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Logical Positivism versus Cosmology

  1. Apr 20, 2008 #1


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    When I went through a course on Relativity, the professor said that relativity was at its foundation based on the philosophy of logical positivism (i.e., the only meaningful discussion is of observations, no discussion of a larger reality is meaningful), which seems to preclude larger discussions of cosmology. I also understand that Logical Positivism was the leading philosophy of science until the 1980s, but after that Realism became the more accepted philosophy of science.

    It seems like some of the contradictions of relativity and quantum mechanics could be explained if we took a realist interpretation of the formula (that they correctly predict measurements, but are from only a limited perspective of a external reality). Of course we would be reopening the questions of why the measured constant speed of light is always measured the same and Bell's experiments. But would that be less acceptable than to accept the contradictions implicit in the logical positivist interpretations of Relativity (like the twin paradox) and Quantum Mechanics (like Schroedinger's Cat)?

    So, in discussions of cosmology, shouldn't we be working to remove any logical positivist assumptions from our discussions? Specifically, isn't the changing of time and space a logical positivist concept (those concepts would be valid when predicting measurements, but not when discussing overall cosmology). And isn't the Copenhagen interpretation of quantum mechanics (that the world is probabilistic in reality) a logical positivist concept as well?

    Time and space seem like abstract human concepts which use clocks (uniformly repeating phenomena) and rulers (uniformly spaced phenomenon) to compare with other phenomena. I can see how rulers and clocks can be affected by the world, but it seems like the concepts of time and space should not be entangled with specific clocks and rulers in discussions of cosmology.

    And even if our measurements of small phenomena give us a probabilistic answer, isn't that a limitation of our measures rather than an actual view of the world itself? Or alternatively, are we measuring the probability of a particular event occurring rather than proving that reality is, in and of itself, probabilistic?

    Maybe I am missing something here, but I can't think of what it is. Maybe the constant speed of light and Bell's experiments are so compelling that we just have to accept the contradictions, but I am not convinced. Am I off track and missing something here? Is there other evidence that I am not considering?
  2. jcsd
  3. Apr 20, 2008 #2


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    The mystics and the para people are investigating the universe from their point of view. (Philosophy)
    The Cosmologist, who have some evidence based upon the interpretations of the observations and calculations of the astronomers, are doing their investigations. (This forum, Astronomy & Cosmology)
    The phenomenologist are looking at the experimental information produced by the physicists. (Beyond the standard model)

    Yup! There are a lot of unanswered questions.

    These forums are divided into different areas of interest with a lot of overlap.
    Where you want this discussion to go will determine where the moderators move this thread so that you will get the most input to the conversation.
  4. Apr 20, 2008 #3
    The philosophical weight we give to what a measurement is has nothing to do with the facts of the measurements themselves. So no, changing of time and space is NOT a logical positivist concept, it was simply a success of the approach. The essential purpose of logical positivism was to remove unmeasurables from the domain of physics. Even if we allow these unmeasurables back in they MUST remain consistent with what we do measure. By throwing out logical positivism we cannot throw out the fact that the measurables do in fact define the only things we can actually know.

    I've never been a pure logical positivist but you seem to conflate the empirical content with theoretical philosophy. Even under a complete rejection of logical positivism we can't drop the empirical content when talking about the "overall" anything in science.
  5. Apr 20, 2008 #4
    I disagree completely with that observation.

    GR can demonstrate many things about "a larger reality" such as spacetime topology, open and close universes, expansion etc. Actually spacetime as a whole is exactly that larger reality under which observer dependent measurements in terms of time and space are encompassed.
  6. Apr 26, 2008 #5


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    Thanks. Basically, I'm thinking this discussion would eventually go like this (but probably in three seperate questions):

    1. Can anyone show that Relativity and Quantum Mechanics are not still based on Logical Positivism? If Relativity and Quantum Mechanics are based on logical positivism, then for cosmology questions, it would seem there must be another underlying mechanism (much like Ptolemy's formulas work well but were based on human perspective from earth and there was a different underlying reality that was only pointed to by new, hard to find evidence that didn't fit his formulas).
    2. Then I would want ask for a list of contradictions and evidence that didn't seem to fit current theories.
    3. Then I would want to ask for a list all the logically possible alternative theories. If the the current theories don't actually describe reality, then the answer must be in some almost universally accepted assumption, otherwise we would have found it sooner...

    That may mean going from Cosmology (is the evidence currently interpreted correctly) to phenomenology (looking at the specific evidence) to Philosophy (looking more broadly, guessing to find frameworks that are consistent with all the evidence).

    Do you think this first question would get more response in one of the other two forums? If so, the moderators can feel free to move this to another forum is they think this first question would be better somewhere else (Or if I need to repost, please let me know).
  7. Apr 26, 2008 #6


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    I agree that any discussion of reality has to be an attempt to look at all the observable evidence and argue towards the best explanation. What I am thinking is that it seems like we may be getting our perceptions of the limitations of our tools/perspective intermixed with our perception of reality (like Ptolemy did). That would be like if the only way we were able to look outside was through a foggy window then we might think the world outside was always foggy. I agree that until measurements were obtained that might point to a foggy window and clear world, that discussion would be in the realm of philosophy rather than science.

    So, yes, my next question will be to try to find or work up a list of things that do not seem to fit current theories and then try to see if anything else might fit the observations. I have done some looking already but I can't seem to find any other theory that fully makes sense to me yet, yet I don't want to accept current theories, and their apparent logical inconsistencies, only by default.

    I think what I am looking for here is for someone to be able to say something like "Relativity seems similar to Ptolemy's formulas in that they are based on the perspective of the observer, but they are really different because..."

    If I could get that question answered to my satisfaction then that would save me alot of time on a potential wild goose chase...
  8. Apr 26, 2008 #7


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    It seems like the question may concern the definition of "time" and "space". I think I am defining them to mean by definition that they are independent of the observer, whereas I am agreeing that individual measurements via "clocks" and "rulers" could be dependent on the observer as the formulas describe. And if those concepts are seperate, it seems like cosmology is supposed to be observer independent, so the concepts of an indendent space and time would seem to be most appropriate when discussing cosmology. In fact, we can't seem to even talk about an expanding or closed universe without imagining a conceptual coordinate system in which it is expanding into, or which is outside the closed universe. And if time/space are in fact only conceptual frameworks (as I have defined them) rather than something physical, then it seems it can't be argued that they don't actually exist outside a closed or expanding universe and therefore should not be discussed.

    Just as there is an independent concept of speed on the highway that is independent of the cars, yet each car has a speedometer that may register a slightly different speed.

    If time and space are changed by the perspective/speed of the observer, there seems some logical contradictions, such a the twin paradox and Shrodinger's Cat. Do those thought experiments actually make sense? If not, is there a reason why I should consider those thought experiments as actually describing reality?

    I know that people have looked and haven't found any convincing alternatives, but if the choice is between accepting paradoxes and endlessly searching for a better answer that fits all the evidence, then I think I would opt to do the search, however unlikely it may be to find a better answer (highly unlikely is better than accepting a logically impossible paradox).
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