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Thread: expert says aliens dont exist

  1. #31
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    Quote Originally Posted by Colin Robinson View Post
    That depends what you call an "alien".

    Really?....that's your non-answer...semantics???


    Nice dodge...you completely ignored the irrelevance of your comparison.
    The facts, gentlemen, and nothing but the facts, for careful eyes are narrowly watching. Isaac Asimov

  2. #32
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    Quote Originally Posted by R.A.F. View Post
    Really?....that's your non-answer...semantics???

    Nice dodge...you completely ignored the irrelevance of your comparison.
    Semantics is the study of what words mean...

    Are you saying that the meaning of a word like "alien" is irrelevant to this thread?

  3. #33
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    Quote Originally Posted by Colin Robinson View Post
    That depends what you call an "alien".

    If you mean a living thing from one world visiting another, then the Apollo astronauts who walked on the Moon were "aliens" while they were there.
    ...
    Semantics is the study of what words mean...

    Are you saying that the meaning of a word like "alien" is irrelevant to this thread?
    C'mon Colin … you were using an Apollo astronaut as an example of an alien!!!

    I think most here know the difference between semantics word-play (like: 'Apollo astronaut= alien') and an exo-lifeform 'alien'!??

    RAF wasn't implying anything!

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    Quote Originally Posted by Selfsim View Post
    C'mon Colin you were using an Apollo astronaut as an example of an alien!!!
    As an example of a life-form from one world visiting another world. Yes.

    I think most here know the difference between semantics word-play (like: 'Apollo astronaut= alien') and an exo-lifeform 'alien'!??
    Terms like "exo-lifeform", "ET", "extraterrestrial" are based on a conceptual division of the Earth from the rest of the universe the pre-Copernican distinction between what is terrestrial and what is celestial.

    Yesterday, Selfsim, you made the following statement...

    Quote Originally Posted by Selfsim View Post
    There's no credible evidence that aliens exist elsewhere, as well.
    It is true that we don't yet have conclusive evidence of life on worlds that we haven't yet explored at all thoroughly for life. And only a life-form from one of those unexplored worlds would count as "an exo-lifeform 'alien' ".

    On the other hand, the only planet we have explored thoroughly for life, turns out to have living things all over it.

    Generalizing from a sample size of one is not the best way to draw conclusions about life in the universe. But it has to be better than forgetting about the one and only case study we have.

  5. #35
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    I think it's actually quite easy to use suitably tentative language to cover all bases accurately:

    Based on our substantial but far from complete knowledge and understanding of biological processes and planetary formation and development, it seems very likely that life has arisen elsewhere in the universe. However, given that we do not at this point have a full understanding of how non-living chemicals give rise to life, the claim that extraterrestrial life exists remains an extraordinary one.

    Given our understanding of the scale of the universe, the difficulties of space travel, and the inability of people to keep secrets, it seems extremely unlikely that aliens are currently visiting Earth. There is no evidence that aliens visited Earth in the past; this does not rule out the possibility that it has happened at some point, but such a claim would be another extraordinary one.

    I think I understand Colin's point. It may be true to say, "We don't know!" but our ignorance is much more educated than it was; saying "We don't know!" for decade after decade suggests we haven't learnt anything new. Unfortunately we find we have to still say it because people keep making extraordinary claims.

  6. #36
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    Quote Originally Posted by Paul Beardsley View Post
    I think it's actually quite easy to use suitably tentative language to cover all bases accurately:
    I appreciate your effort to cover all bases, Paul.

    Based on our substantial but far from complete knowledge and understanding of biological processes and planetary formation and development, it seems very likely that life has arisen elsewhere in the universe.
    Yes!

    However, given that we do not at this point have a full understanding of how non-living chemicals give rise to life, the claim that extraterrestrial life exists remains an extraordinary one.

    Given our understanding of the scale of the universe, the difficulties of space travel, and the inability of people to keep secrets, it seems extremely unlikely that aliens are currently visiting Earth. There is no evidence that aliens visited Earth in the past; this does not rule out the possibility that it has happened at some point, but such a claim would be another extraordinary one.
    I'd add that if Earth has ever been visited by creatures from another world, microbes from ancient Mars, riding space rocks, are more likely than beings in hi-tech space craft from another star system.

    I think I understand Colin's point. It may be true to say, "We don't know!" but our ignorance is much more educated than it was; saying "We don't know!" for decade after decade suggests we haven't learnt anything new. Unfortunately we find we have to still say it because people keep making extraordinary claims.
    What about the words in the title of this thread (from the headline of the article quoted) "aliens don't exist"? Do they also constitute an extraordinary claim?

