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Thread: Evidence for ET is mounting daily, but not proven.

  1. #31
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    Quote Originally Posted by astromark View Post
    As was said, but you missed... NO. is the answer we have.
    The fact that none of us like that answer does not change it...
    Probability is not proof. We have not a single case of life having shown to be any place but here on planet Earth.
    Yet still we speculate... and look even harder. No. is just not acceptable is it ?
    And what is the question? Is there life beyond Earth in the universe? The answer to that is not "No", but nobody knows.
    Is the question is there proof there is life beyond Earth? The answer to that is currently no. But that doesn't mean such proof will never arrive.

    Bob Clark

  2. #32
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    Quote Originally Posted by djellison View Post
    I think the title of this thread is misleading. There is, to date, no evidence for ET whatsoever. None. Zero. There are various areas of study that might give us cause to suspect that we can extrapolate certain variables across the known universe and infer that there might or indeed should be life elsewhere - but that's not evidence, that's conjecture.
    I disagree. While the evidence is still circumstantial, it is certainly now above zero.

    from July 2005, a predicted observation:
    If bacteria are consuming complex hydrocarbons at the surface of Titan, the observable effects might include: complete consumption of C2H2 at the surface, reduction in C2H6 and organic solids at the surface compared to the accumulation expected from photolysis alone, and a sink of hydrogen at the surface creating a gradient in the hydrogen mixing ratio with altitude.
    from June 2010
    Recent results from the Cassini mission suggest that hydrogen and acetylene are depleted at the surface of Titan. Both results are still preliminary and the hydrogen loss in particular is the result of a computer calculation, and not a direct measurement.

  3. #33
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    Quote Originally Posted by baric View Post
    I disagree. While the evidence is still circumstantial, it is certainly now above zero.

    from July 2005, a predicted observation:


    from June 2010
    This doesn't rise to anything I would qualify as even circumstantial.

  4. #34
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    Quote Originally Posted by Trakar View Post
    This doesn't rise to anything I would qualify as even circumstantial.

    "Circumstantial evidence is evidence in which an inference is required to connect it to a conclusion of fact"

    No inference is required to connect the two quotes I provided. They actually represent direct evidence. The only question is the reliability of the observations and the possibility of a non-biological explanation. In other words, they do not rise to anything that we would qualify as conclusive. Maybe that's the word you were looking for?

  5. #35
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    Quote Originally Posted by baric View Post
    "Circumstantial evidence is evidence in which an inference is required to connect it to a conclusion of fact"

    No inference is required to connect the two quotes I provided. They actually represent direct evidence. The only question is the reliability of the observations and the possibility of a non-biological explanation. In other words, they do not rise to anything that we would qualify as conclusive. Maybe that's the word you were looking for?
    The first quote speculates a prediction, about one potential sign for a type of life never before witnessed (cryo-methanogenic life). This is not an exclusive indicator (as in the only possible explanation for the conditions speculated about would definitely be this never before witnessed form of life that exists in liquid methane with a metabolism never evidenced).

    The second quote concerns no direct measurements, but rather looks at calculations concerning some aspects data recovered by the Titan probe and concludes that one interpretation of this may be that there is less of certain compounds on the surface of Titan than some scientists had predicted prior to ever having any solid information about conditions at Titan's surface.

    As I said, nothing I would even qualify as circumstantial.
    To me, this is like having a neighbor telling you that they thought they saw a set of depressions in their back yard and you concluding that they may well signify dragon footprints.

  6. #36
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    Let us look at the facts we know... and then argue the validity of any information.
    Many exo-solar planets have been found., and are being found.
    Our equipment does not yet let us see the Earth like planets we seek.
    That a greater number of planets are smaller than the gas giants is a well reasoned case.
    BUT... still we have not found. and do not like not knowing... are we alone ?
    The OP suggests that the case for ET discovery is getting higher... or closer.
    I would argue that we might be better to stop looking. Learn to be quiet. and keep our heads down.
    I would like to establish what is it we are looking for ?

