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The Multiversians are at the gates!

  1. Sep 3, 2010 #1

    marcus

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    The Multiversans are at the gates!

    Remember the 2008 annual conference "Strings 2008" at Geneva, when the organizers excluded all "anthropic string landscape" and "multiverse" talks from being presented?

    And the November 2008 workshop at Princeton (Steinhardt, Arkani-Hamed, Banks...) that pretty much concluded the landscape fad (2003-2007?) was finished?
    http://www.math.columbia.edu/~woit/wordpress/?p=1285

    Try to stop Multiverse at a professional academic level and it just flows around you into the gullible public media--maybe it is just too tempting a way to sell books!

    Hawking's book "The Grand Design" is #1 seller today among all Amazon books. It goes on sale 7 September.
    https://www.amazon.com/Grand-Design-Stephen-Hawking/dp/0553805371

    Brian Greene's new title is scheduled to appear in January 2011 "The Hidden Reality--Parallel Universes and the Deep Laws of the Cosmos"
    https://www.amazon.com/Hidden-Reality-Parallel-Universes-Cosmos/dp/0307265633/

    So maybe we should talk about Multiverse thinking. What is it grounded in? Is there a basic scientific motivation for it?
     
    Last edited: Sep 3, 2010
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  3. Sep 3, 2010 #2

    marcus

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    Re: The Multiversans are at the gates!

    Here's what Hawking is quoted as saying as blurb for the new book:
     
    Last edited: Sep 3, 2010
  4. Sep 3, 2010 #3
    So Hawking believes in MWI (besides the Multiverse)
    Cool!
     
  5. Sep 3, 2010 #4

    atyy

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    Hmmm, the quote sounds more like he believes in the multiverse instead of MWI!

    Anyway, MWI is no longer MWI is it? It's just no collapse of the wave function, which is common to MWI and Bohmians, unified under decoherence, isn't it?
     
  6. Sep 3, 2010 #5

    marcus

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    Re: The Multiversans are at the gates!

    If an author is vague enough and talks about both MWI and bubble inflation multi in the same chapter, an average reader is probably not going to care about the difference.

    John Gribbin got in early on this. His book came out in September 2009 and is doing quite well, Amazon salesrank around 1100 when I looked today. The title of Gribbin's is:
    "In Search of the Multiverse: Parallel Worlds, Hidden Dimensions, and the Ultimate Quest for the Frontiers of Reality"
    For comparison here is Greene's title:
    "The Hidden Reality--Parallel Universes and the Deep Laws of the Cosmos"

    Greene's title recycles buzzers from Gribbin's title: "hidden", "parallel", "reality".
    Here's the page for Gribbin's
    https://www.amazon.com/Search-Multiverse-Parallel-Dimensions-Frontiers/dp/0470613521/
     
    Last edited: Sep 4, 2010
  7. Sep 3, 2010 #6

    marcus

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    Re: The Multiversans are at the gates!

    Here's my personal view of these developments. Maybe you'd like to disagree.
    What strikes me about most Multiverse stuff I hear is its uselessness as science.

    Maybe this is obvious and hardly needs to be said (if not please tell me):
    Science is about observing modeling predicting this universe.

    Indeed to get a good model in cosmology you DO make it extend beyond what we can hope to observe---in a 'more of the same' fashion. That is an OCCAM assumption because it is simpler than postulating some kind of boundary with different stuff out beyond.
    The portion of the universe that we do see behaves as if it were a part of a more or less uniform whole and it's simplest to understand and model that way.

    So science is about observing modeling predicting this universe (even though we maybe can't observe everthing or predict everything.)

    As Niels Bohr put it, the subject of [micro-scale] physics is not what nature IS, but what we can say SAY about it. Fundamental physics aims to understand at a microscopic level not what the world is made of, but how it responds to measurement.

    As Francis Bacon taught us in early 1600s, people shouldn't present us with theories that don't predict observable stuff. Theories should be empirical. That's the 400 year tradition of empirical science.

    It doesn't matter if the model is made of tinkertoy or erector-set or lego-blocks as long as it works. There can even be two equally good models. But they have to work, and tell us correct numbers---that fit what happens in this universe.

    Multiverse appears to be a fantasy---perhaps concocted to provide something for M-theory to rule over. Because M-theory (so far an unformulated, non-existent theory) has been unable to lock into this universe we live in but seems to lead to jillions of different versions of physics.

    Multiverse also appears to be a cop-out: getting off the hook of not providing an explanation for the big bang. Personally I expect that an explanation of what led up to bang will eventually be worked out and will make testable predictions that one can check against ancient light. But in the meantime some people prefer to give up on that and say the universe just happened because of "quantum uncertainty". This sterile idea leads to no predictions of observable phenomena. But it does lead to the imaginative vision of a vast array of bubble universes--because if one can spring into existence why not jillions?--and that splendid imagery can boost booksales and ratings.
     