    I think they do, because (taken literally) they claim that Earth, as an abode of life, is unique in the universe.

  7. #37
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    Quote Originally Posted by Colin Robinson View Post
    What about the words in the title of this thread (from the headline of the article quoted) "aliens don't exist"? Do they also constitute an extraordinary claim?

    I think they do, because (taken literally) they claim that Earth, as an abode of life, is unique in the universe.
    Yes, of course. It is asserting a conclusion that is not supported by evidence. If anything it is worse than saying, say, "There is definitely life at Tau Ceti," because at least that statement could, in principle, be confirmed or disproven.

    But the (perceived) readership of The Sun is not interested in considered statements of probability. It wants alien invaders or a scarily empty universe.

  8. #38
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    Quote Originally Posted by Colin Robinson View Post
    Are you saying that the meaning of a word like "alien" is irrelevant to this thread?
    So you like playing word games, eh?


    Are YOU saying that you can not rationally address my post regarding your irrelevant comparison of "known to exist" spiders, with "not known to exist" space aliens, without playing word games??


    What?...you don't like it when someone "puts words" in your mouth??...well, guess what? neither do I.


    Now if you would like to try again, and come up with a comparison that doesn't involve "things that we know exist", then be my guest.
    The facts, gentlemen, and nothing but the facts, for careful eyes are narrowly watching. Isaac Asimov

  9. #39
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    Quote Originally Posted by R.A.F. View Post
    So you like playing word games, eh?
    I like considering and discussing the meaning of the terms we use. Yes.

    Are YOU saying that you can not rationally address my post regarding your irrelevant comparison of "known to exist" spiders, with "not known to exist" space aliens, without playing word games??
    The word "space" in your term "space aliens" means what?

    Is the surface of a planet a place in space? Or does "space" just mean the space between planets?

    Or does "space" mean anywhere except Earth? If so, why is Earth conceptually bracketed off from "space"?

    What?...you don't like it when someone "puts words" in your mouth??...well, guess what? neither do I.
    You don't like it when people raise questions about your arguments?

    Now if you would like to try again, and come up with a comparison that doesn't involve "things that we know exist", then be my guest.
    Thank you... We know spiders exist. We don't know whether any particular basement has spiders until we go down into the basement and have a look. We know life exists in the universe. We won't know whether (for instance) Europa has life without close-up investigation using space probes.

  10. #40
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    Quote Originally Posted by Colin Robinson View Post
    The word "space" in your term "space aliens" means what?

    Is the surface of a planet a place in space? Or does "space" just mean the space between planets?

    Or does "space" mean anywhere except Earth? If so, why is Earth conceptually bracketed off from "space"?

    I don't respond well to "what is is" type of responses....particularly when used to avoid "troublesome" realities.



    You don't like it when people raise questions about your arguments?

    What argument? I was simply pointing out the obvious...that your comparison was irrelevant to this discussion.

    Why are you having such "difficulity" admitting that?



    We know spiders exist. We don't know whether any particular basement has spiders until we go down into the basement and have a look.
    Irrelevant to this discussion.



    We know life exists in the universe.
    Yes....as "we" are part of the Universe...what we don't know is if life exist elsewhere. Meaning that your "comparison" using spiders is irrelevant.
    The facts, gentlemen, and nothing but the facts, for careful eyes are narrowly watching. Isaac Asimov

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    Quote Originally Posted by R.A.F. View Post
    What argument? I was simply pointing out the obvious...that your comparison was irrelevant to this discussion.

    Why are you having such "difficulity" admitting that?
    What seems "obvious" to you may not seem obvious to others.

    That is one reason discussions like this happen...

  12. #42
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    Quote Originally Posted by Paul Beardsley
    Yes, of course. It is asserting a conclusion that is not supported by evidence. If anything it is worse than saying, say, "There is definitely life at Tau Ceti," because at least that statement could, in principle, be confirmed or disproven.
    How can this statement be proven or disproven in practice?

  13. #43
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    Quote Originally Posted by Colin Robinson View Post
    What seems "obvious" to you may not seem obvious to others.
    It isn't a matter of opinion...either your comparison is relevant, or it is not...
    The facts, gentlemen, and nothing but the facts, for careful eyes are narrowly watching. Isaac Asimov

  14. #44
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    Quote Originally Posted by R.A.F. View Post
    It isn't a matter of opinion...either your comparison is relevant, or it is not...
    Lets backtrack a little. My point about the spiders was in response to Paul Wally's point...

