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Multiple universes: Nothing more than philosophising?

  1. Mar 5, 2015 #1
    Why do astronomers talk about multiple universes, that is philosophising - isn't it?
     
  2. jcsd
  3. Mar 5, 2015 #2
    I'm taking your meaning to be "is it pointless" to which the answer is of course not. Predictions don't make themselves and so to progress our understanding, various models need to be fleshed out and made falsifiable, which is only done by researching them. Moreover, I find it ridiculous how negative of a connotation philosophy has amongst some scientists. Without philosophy of science/physics/mathematics, you are just plugging in numbers into equations with zero context and without any real attempts to obtain an understanding.
     
  4. Mar 5, 2015 #3
    It may explain Dark Matter, it may explain why Dark energy's strength is the way it is, it presents ideas and solutions that many find satisfying.
     
  5. Mar 5, 2015 #4

    phinds

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    Basically, yes. Although there are some very serious scientists (Sean Carroll comes to mind) who believe in the multiverse there is absolutely zero evidence to support it and the multiverse theories make no falsifiable predictions. Popper argues that this clearly means such theories are not science but Carroll says we need to rethink the whole business of falsifiability as a test on theories. I admire Carroll but I hope science does not go down that road.
     
  6. Mar 5, 2015 #5
    I agree. It would be a travesty and a huge hit to the credibility of science if we abandoned one of its cornerstones to make some theories more attractive without doing any actual observations.

    Bringing this back to the original question, who is to say that the multiverse theory won't one day be falsifiable with some not-yet-invented piece of equipment? The ancient Greeks and Indians had ideas about atoms, but could never in their wildest dreams have imagined the experiments that would one day prove their existence.
     
  7. Mar 5, 2015 #6

    phinds

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    Well, so far there aren't any predictions that are falsifiable with ANY equipment. The multiverse, as far as I know, is forever causally removed from out universe.

    If/when multiverse theories include falsifiable predictions that becomes a different story.
     
  8. Mar 5, 2015 #7

    Chronos

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    There have been, and will continue to be efforts to devise observational tests of multiverse theories. I haven't seen any yet that appear capable of falsifying the multiverse. It's unclear, at least to me, if that's even possible in principle. Until the need for a multiverse can be empirically demonstrated, I feel it's little more than an exercise in imagination. Science is not just about the possible [that's what math is for], it's about what is necessary.
     
  9. Mar 5, 2015 #8
    I'd actually say, that if someone believes that billions of years ago there was a big bang, it's a matter of well, common sense there would be multiple universes.

    But, myself, I doubt whether there was a big bang. Gut feeling. :-)
     
  10. Mar 5, 2015 #9
    I find it strange that one time and perhaps not long ago intelligent people would say maybe there are other planets around stars with life. Common sense the universe is teeming with planets and life. IMHO.
     
  11. Mar 5, 2015 #10
    Yes, the strongest reason I've heard is that there are too many variables with just the precise value to make it likely that our universe could exist (but not impossible!). The multiverse hypothesis says that many of the possible universes have popped into existence, and so our 'improbable' universe becomes probable because it is just one of many, equally probable universes that exists.
     
  12. Mar 5, 2015 #11

    Drakkith

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    The big bang was not an event, it is a process describing the evolution of the universe from its high density and temperature state to the current low density and low temperature state. In that sense I see no reason to believe in other universes.
     
  13. Mar 5, 2015 #12

    Drakkith

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    This assumes that the laws in our universe just happen to be as they are because of pure chance. It's possible they simply couldn't be any other way.
     
  14. Mar 5, 2015 #13

    Chronos

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    I view that as one of the worst possible explanations for the values of natural constants. It's pretty obvious, at least to me, the laws of physics are not fine tuned for our existence, we are fine tuned for existence compatible with the laws of physics.
     
  15. Mar 6, 2015 #14

    OCR

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    I agree, and it's a damn shame!... :oldgrumpy:
     
  16. Mar 6, 2015 #15

    Chronos

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    I think much of the philosophy backlash in the science community is driven by leaps of logic that often prove flawed, and sometimes patently naive after the facts become known. I agree this is regrettable to some extent. Many of histories finest scientists had strong philosophical leanings that led them to spectacular discoveries - e.g., Einstein. On the other hand, intuition, however reasonable, must still be vetted scientifically. Science without philosophy is like the three blind men describing an elephant. It's a necessary evil if we aspire to stitch the quilt together. Academia still awards the title Doctor of Philosophy to qualified seamstresses.
     
