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The anthropic principle(s) and the landscape

  1. Jun 17, 2006 #1
    In the thread on Peter Woit's new book, the conversation turned to the landscape currently predicted by string theory. This in turn led to me asking a question about Leonard Susskind, and his use of one form of the anthropic principle.


    Danger, Will Robinson! :surprised There are many versions of the anthropic principle, and as I understand it, Leonard Susskind only uses the least controversial one.

    There are many interpretations of the anthropic principle:

    (1) Weak anthropic principle (WAP): It can be defined as saying that the observed values of physical and cosmological quantities are not equally probable, but - at least in our universe - have obviously the values restricted by the requirement that there exist sites where carbon-based life can evolve. Further, at this time, the Universe must be old enough for life to have already arisen.

    This weak version, as I understand it, is the only one accepted by Susskind. The question, however, is whether or not one can use this to make testable predictions. (Maybe not, but can we be certain?)

    Note that the weak version appears in several forms.

    (2) Strong anthropic principle (SAP): "The Universe must have those properties which allow life to develop within it at some stage in its history."

    However, another version of SAP is much more bold:

    "The strong anthropic principle is simply the classic design argument dressed in the modern garp of cosmology. It implies that the production of life is part of the intent of the universe, with the laws of nature and their fundamental constants set to ensure the development of life as we know it."

    I reject this argument as mystical nonsense.

    ("The Rejection of Pascal's Wager")
    http://www.geocities.com/paulntobin/finetuned.html


    (3) The participatory anthropic principle (PAP) utilises a well known phenomena in quantum mechanics called the collapse of the wave function. In a nutshell this notion involves the peculiar property of the quantum world (such as the behaviour of an electron in double slit experiments) which seems to imply that something does not become "definite" until it is actually measured. Thus ostensibly implying that it takes an act of observation by a conscious observer to make it "real". PAP, first introduced by John Wheeler in the book Quantum Theory and Measurement co-authored with W.H. Zurek, suggests that observers must exist to bring the universe into being.
    (Quoted from "The Rejection of Pascal's Wager")

    Again, I reject this as mystical nonsense.


    (4) Final anthropic principle (FAP): "Intelligent information-processing must come into existence in the Universe, and, once it comes into existence, it will never die out." (This too exists in several forms.)

    I reject this as obviously wishful nonsense.


    I ask readers to consider: Are we rejecting every single interpretation of the anthropic principle, or just some interpretations? And if you accept that some form of the weak anthropic principle is true, then might we not make some testable prediction based on it? If not, how can we be so sure that no possible prediction can be made?

    Adherents of some forms of the anthropic principle are often accused of argument by lack of imagination. But I am wondering if that may be true of those who reject any possible predictions being made at all? (I don't know, I am just wondering.)

    http://en.wikipedia.org/wiki/Argument_by_lack_of_imagination

    Perhaps we need a guideline for discussing this topic: When agreeing or disagreeing with an interpretation of a theory, let's clearly state which interpretation we are talking about. Unconsciously everyone assumes this with QM, but I'm not sure that we always do this with the anthropic principle.


    By the way, some people think that the landscape currently predicted by string theory is far too small. :eek: Have you read the following paper by Max Tegmark? He has multiverses on top of multiverses on top of multiverses! (A shorter version of this recently appeared in Scientific American.)
    http://arxiv.org/abs/astro-ph/0302131

    Tegmark writes:

    I survey physics theories involving parallel universes, which form a natural four-level hierarchy of multiverses allowing progressively greater diversity.

    Level I: A generic prediction of inflation is an infinite ergodic universe, which contains Hubble volumes realizing all initial conditions - including an identical copy of you about 10^{10^29} meters away.

    Level II: In chaotic inflation, other thermalized regions may have different effective physical constants, dimensionality and particle content.

    Level III: In unitary quantum mechanics, other branches of the wavefunction add nothing qualitatively new, which is ironic given that this level has historically been the most controversial.

    Level IV: Other mathematical structures give different fundamental equations of physics. The key question is not whether parallel universes exist (Level I is the uncontroversial cosmological concordance model), but how many levels there are. I discuss how multiverse models can be falsified and argue that there is a severe "measure problem" that must be solved to make testable predictions at levels II-IV.


    Tegmark sounds quite mad. I'd rather enjoy meeting him. :smile:

    Happy reading!

    Robert
     
  2. jcsd
  3. Dec 22, 2010 #2
    Your understanding of the strong anthropic principle is wrong because it is stereotypically incomplete, since the choices are not simply chance or design, as there may very well be a simple physical *need* for carbon based life as a necessary function of the thermodynamic process, (for one example only), which makes your rejection of it a matter of educated opinion that puts you in direct opposition with Lenny whom you wrongly interpreted as follows:

    Leonard Susskind only uses the least controversial one.

    This is only conditionally true because Lenny applies the **observation** to the multiverse, but it is false without a complete theory of quantum gravity to justify it, because it is based on Lenny's observation that... "we will be hardpressed to answer the IDists if the landscape fails"... since... "the appearance of design is undeniable"... so, contrary to what any of these ideologically predisposed scientists would really like to admit... the direct observation is very STRONG.

    http://knol.google.com/k/the-anthropic-principle#

    Unless you're Vic Stenger, then you find rationale to say that the appearance is deniable... and then the best that you can possibly hope for is a difference of opinion among authoritative sources as to whether or not the observation is strong or non-existent, and one would think that any and all physicists would embrace and further investigate any plausible solution to the many decades-long-standing-problem of the flat, yet barely expanding universe from first physics principles before they would ever resort to cop-outs on science, like... the multiverse.

    But they don't, because Brandon Carter was right about the dogma that scientists harbor in spite of the evidence, and that's why you didn't even realize all this stuff until I pointed it out ... and that is because scientists, like Peter Woit, are Copernicanism practicing religious fanatics who, like Vic Stenger, are willfully ignorant of the MOST APPARENT strong implication that is inherent to the OBSERVATION within the "appearance of design" that is "undeniable" to Lenny and a FEW other reputable physicists who are willing to at least **conditionally*** acknowledge the implication of the observation like Lenny does.

    And just an FYI, but the "Goldilocks Enigma" as Paul Davies refers to it, makes numerous falsifiable predictions about exactly where life will and will not be found in the observable universe, and I think, with some HONEST investigation from this perspective you would find that appearance is telling scientists that the universe is NOT infinite, and there is not more than one universe... for starters.

    Design, chance... and NECESSITY... the latter being the elephant in the room or the huge sore thumb that dogmatically distorted left winged activist physicists refuse to recognize because hard left leaning liberal scientists can find god in the observation even faster than a freaking creationist can!

    And now you have the whole story from the only truly unbiased source that you'll ever get it from... and, for all the good it'll do... you're welcome.

    Let the denial begin...
     
    Last edited: Dec 22, 2010
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