    Quote Originally Posted by Paul Wally View Post
    Correct, but it's usually the inferences drawn from lack of evidence that tend to become problematic, e.g. the fallacy that absence of evidence is evidence of absence.
    Would you like to tell us what you think about that point, RAF?

  15. #45
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    Quote Originally Posted by Colin Robinson View Post
    Lets backtrack a little.
    Nope...not interested in changing the subject. I've made my point. If any posters (besides you, of course ) want to contest that point, then I'll be back to discuss that, otherwise, I'm out of this thread.
    The facts, gentlemen, and nothing but the facts, for careful eyes are narrowly watching. Isaac Asimov

  16. #46
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    Quote Originally Posted by Colin Robinson View Post
    That depends what you call an "alien".
    Quote Originally Posted by R.A.F. View Post
    So you like playing word games, eh?
    Both of you knock it off.

    Colin Robinson, you are playing word games. We all know what it meant by "alien" in the context of this tread, and your semantics discussion is a complete derailment.

    R.A.F., you are just being needlessly aggressive and argumentative. Frankly, I think you like to pick fights with anyone who shows even a hint of a non-mainstream idea.

    You want to discuss the linked article - then do say. Now knock off the rest of this nonsense.
    At night the stars put on a show for free (Carole King)

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  17. #47
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    Quote Originally Posted by Selfsim View Post
    How can this statement be proven or disproven in practice?
    By travelling to Tau Ceti and taking a look. I didn't say it would be easy but it is at least conceivable, hence "in principle". OTOH if someone said there was no other life anywhere else in the universe, it would not be possible to prove the statement correct, even in principle, though it might be possible to prove it wrong.

    The spider analogy is quite useful here. Just as the presence of cobwebs indicate that spiders are likely to be present, so too the presence of free oxygen in a planet's atmosphere would indicate that life-as-we-know-it is likely to be present. Whereas the absence of free oxygen, like the absence of cobwebs, indicates that the life form is unlikely to be present.

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    Quote Originally Posted by Paul Beardsley View Post
    By travelling to Tau Ceti and taking a look. I didn't say it would be easy but it is at least conceivable, hence "in principle". OTOH if someone said there was no other life anywhere else in the universe, it would not be possible to prove the statement correct, even in principle, though it might be possible to prove it wrong.

    The spider analogy is quite useful here. Just as the presence of cobwebs indicate that spiders are likely to be present, so too the presence of free oxygen in a planet's atmosphere would indicate that life-as-we-know-it is likely to be present. Whereas the absence of free oxygen, like the absence of cobwebs, indicates that the life form is unlikely to be present.
    I'm glad that someone finds my spider analogy useful!

    What you say about oxygen may be right if you're thinking in terms of complex life. If life-as-we-know-it includes anaerobic microbes, Earth itself seems to have already had those for about one billion years before substantial amount of free oxygen started to appear in the Great Oxygenation Event.

  19. #49
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    Quote Originally Posted by Colin Robinson View Post
    What you say about oxygen may be right if you're thinking in terms of complex life. If life-as-we-know-it includes anaerobic microbes, Earth itself seems to have already had those for about one billion years before substantial amount of free oxygen started to appear in the Great Oxygenation Event.
    Yes indeed, but I was talking about evidence, not proof. Similarly, the cobwebs in your cellar might have been made by spiders which have since departed; conversely, the absence of cobwebs does not rule out wolf spiders, trapdoor spiders and tarantulas.

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    Quote Originally Posted by Paul Beardsley View Post
    By travelling to Tau Ceti and taking a look. I didn't say it would be easy but it is at least conceivable, hence "in principle".
    Yep .. and "in practice" it is not conceivable as well, eh?
    (The reason being that it is not presently practical to travel to Tau Ceti to conduct the tests, nor is it presently practical to transmit results back. In fact, the tests may not be able to be designed so as to eliminate false positives or false negatives, either .. depending on metabolism (if any) .. which is 'unknown' in advance of the testing).

    The OP link talks about inferences between UFO sightings and aliens. I can't see much difference between this and our undemonstrated, believed abilities to remotely sense alien life over light year distances ..?? I mean .. we've sent life sensing tests to Mars, and still returned nothing conclusive, so where is the evidence that we can conclusively eliminate all other possible sources of supposed exo-'life signs' (like UFO sightings ≠ (necessarily) alien sightings)?
    Quote Originally Posted by Paul Beardsley
    OTOH if someone said there was no other life anywhere else in the universe, it would not be possible to prove the statement correct, even in principle, though it might be possible to prove it wrong.
    Which would be just about the same as saying: "life is rare and there is other life elsewhere in the universe" because it is also not possible to disprove it.