  7. #37
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    Quote Originally Posted by astromark View Post
    Let us look at the facts we know... and then argue the validity of any information.
    Many exo-solar planets have been found., and are being found.
    Our equipment does not yet let us see the Earth like planets we seek.
    That a greater number of planets are smaller than the gas giants is a well reasoned case.
    BUT... still we have not found. and do not like not knowing... are we alone ?
    The OP suggests that the case for ET discovery is getting higher... or closer.
    I would argue that we might be better to stop looking. Learn to be quiet. and keep our heads down.
    I would like to establish what is it we are looking for ?
    I see no reason to quit looking (if any advanced life exists, it is better to know that it exists long before it focusses its attention on us).
    But I'm sure in no hurry to set up a beacon system to announce our existence.

  8. #38
    I agree wit the OP by reversing the question on the ET existence:
    What are the reasons that life does not exist elsewhere in the universe?
    If one is answering this question (I named this answer "ANS")
    Then, you will see that the plausibility of "ANS" will be less strong vs the plausibility of "-ANS"

    As I feel I am not so clear with my poor English, here is a simple/stupid example (only to demonstrate my point, it is not a valid answer):
    ANS=Because [a sun like ours + a planet like ours (regarding size/orbit) + having a big moon] doesn't/can't exists
    -ANS=There is no reason to think that this assemblage doesn't exists in several copies

  9. #39
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    What would be the impact if we were to discover all the processes leading to life on Earth? It seems to me that once the mechanisms are firmly established, it would be hard to deny those processes will take place in compatible conditions elsewhere. Isn't it our lack of a full understanding the evolution from chemistry to biochemistry that is keeping us back from asserting that life is natural and common process?
    For each man, according to the measure of his intelligence, must speak what he can speak, and do what he can do. - Alfred, King of Wessex
    Calm down, have some dip. -George Carlin

  10. #40
    Quote Originally Posted by Hlafordlaes View Post
    ... it would be hard to deny those processes will take place in compatible conditions elsewhere...
    I agree, it is what I have tried to say

  11. #41
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    Quote Originally Posted by Trakar View Post
    To me, this is like having a neighbor telling you that they thought they saw a set of depressions in their back yard and you concluding that they may well signify dragon footprints.
    Except that, in this case, your neighbors are a NASA scientist analyzing measurements taken from the Cassini probe, the dragon is hypothetical microbial life that can create energy by consuming hydrogen and ethane, and the "footprints" are the predicted absence of hydrogen and ethane.

    No one is claiming that this is conclusive evidence or proof of alien life, but to dismiss it as non-evidence by making an analogy with fantasy creatures is absurd, imo.

  12. #42
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    Quote Originally Posted by baric View Post
    No one is claiming that this is conclusive evidence or proof of alien life, but to dismiss it as non-evidence by making an analogy with fantasy creatures is absurd, imo.
    It is NOT evidence for aliens. It is evidence for something else that might, under some interpretations, be a symptom of the existence of aliens, but could very well be something else entirely.

    Again - I repeat - we have NO evidence for the existence of Aliens. None.

    But give that - the only correct answer to the question ' is there life elsewhere in the universe'.. is 'We don't know'.

    One day, we might know.

    Right now, we don't.

  13. #43
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    Quote Originally Posted by Baud View Post
    I agree wit the OP by reversing the question on the ET existence:
    What are the reasons that life does not exist elsewhere in the universe?
    If one is answering this question (I named this answer "ANS")
    Then, you will see that the plausibility of "ANS" will be less strong vs the plausibility of "-ANS"

