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Re: Article: The Parallel Universes of David Deutsch

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  • Marchal
    ... You talk like if Nature necessarily exists in some primary sense, and that math are just tools for the mind. I am quite realist about numbers. Numbers
    Message 1 of 66 , Dec 31, 1969
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      Gordon wrote:

      >Even if your right Physics found that Comp and the Physical world where
      >related through the Philosophy of the Physical hence Objects.
      >I agree that our idea of Reality are hard to prove but that mite be just
      >down to or Language and nothing to do with the rest of Natures rules.
      >
      >Before most thought that at the Quantum level it wasn't real.At that
      >time Classical Physics had the Vector Potential which most took as not
      >real just a math Object in the mind however AB EFFECT should that not
      >only on the Quantum level it's real effect but it kicks back, now in our
      >words may make this non real again but Nature has a better Language than
      >us.Recently Physicist who thought that the Wave was just something of
      >Math in there head have said "I have to go pack it and think again about
      >how I see the world" this was after seeing the IBM stuff on
      >Scan-Tunneling Microscope Quantum corral.We are along way from the
      >finished Physical Program yet!


      You talk like if Nature necessarily exists in some primary sense, and
      that math are just tools for the mind.
      I am quite realist about numbers. Numbers kicks back in their own way.

      David Deutsch defends such type of number realism. Actually FOR
      endorses the three points which defined what I called comp.

      And I am just saying look, if comp is taken seriously enough we
      *have* to derive 'quantum computation' from what machines can possibly
      expect from their possible consistent computational histories.
      So I point on some work which *needs* to be done (and btw on some modest
      parts which has been done!).
      And, as gift, we get light on the mind body problem but also on the
      origin of physical laws.

      About the "finished Physical Program" I agree with you, both empirists
      and hard theoreticists are just nibbling the reality beast.
      I wouldn't be so astonished that comp makes possible to prove the
      impossibility of any unifying physical toes like if the set of
      elementary entities was not closed for diagonalisation: give me your
      particuls and I will show you a new one:) That is, although comp is
      ontologically "anti-empirical", it is almost quite sure that comp
      entails that some part of numberland can only be known by experimentation.
      (both from third and first person point of view).
      There will be forever machines saying as Rabi "who asks for that?"

      Would it be so astonishing for you that the fabric of reality relies
      eventually on cohering sheafs of deep and sharable "dreams" (i.e. some
      computations viewed from abstract (platonic) machines)?


      Bruno
    • Nick Kuneman
      just testing it sorry ... From: z_motyka Sent: Wednesday, March 06, 2002 1:12 PM To: Fabric-of-Reality@yahoogroups.com Subject: Re: Article: The Parallel
      Message 66 of 66 , Mar 6, 2002
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        just testing it sorry
        ----- Original Message -----
        From: z_motyka
        Sent: Wednesday, March 06, 2002 1:12 PM
        To: 'Fabric-of-Reality@yahoogroups.com'
        Subject: Re: Article: The Parallel Universes of David Deutsch

        In reply to brilliant post of Brian Scurfield [SMTP:brian.scurfield@...] of 2nd March, 2002
        Henry Sturman [henry@...] wrote (6th March):


        > It looks like you are mixing up two possible MWI's. <

        > MWI A would say that universes diverge according to the different paths they can take through slit 1 or 2. <

        > MWI B would say that universes diverge according to possible screen locations, whereby the number of universes (or the "thickness" of the universe) for each location is proportional to the wave amplitude squared at that location. <

        > MWI A does not seem to lead to an interference effect, since paths of photons going through a slit should be able to reach any point of the screen. <


        Not at all, especially when they starting from different slits in two different worlds have a chance to achieve the screen exactly at the same point in different worlds interfering into one common world. The universes diverged according to the different paths they can take through slit 1 or 2. Then those universes converged back into the one, where the photons occupy exactly the same position at the screen.


        > MWI B is possible and cannot be disproved. However, in MWI B there is no basis for making the claim that in each universe the photon goes either through slit 1 or slit 2, since a photon observed at the screen is an interference effect of a wave going though both slit 1 and slit 2 and the universes diverge only after that effect happens.<


        Why? The universes can not split as a result of interference*) (there is no differentiation in any defined point of the screen). They has only the one possibility (not two) (at least at the valleys and ridges of the interference pattern) for any defined point: They interfere constructively at the point belonging to ridge, and destructively at the point which belongs to the valley at the final screen.
        *) There should be some interference between splitting worlds, though, because the whole picture sould be pretty symmetric in time. (That what seems to us to be divergence may look like a convergence for any possible observator moving in some oposite direction of time through the multiverse :)

        >(...)
        > Perhaps you, or Deutsch, mean that a combination of MWI A and MWI B is taking place, let's call it MWI C, where universes first diverge according to photon path and then merge according to location. The "thickness" of the universe for each screen location is then proportional to the square of the combined wave amplitude of all photons arriving at that location. But this seems inconsistent. Such a thickness distribution does not conform to any sensible pre-interference distribution of universes based on different photon paths. Again, such a theory would need to be stated consistently before we can start talking about it. <


        There is no need in such a combination. MWI A and MWI B are the same MWI.
        Universes diverge according to possible screen locations, whereby the number of universes (or the "thickness" of the universe) for each location is proportional to the wave amplitude squared at that location (B). Universes diverge [still further] according to the different paths they can take through slit 1 or 2 (A).
        The final effect is that for some cases of possible two worlds (and actually much much more of them) they may interfere constructively at a defined point, because the paths of photons are equal (in length, so the photons are coherent in time) and photons achieve the same point at every shadow screen.

        In meantime worlds diverge further from point to point when photon is propagating by random, say with velocity c, through the empty space. In many points of the space between the screen and the two slits these worlds converge when the shadow photons meet their counterparts from other worlds and interfere constructively or destructively depending on the point of meeting and the degree of coherence (i.e., the chances of meeting possibly exactly at the same moment of time in both or more worlds, and this does depend on their previous paths). [By the way: Every time they interfere destructively their worlds ends dead from the point of view of cancellation hypothesis.]
        The slits are necessary only to filter out all possible paths but the two groups of them selecting only those, which are possibly to be in the same phase when going through both slits.

        Zbig






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