    Last edited: Sep 4, 2010
  8. Sep 3, 2010 #7

    marcus

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    Re: The Multiversans are at the gates!

    Sean Carroll has posted a 3-minute talking head video of his own titled
    Stephen Hawking Settles the God Question Once and For All
    http://blogs.discovermagazine.com/c...ng-settles-the-god-question-once-and-for-all/

    Here's a quote from Nima Arkani-Hamed which I think is more sensible than any of this Multiverse buzz:

    ==quote==
    Finally, Arkani-Hamed ended with the statement that string theory is useful as a way to study questions about quantum gravity, but “unlikely to tell us anything about particle physics”.
    ==endquote==

    This was from Woit's report on the November 2008 symposium at Princeton on the string theory landscape. I gave the link in post #1 of this thread. If string, or M, is unlikely to tell us anything about particle physics this is presumably because it generates a vast landscape of possible versions of physics.
    In that case, one can start exploring other theories that will hopefully be more narrowly selective (Steven Weinberg, Alain Connes, Roberto Percacci, Hermann Nicolai have indicated at various times they have ideas.)
    Or does one cling to string and say that the world "really" consists of the huge landscape of versions that string predicts, rather than the one we know?

    And then, to make that idea more exciting, does one spice it up with the God/non-God issue? This seems like plain old hokum either on Hawking's part or on that of his interpreters. Why not forget about such big issues and just get to work on better/more selective explanations of the world we observe?

    Here's a 3 minute BBC news clip on Youtube with Hawking reading a short passage from his book, and some commentary

    Here is a 10 minute BBC Youtube with more commentary, a bit bland and long.
    Stephen Hawking: Physics leaves no room for God
     
    Last edited by a moderator: Sep 25, 2014
  9. Sep 4, 2010 #8
    MultiVerse Theory makes String Theory look like Real Science.

    From what I can tell new universe is created for every possible outcome. Lets take one gram molecular Weight of Uranium for instance. At any instant any of those 6.02 e 23 atoms could decay. So we would need 6.02 e 23 univeses EACH INSTANT to account for each of these outcomes. And each one of those univeses would need 6.02 e 23 universes each instant to account for the uranium in each of those universes. Of course any atom in the univese could suffer neutron decay at any instant, so we now need a new universe every instant for every atom in the universe. All of this created from nothing.

    Or maybe its just things that are measured. So we take the same lump of uranium and as soon as we hold a geiger counter near it it starts creating universes from nothing.

    Need I say that this is silly.

    Personally, I would propose that if we don't need a creator for the universe, maybe we need an observer to collapse the wave forms, so that Sroendingers cat is really is alive or dead, becasue the unniversal observer can see it even if we can't.
     
  10. Sep 4, 2010 #9
    Your argument derives from philosophy not science and String Theory in itself is greatly incomplete and only brushes what is science in the context of Multiverse.
     
    Last edited: Sep 4, 2010
  11. Sep 4, 2010 #10
    Re: The Multiversans are at the gates!

    I agree with pretty much all you say here, Marcus. And it does need saying. When multiversian guff starts being promoted as science, and a search for M-Theory occupies shoals of very intelligent physicists for long years, fashions they are a-changing. The last and most important member of your trinity of physics virtues; "observing modeling predicting" may be in the process of being discarded.

    On today's physics frontiers (strings, different flavours of quantum gravity, entropic gravity, entropic everything) it is often impossible or impractical to predict (rather than just explain what has been observed or measured). Instead, faut de mieux, it is becoming fashionable to place faith in plausible logical argument and mathematical ratiocination, i.e. in modelling to fit known observation.

    Maybe this signals the transformation of physics into an art form, rather than a science?
     
  12. Sep 4, 2010 #11

    tom.stoer

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    My problem with all this multiverse stuff is simply that it is claimed to be derived from theories that are incomplete and partially purely understood. Why should I believe in metaphysical concepts X, Y,... derived from an incomplete theory which is not able to explain physical entities a,b,c,...? Why should I do metaphysics instead of physics?

    Introducing unobservable concepts is not forbiden in physics, but there should be the payoff of increased predictability.
     
  13. Sep 4, 2010 #12

    MTd2

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    Multiverse is not even science at any level whatsoever. String Theory cold be at least tested, in principle, with a really huge and powerful particle accelerator and a very sensitive detector. Multiverse is just a fluke.
     
  14. Sep 4, 2010 #13
    The multiverse is a paradigm and while currently it leads to no predictions this does not mean that one day it will. Think of the paradigm of the atom which goes back to the ancient greeks. It was only thousands of years later that the atom was used to understand physics and predict new physics. The point is that a new paradigm allows one to formulate new models of the universe which could not exist within the old paradigm. The multiverse therefore offers a frame work in which to build new models of cosmology. These models can then offer predictions which can be tested.