    As I feel I am not so clear with my poor English, here is a simple/stupid example (only to demonstrate my point, it is not a valid answer):
    ANS=Because [a sun like ours + a planet like ours (regarding size/orbit) + having a big moon] doesn't/can't exists
    -ANS=There is no reason to think that this assemblage doesn't exists in several copies
    If I am understanding you correctly, this is the basic process.
    The problem arises from not knowing exactly how similar to the single example of life generation we know about, conditions need to be to recreate the process.
    If it just requires liquid water and some form of available energy, the universe should be oozing with life nearly everywhere we look.
    If it requires precisely the conditions and sequence of occurences experienced by our bio-history, there may only be a very few and infrequent examples throughout the visible universe.
    I suspect that the answer lies somewhere between these extremes (and perhaps beyond them with regards to life as we don't know it) but until we find some non-terrestrial versions to examine, our data-point of one isn't giving up too many answers.

    While the OP seems to perceive that science is racing outward from a position of scarcity toward a position of abundance, my perceptions are rather the opposite. Science started out with the perception that the abundance of life on Earth was typically representative of the universe as a whole, and we have since been retreating toward the rarity position as we have found the universe to be ever more barren than expected.

  14. #44
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    You might suggest that planets in our solar system is evidence for planets around over stars, but really it is the justification for an extrapolation without evidence. Not until we actually have observations that can only be explained by the presence of planet around other stars do we have actual evidence for the existance of planets, as we now do. We do not have this level of evidence for life. Even the ratio of methane on titan: Can we be sure that the only explanation for this observation is the presence of life? Not only that... we have quite a bit of negative evidence that life is not as ubiquitous, widespread or universal, as we might have once hoped. We also have strong ideas about how life evolves, operates in ecologies, costs of metabolism etc, that indicate the life would not prosper in deep space for example... this leads to constraints in its likely distribution, to say the least. Once decent interferometer spectrographs are pointing at watery planets then perhaps we will see evidence for ET starting to mount, maybe even on a daily basis.

  15. #45
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    Quote Originally Posted by baric View Post
    Except that, in this case, your neighbors are a NASA scientist analyzing measurements taken from the Cassini probe, the dragon is hypothetical microbial life that can create energy by consuming hydrogen and ethane, and the "footprints" are the predicted absence of hydrogen and ethane.

    No one is claiming that this is conclusive evidence or proof of alien life, but to dismiss it as non-evidence by making an analogy with fantasy creatures is absurd, imo.
    Have you an example of a cryo-methanogen life-form to point to?

    sounds rather like a fantasy creature to me.

    oh, and the "footprints" are your interpretation, the neighbor merely qualified them as a set of depressions in his back yard.
    just as the scientists are not looking at direct measurements of hydrogen but rather some circuitous calculations which seem to be indicating lower levels of Hydrogen than some scientists predicted before there was any strong evidence one way or another for conditions and surface composition.

  16. #46
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    Quote Originally Posted by djellison View Post
    It is NOT evidence for aliens. It is evidence for something else that might, under some interpretations, be a symptom of the existence of aliens, but could very well be something else entirely.

    Again - I repeat - we have NO evidence for the existence of Aliens. None.
    If methanogenic life is found on Titan, this data will undoubtedly be touted as part of the overall evidence. Are you suggesting that data and analysis can be considered to be 'evidence' only after it is conclusive?

    I suggest otherwise.

  17. #47
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    Quote Originally Posted by transreality View Post
    ...Once decent interferometer spectrographs are pointing at watery planets then perhaps we will see evidence for ET starting to mount, maybe even on a daily basis.
    Perhaps, or not.
    I'd rather let the evidence lead and guide my considerations than pursue speculations that may unduly filter/distort my considerations of the evidences.
    If it exists, I look forward to its discovery, and the understandings we will gain.

  18. #48
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    Quote Originally Posted by baric View Post
    If methanogenic life is found on Titan, this data will undoubtedly be touted as part of the overall evidence
    Maybe it will be - but right now, it's just an observation.

  19. #49
    Quote Originally Posted by transreality View Post
    You might suggest that planets in our solar system is evidence for planets around over stars, but really it is the justification for an extrapolation without evidence.
    my bold
    (I am not sure you are answering my post, but anyway here it is...)