    Quote Originally Posted by Paul Beardsley
    The spider analogy is quite useful here. Just as the presence of cobwebs indicate that spiders are likely to be present, so too the presence of free oxygen in a planet's atmosphere would indicate that life-as-we-know-it is likely to be present.
    Whereas the absence of free oxygen, like the absence of cobwebs, indicates that the life form is unlikely to be present.
    So, Mars has free oxygen, Ganymede does, Europa has dissolved (free) Oxygen (model based), the rings of Saturn do, Abell 30 does, etc .. Therefore, life-as-we-know-it is likely to be present there?
    (I realise you did reference a 'planet's' atmosphere .. so you may not agree with the moons and the latter two, however, at the moment I can't see much difference 'in principle' .. ie: as far as the point goes ..(??))

    If life-as-we-know-it is not found in these locations, (particularly in the case of Mars), then the generalised statement is falsified, and thus the presence of free oxygen in a planet's atmosphere would not indicate that life-as-we-know-it, is likely to be present(??)

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    Quote Originally Posted by Selfsim View Post
    Nah ... the real problem is when folks succumb to the temptation of incessantly dwelling on speculative discussions, which then conjure up inferences about the 'likelihood' or 'prevalence' of exo-life throughout the obs. universe. (Which then, for some strange, inexplicable reason, seems to then reduce to 'rareness' of certain lifeforms, or rareness of remotely detectable 'bio-signs'... ie: the Fermi paradox, and the ensuing counter 'explanations' for the apparent lack of remnants, or present evidence).
    You should perhaps investigate why other people engaging in what you call "speculative discussion" is a problem to you. How does their speculation become your problem?

    Anyway, there are different kinds of likelihood statements. One is an absolute likelihood statement which asserts a likelihood based on subjective intuition. That's just people expressing their opinion on the matter, and it doesn't bother me much, why should it? Since it's just their opinion based on some intuition they may have, there's no point in arguing because there's no data either way that could decide one way or the other.

    There is however a different kind of likelihood statement based on pure mathematical reasoning, and that is a conditional probability statement. Conditional probability means that if some conditions hold true then the probability follows logically. For example we could say if there are a million civilizations like us in the galaxy with an equiprobable distribution over the 200billion stars then that would be 1 star in every 200 000. We could then proceed to make calculations like the average distance between civilizations, and from that we could then do interesting comparisons like comparing how far radio signals of some power level could travel in comparison to the average distances, or how much power a radio signal must have at the transmitter end in order to be detectable over the aforementioned average distance. It gets more complicated, but it's for instance possible to calculate the probability of detecting a radio signal of some power level (with current SETI technology), from a random star, if there are a million civilizations transmitting at that power level.

    The Drake equation defines a space of possibilities and therefore provides a framework for formulating different conditional probabilities, but it's not an empirical equation that tells us anything about what the actual state of affairs is. Included is every possibility, from zero life in the galaxy to an intelligent civilization in every solar system. The truth is somewhere in that finite space of possibilities.

    With regard to the Fermi paradox, the above-mentioned kind of calculations could be used to work out upper bounds on the number of civilizations with radio communications of a certain power level. For example what is the largest number of civilizations that could exist such that SETI still couldn't detect them with sufficient probability. Or we could work out a lower bound. What is the least number of civilizations such that we should have detected a signal by now. These calculations would also be conditional on the radio power level and that they are using radio at all etc. They could be using subspace transmissions, but that would be an example of speculation.

  22. #52
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    Quote Originally Posted by R.A.F. View Post
    If any posters want to contest that point, then I'll be back to discuss that
    Per this post, I will now continue...


    Quote Originally Posted by Paul Beardsley View Post
    The spider analogy is quite useful here.
    It begins from a flawed premise....that spiders and aliens both exist...we do have conclusive proof of one, but not the other.


    Lets see if I can make it any clearer...allow me to substitute a few words from your own post...

    Just as the presence of cobwebs indicate that (something that we KNOW exists) are likely to be present, so too the presence of free oxygen in a planet's atmosphere would indicate that (something we DON'T know exists) is likely to be present.