    I think many posts on here seem to offer a somewhat narrow view of what science is.
     
  15. Sep 4, 2010 #14

    MTd2

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    Multiverse does not any new framework. It just shows that universes that we cannot observe exist. This is not like the many worlds interpretation of quantum mechanics in which every world has an interference on others.
     
  16. Sep 4, 2010 #15

    tom.stoer

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    If one new testable prediction arises from the multiverse hypotheses I am willing to accept it a physical concept. Otherwise it's metaphysical speculation. Don't get me wrong - metaphysics is not irrelevant, uninteresting, ridiculous or something like that. But it is not physics.
     
  17. Sep 4, 2010 #16

    marcus

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    There are several pictures that one can call Multiverse. As most of us probably realize, Smolin has proposed a picture which he claims makes a testable prediction---because it includes an observable reproductive mechanism (collapse to astrophysical black hole) accompanied by gradual mutation of parameters. If the cosmos actually did proliferate by such a mechanism one would predict that the parameters of physics would typically be such as to favor the reproductive mechanism---and not be improvable by any small change.

    So far, says Smolin, no one has discovered any small change in the standard models of particle physics and cosmology that would have caused formation of more astrophysical black holes.

    I don't want to promote that particular multiverse story here, and I don't think it is what today's popular Multiverse books are presenting. I just want to acknowledge that in very special cases some kind of testable prediction is possible.
     
  18. Sep 4, 2010 #17

    marcus

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    Re: The Multiversans are at the gates!

    Actually what concerns me about today's Multiversans is what I take to be a careless disregard for testability.

    By itself multiversery is simply the notion that the cosmos might have different regions with different physical parameters. We have no reason to object, as long as they can point to a testable prediction from such a model.
    Too often it seems as if a multiverse message is being used as a cover or excuse for theories not making any predictions at all.
     
    Last edited: Sep 4, 2010
  19. Sep 4, 2010 #18

    Fra

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    Re: The Multiversans are at the gates!

    I share alot of the objections to multiverse thinking that has already been mentioned but to just add my additional opinons...

    I can see two ways to arrive at "multiverse" reasoning.

    1) By means of considering "mathematical possibilities" of structure of reality, and try to interpret them as different universes, but where only one of them seem to corresponds to the world we live in.

    My opinion there is that misguided confidence in the "reality" of these mathematical possibilities then imply the confidence in these multiverses.

    But it's utility or point is still UNclear. The attempts i'm aware of such as anthropic arguments as to why only some support life seems like irrational desperate arguements to seek a way out of the trap created by the misguided confidence in "mathematical possibilities" with no lack of physical evidence.

    2) By confusing "many observers" with "many worlds". IMO, structural realism as a rejection of too much subjectivity risk leading to multiverse conclusions. If several possible conclusions seems possible and you fail to recover the consistency by simple observer-observer transformations like we are used to, then it seems like a short step to assume that these represent different universes and that these observers live in different universes and thus will never interact = problem solved.

    But this is IMHO, cause also by insisting on structural realism in certain forms. I'm not saying that structural realism must lead to multiverses, but I personally see a relationship.

    /Fredrik
     
    Last edited: Sep 4, 2010
  20. Sep 5, 2010 #19
    Re: The Multiversans are at the gates!

    testability? falsiability?
    who is talking about that stuff now? :)
    seriously, what is a difference between talking about infinite Universe (hence making unfalsifiable claims about something beyond our hubble volume and even beyond the cosmological horizon) and talking about multiverse in MWI sense or superstring/bulk sense?
    The first type of multiverses is called type I by Max Tegmark, others are called type II and III. But they are all unfalsifiable.
     
    Last edited: Sep 5, 2010
  21. Sep 5, 2010 #20

    marcus

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    I recall Tegmark's colorful SciAm article of some years back. As I recall there were 4 types of Multiverse, but maybe you are right and there were just 3 types. Intriguing exercises of imagination, for those who like such things.

    I don't want to argue with you about Einstein's "cosmological principle". Basically it is an Occam simplicity and burden-of-proof issue.
    As long as we see no phenomena indicating NON-uniformity, the default assumption is simply a bland boring "more of same".

    And no elaboration needed as to what "more of same" means. It is simply same enough to have no effect on us. We don't need to make up fantasy details, like different laws of physics or two-headed people.

    If you like to do that, you CAN make up fantasy details and you can calculate the probability that within a certain number of lightyears there would exists a planet just like Earth except the Confederacy won the Civil War. My feeling is that it is literature and that we don't need to do that from a science standpoint, but anyone who wants can do it for entertainment. Sort of recreational mathematics, or recreational cosmology.

    Max Tegmark's illustrated Multiverse article in the SciAm had quite a bit of that, as I recall.
     
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