    I really don't want to extrapolate... I will try again:

    Most of the posts in this thread are about the possible existence of ET life. [yes/no/don't know/...]

    This is half of the questioning, and I agree with most of you when you say that we have no evidences.
    The second half is: What are the arguments that can be used to explain that ET life doesn't exists:

    1)Regarding the OP: day after day, the arguments to explain that life doesn't exists are decreasing (in strongest and in number) because as A.DIM pointed out, we are discovering a greater variety of life on earth (extremophiles, arsenic-using microbe), complex organic founded outside the earth, possible exchanges between planets,etc
    2)I feel that if one is challenged to find an argument that can explain why the life only exists on earth, then this argument will be weaker than the counter-argument
    This is also why I agree with Hlafordlaes when he/she says "What would be the impact if we were to discover all the processes leading to life on Earth? It seems to me that once the mechanisms are firmly established, it would be hard to deny those processes will take place in compatible conditions elsewhere."

  20. #50
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    Quote Originally Posted by djellison View Post
    Maybe it will be - but right now, it's just an observation.
    ok, that's a start. We've all determined that it's an observation.

    Now... it just so happens that this "observation" matches observations predicted if a certain theorized form of methanogenic life existed on Titan. Certainly we can agree upon that as well; after all this tentative "affirmation" created a bit of a stir last summer!

    So I think we can agree that it's not just any random observation like "hey, we are seeing lower-than-expected levels of ethane on the surface of Titan... what could be causing that?"

    And if these anomalous levels had not been detected, I think it's safe to wager that this contrary observation would have been considered evidence AGAINST this theorized life.

  21. #51
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    Quote Originally Posted by Trakar View Post
    Have you an example of a cryo-methanogen life-form to point to?

    sounds rather like a fantasy creature to me.

    oh, and the "footprints" are your interpretation, the neighbor merely qualified them as a set of depressions in his back yard.
    just as the scientists are not looking at direct measurements of hydrogen but rather some circuitous calculations which seem to be indicating lower levels of Hydrogen than some scientists predicted before there was any strong evidence one way or another for conditions and surface composition.
    Sorry I missed this response.

    While it is true that the depletion of hydrogen is calculated from models, the same cannot be said for the depletion of acetylene and ethane at the surface.

    I am treating the predictions and observations at face value. A paper theorized an non-terrestrial form of life and even predicted a series of anomalous observations. Five years later, these predictions were tentatively affirmed.

    If ET life is ever to be found, exactly how would the discovery and verification process begin any differently than this? And does this potentially represent a step closer to discovery, or is it equivalent to having no theory, no predictions and no affirming observations at all?

  22. #52
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    You presume, wrongly, that if something is not evidence against something, it must be evidence for it. This is untrue.

  23. #53
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    Quote Originally Posted by djellison View Post
    You presume, wrongly, that if something is not evidence against something, it must be evidence for it. This is untrue.
    Hmmm... those words taste really funny. I don't think they came out of MY mouth.

  24. #54
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    Quote Originally Posted by baric View Post
    ...If ET life is ever to be found, exactly how would the discovery and verification process begin any differently than this? And does this potentially represent a step closer to discovery, or is it equivalent to having no theory, no predictions and no affirming observations at all?
    I would hope that it starts with the finding of an actual life form that is unique enough to demonstrate a distinct genesis from terrestrial life. Otherwise we're largely taking bits of science and speculation and generating a plausible narrative to explain and connect the two....what I generally think of as science fiction rather than evidence driven science.

    as for the detected levels of acetylene and ethane, we really do not well understand the particular cryo-Titanologic processes at work on Titan's surface with enough confidence to say for certain that such levels are "depleted." All we can really say is that they are a bit lower at some locations than some scientists projected as an average for the general surface when we knew even less.