  17. Mar 8, 2015 #16

    If we were to follow rigidly the falsificationist account of what is science then it's metaphysics. But then we should include in the same category superstring theory and so on. Personally I think things are much more complex.

    There is an interesting article in Scientific American Special Edition 2014 'Secrets of the Universe' ('Does the Multiverse really exist?', you can also read it here: http://www.relativitycalculator.com/articles/multiverse_exist_george_ellis/page_38.html ).

    Personally I agree with the main conclusion of the author, indeed currently there is no conclusive evidence for the multiverse (which to establish the concept as part of accepted scientific knowledge) but at the same time I disagree with the philosophical background involved in his argument.

    I'm much more sympathetic with Sean Carroll here, having moved long ago beyond the Popperian philosophy of Science, see What scientific idea is ready for retirement? (http://edge.org/response-detail/25322); falsifiability may not need to be retired but it is definitely just one of the methodologies used by science, being not the infallible criterion to demarcate science from non science thought by some Popperians.

    In short the Multiverse theory is a scientific research program (as is the string theory etc) but the level of justification for it at the moment (involving both theoretical and evidential aspects) is way too weak to talk even of provisional scientific knowledge (as a side note in my view all scientific knowledge, indeed knowledge in general, should be considered provisional and possibly corrigible in non trivial ways, even the best established knowledge should not be exempted from possibly being on the 'wrong branch' or a 'special case' in a deeper reality).

    Yet the future can be full of surprises, the case for the Multiverse can still become very well as compelling (via Rationality) for physicists as it is the inflationary scenario now, applying rigidly the criterion of falsifiability can only harm fully legitimate directions of research.
     
  18. Mar 8, 2015 #17
    This is sort of what I was trying to get at with my earlier post, although I'm not sure I agree that the criterion of falsifiability per se can only harm research. I still think falsifiability is what separates the scientific method from other modes of thinking, but, as you and I both suggested, just because a theory is not falsifiable right now does not mean we should summarily consign it to the dustbin along with aether, geocentrism and the like. A theory can still exist and have compelling mathematical arguments behind it, but testable predictions should still be what promote (or not, of course) a hypothesis to the realm of accepted scientific knowledge.
     
  19. Mar 8, 2015 #18
    Knowing absolutely nothing of physics, I depend on the intellect of others to row me across the lake; so to speak. When some hypotheticals such as strings theory or multiverses are hashed over, where does the theories come from? Is there ways of calculating their possibility, or physical proof that they can or do exist? I ask this only because, if they are just ideas, we all have a few to offer. Let me put one of Dr. Penrose's out there that hypothesizes a cyclic universe..

    I do like the theory but there is little I can offer other than ideas. But listening to the stutter steps he makes in explaining the theory baffles me. Very possibly there has been enough theory and calculus from Penrose and Hawking to go deeper into the possibility that such a universe may exist. With what is being found out about dark matter etc. and the increase in exansion velocity, many of the answers may be right in front of us. Can anyone help in looking into such a possibility further?
     
  20. Mar 8, 2015 #19

    Drakkith

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    Not necessarily. I've seen at least one multiverse theory that makes observable claims. I think it's important to make a distinction between what isn't observable in principle and what isn't observable because we just haven't seen it yet.
     
  21. Mar 8, 2015 #20

    Theories are 'free creations of the mind', to paraphrase Einstein, and it does not have any importance where they come from (dreams, sudden inspiration, religious beliefs, pondering on the consequences of accepted theories and so on are equally valid sources). What really count in science is the confirmation part, the theories should be testable, with some of the predictions separating them from the other existing hypotheses. If the theories (+ their auxiliary assumptions in reality) survive the test of reality and are (much) more confirmed than the alternatives then they usually become part of scientific knowledge, the 'normal paradigm' of the day.

    In the case of Penrose I suppose that his 'conversion' was triggered also by the existing proposals regarding the cyclical Universe (apart from the theoretical considerations he presented). Now in what regard the confirmation context I don't think we can advance any objective prior probability of such hypotheses being true and as far as I know no experiment indicates them as 'the winner' (they are falsifiable). Yet although at least some variants are still definitely viable (also in light of the fact that the results of BICEP 2 study was put in a different perspective by Planck observations) they are by no means the first choice program deserving to be pursued further at this time (not ultimately because they have lower coherence with the accepted body of scientific knowledge).

    To conclude anyone can propose hypotheses but only those which pass the experimental test can succeed to become science (although I really doubt that the scientific community will always pay attention to very good ideas coming from outsiders :) ).
     
    Last edited: Mar 8, 2015
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