    See what I'm saying?....if not, please explain why not.
    The facts, gentlemen, and nothing but the facts, for careful eyes are narrowly watching. Isaac Asimov

  23. #53
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    Quote Originally Posted by Paul Wally View Post
    Conditional probability means

    The truth is somewhere in that finite space of possibilities.
    ...
    calculations could be used to work out upper {and lower} bounds ...
    ...
    Statistics don't reveal 'truths'. Even a likely outcome is not a dead certainty.

    Of all the UFO sightings here on Earth, you think we could calculate the upper and lower bounds constraining the likelihood that one, or some of them, contained aliens, eh?

    Statistical 'calculations' with no evidence basis, merely serve to obfuscate reality and support fixed beliefs ... which it seems, is precisely where over-speculation which trivialises the lack of initial evidence, may have led in this instance.

    The OP's linked article by UFO investigation expert David Clarke, makes the point that evidence is the only thing which matters, and en-masse technology to date, has actually disproven the alien activity idea. Statistical calculations are irrelevant to this argument.

    Quote Originally Posted by Paul Wally
    but that would be an example of speculation.
    .. and the rest of your calculations wouldn't be, eh?

  24. #54
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    Quote Originally Posted by Colin Robinson View Post
    What about the words in the title of this thread (from the headline of the article quoted) "aliens don't exist"? Do they also constitute an extraordinary claim?
    It certainly would be an extraordinary claim, and in fact I made that very point in my first post in this thread. I don't think that's really what the headline writer was trying to say though, I think it's just poorly worded.
    As above, so below

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    Quote Originally Posted by Paul Beardsley View Post
    Yes, of course. It is asserting a conclusion that is not supported by evidence. If anything it is worse than saying, say, "There is definitely life at Tau Ceti," because at least that statement could, in principle, be confirmed or disproven.
    This is a bit of a nitpick, but I think that's not quite correct. It could in principle be confirmed, but not disproven, because there would always be the chance that life exists in some form that we can't detect.
    As above, so below

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    Quote Originally Posted by Jens View Post
    This is a bit of a nitpick, but I think that's not quite correct. It could in principle be confirmed, but not disproven, because there would always be the chance that life exists in some form that we can't detect.
    I was envisaging either a planet teeming with life, or a rocky, moonlike world (or no world at all) with nothing in between, but yes, you're right.

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    Quote Originally Posted by Selfsim View Post
    Statistics don't reveal 'truths'. Even a likely outcome is not a dead certainty.
    Depends on what you mean by 'statistics', empirically gather data points or mathematical probability theory. I was referring to the latter, which does reference intrinsic truths of probability. And a likely outcome is exactly what it says, a likely outcome. In probability theory the likelihhood of the outcome is the certainty. If there really is a 50% chance then it is certain that it is a 50% chance.

    Of all the UFO sightings here on Earth, you think we could calculate the upper and lower bounds constraining the likelihood that one, or some of them, contained aliens, eh?
    Well, we don't even know whether many of those UFO sightings were sightings of actual containers, not to mention containers of aliens. It's completely different case from calculating probabilities from what we know about propagation of radio waves through space.

    Statistical 'calculations' with no evidence basis, merely serve to obfuscate reality and support fixed beliefs ... which it seems, is precisely where over-speculation which trivialises the lack of initial evidence, may have led in this instance.
    This looks like bunch of sweeping generalizations to "obfuscate reality" for yourself. What specifically are you referring to?


    .. and the rest of your calculations wouldn't be, eh?
    I guess not. Are radio waves speculative?

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    Paul;
    Are you saying anything of relevance to the thread topic? (If so, I apologise in advance. I must have missed it) ...
    Quote Originally Posted by Paul Wally
    Conditional probability means that if some conditions hold true …{etc}
    … And the conditional probability statement says nothing about the veracity of that assumption, so why are we even discussing this?

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    Quote Originally Posted by R.A.F. View Post
    Since there is no evidence, the default answer MUST be no alien visitors.


    ...or do you disagree?
    I disagree.
    "We don't know" is the only, and default, answer we have, RAF. True skepticism is withholding judgment in the face of insufficient evidence.
    Where the telescope ends, the microscope begins. Which of the two has the greater view?

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    Quote Originally Posted by R.A.F. View Post
    That makes the assumption that the 2 ideas, (that aliens have visited, or that aliens have not visited), are somehow equally likely...they are not.
    I'm interested in hearing how you quantified the 2 ideas, so that we know which is more likely.
    Where the telescope ends, the microscope begins. Which of the two has the greater view?

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