  25. #55
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    Quote Originally Posted by Trakar View Post
    I would hope that it starts with the finding of an actual life form that is unique enough to demonstrate a distinct genesis from terrestrial life.
    Isn't that jumping the gun just a bit? The search for ET life necessarily begins with the search for chemical markers and disequilibriums.

    as for the detected levels of acetylene and ethane, we really do not well understand the particular cryo-Titanologic processes at work on Titan's surface with enough confidence to say for certain that such levels are "depleted." All we can really say is that they are a bit lower at some locations than some scientists projected as an average for the general surface when we knew even less.
    Of course they can say they are depleted because they are comparing them to models. How else would you know to verify your models? Is ethane condensing at a higher temperature than expected? Is some heretofore unknown chemical process consuming the ethane?

    Some guy at NASA came up with one model of a chemical process to explain it and made the additional prediction about the distribution of H2 in the atmosphere. Someone else independently did an analysis that seemed to corroborate the H2 prediction.

    If this were simply presented as a novel chemical reaction, I doubt seriously that we would be debating the validity of this evidence. But because this particular chemical process was also endowed with the description of "life", all of a sudden it becomes a polarizing topic.

  26. #56
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    Quote Originally Posted by baric View Post
    Isn't that jumping the gun just a bit? The search for ET life necessarily begins with the search for chemical markers and disequilibriums.
    Not at all. Disequilibriums may help you to refine a search but they indicate nothing but an imbalance from what you expected and are wide open to sourcing, causation and implication.

    Of course they can say they are depleted because they are comparing them to models.
    Then it would be more proper to say that the model values are inflated, in which case the first step would be to re-evaluate the models and assumptions with which they were constructed. We aren't trying fit the facts to the models, we are trying to get models to accurately represent the facts.

    I doubt seriously that we would be debating the validity of this evidence. But because this particular chemical process was also endowed with the description of "life", all of a sudden it becomes a polarizing topic.
    Popularized sensationalization is the bane of scientific rigor, but it also helps loosen congressional purse-strings so what are you gonna do?

  27. #57
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    Quote Originally Posted by Trakar View Post
    Then it would be more proper to say that the model values are inflated, in which case the first step would be to re-evaluate the models and assumptions with which they were constructed. We aren't trying fit the facts to the models, we are trying to get models to accurately represent the facts.
    No one is suggesting to fit the observations to the model... that doesn't make any sense! I think we both certainly agree on that. But why is it invalid to theorize about a methanogenic component to the model if it makes a better fit to the observations, and especially if it provides falsifiable predictions?

  28. #58
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    Quote Originally Posted by astromark View Post
    Let us look at the facts we know... and then argue the validity of any information.
    ...
    I would argue that we might be better to stop looking. Learn to be quiet. and keep our heads down.
    Based on what facts, astromark? That our galaxy (universe?) is teeming with advanced ET life, listening and scheming to come take our stuff or enslave us?

    You should be comforted in knowing then, that we are effectively becoming invisible to anyone looking for radio leakage.There is only so much usable bandwidth in the EM spectrum, and more and more less powerful signal strengths are being used so as to accomodate more tech.

    I would like to establish what is it we are looking for ?
    Microbial life is what we'll discover, if anything.
    The odds against SETI type success are slim to none.
    If advanced ET life exists and is to be known, it will be on their terms, I'm afraid.
    Where the telescope ends, the microscope begins. Which of the two has the greater view?

  29. #59
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    Are we not causing disequilibriums in our planetary environment that could be detected by hypothetical ET with fancy space-borne telescopes? Or could it all be explained away as the result of volcanic out-gassing, for example.

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    Quote Originally Posted by transreality View Post
    Are we not causing disequilibriums in our planetary environment that could be detected by hypothetical ET with fancy space-borne telescopes? Or could it all be explained away as the result of volcanic out-gassing, for example.
    The sustained high level of free oxygen is a strong biosignature, probably the most compelling argument for life on our planet from afar.

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