mis-stated its conclusions. You seem to be saying that it's hard to use the Drake equation to estimate the number of civilizations there might be, because everything is very uncertain. What the authors of the paper have done is simply try to quantify and assess exactly that uncertainty to try to get a better handle on it. That seems like a good thing.
    What I'm saying is, yes, lots of things are uncertain... but the future of a civilisation like ours is more uncertain than its past. That's the uncertainty which the authors of this paper fail to take seriously, IMO.

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    Quote Originally Posted by Colin Robinson View Post
    True. But why focus on exo-planets, rather than worlds like Titan, Enceladus and Europa where we can send space probes?
    We want to do both, of course!

    Quote Originally Posted by Colin Robinson View Post
    Which means it is rash to make assumptions about what a mature radio-capable civilisation would look like or do, surely?
    Sure. So if you're trying to do a Drake-style analysis of probabilities, it makes sense to assign a pretty high uncertainty to the relevant terms, just as the authors have done.

    Quote Originally Posted by Colin Robinson View Post
    What I'm saying is, yes, lots of things are uncertain... but the future of a civilisation like ours is more uncertain than its past. That's the uncertainty which the authors of this paper fail to take seriously, IMO.
    I disagree. The authors spend an entire section discussing the high level of uncertainty in trying to assign a value to both fl and fi. They end up assigning 200 orders of magnitude of uncertainty to fl and a range of 0.001 to 1 (based on literature and other scientist's estimates) to fi, with fl representing the fraction of planets with "evolutionary competent" life, rather than any sort of life. They also discuss in a supplement the possibility of doing the split differently, so that fl represents the chance of any life at all, so the range of values of fl is smaller, but then fi has correspondingly greater uncertainty. If anything, they've probably overestimated the likelihood of radio-communicating life, and yet still come up with not having any close enough to detect being a sufficiently probably outcome that it shouldn't be surprising.
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    Quote Originally Posted by Grey View Post
    Sure. So if you're trying to do a Drake-style analysis of probabilities, it makes sense to assign a pretty high uncertainty to the relevant terms, just as the authors have done.
    The authors assign high uncertainty to the emergence of technological intelligence, but not to what happens after it emerges. Let me quote from the paper itself:

    "... the default guess should hence be that the low-probability term is likely in the past (fl) rather than the future (fc, L)." (emphasis added)

    In other words, they think the past may well be a fluke, but the future is more predictable...

    Do we really know more about the future than the past?
    Last edited by Colin Robinson; 2018-Jul-13 at 02:43 AM.

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    Quote Originally Posted by Colin Robinson View Post
    The authors assign high uncertainty to the emergence of technological intelligence, but not to what happens after it emerges. Let me quote from the paper itself:

    "... the default guess should hence be that the low-probability term is likely in the past (fl) rather than the future (fc, L)." (emphasis added)

    In other words, they think the past may well be a fluke, but the future is more predictable...

    Do we really know more about the future than the past?
    Fair enough. Earlier in their paper, they do mentioned that their range for fc of two orders of magnitude is based on other people's range of estimates, and they do comment that "it is clear a broader range is intended". But really, if they're overestimating the value of fc, that just means that it's even less likely than the numbers that they suggest that there would be a communicating intelligent species close enough for us to detect.
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