On 12/9/2013 5:31 PM, Jason Resch wrote:




On Mon, Dec 9, 2013 at 4:28 PM, meekerdb <meeke...@verizon.net <mailto:meeke...@verizon.net>> wrote:

    On 12/9/2013 12:06 PM, Jason Resch wrote:



    On Mon, Dec 9, 2013 at 12:57 PM, meekerdb <meeke...@verizon.net
    <mailto:meeke...@verizon.net>> wrote:

        On 12/9/2013 12:44 AM, LizR wrote:
        On 9 December 2013 20:56, meekerdb <meeke...@verizon.net
        <mailto:meeke...@verizon.net>> wrote:

            On 12/8/2013 4:36 PM, LizR wrote:
            On 9 December 2013 07:41, John Clark <johnkcl...@gmail.com
            <mailto:johnkcl...@gmail.com>> wrote:

                On Sun, Dec 8, 2013 at 11:48 AM, Jason Resch 
<jasonre...@gmail.com
                <mailto:jasonre...@gmail.com>> wrote:

                        >> Determinism is far from "well established".


                    > It's a basic assumption in almost every scientific theory.


                In the most important theory in physics, Quantum Mechanics, no 
such
                assumption is made, and despite a century of trying no 
experiment has
                ever been performed that even hinted such a deterministic 
assumption
                should be added in.


            I believe the two-slit experiment hints that QM is deterministic by
            implying the existence of a multiverse.
            Wasn't it you, Liz, that pointed out this was circular.  Everett 
assumes a
            multiverse in order to make QM determinsitic.

        I did say something like that, didn't I? [insert embarrassed emoticon 
here].

        I think I was saying that it was too strong to say that QM "follows the
        principle of determinism" (or something like that) because it appears 
to be
        indeterminate and only becomes deterministic thanks to Everett. 
However, the
        two-slit experiment does /suggest/ the multiverse as a valid 
explanation, in
        that any other explanation requires other principles to be violated
        (causality, locality...)

        I think I was attempting to position myself between John and Jason - to 
say
        that determinism is reasonably well established, but only as a result 
of a
        long and winding process of experiment, conjecture and so on.


        But it isn't.  As Roland Omnes says, quantum mechanics is a 
probabilistic
        theory so it predicts probabilities - what did you expect?  Among 
apostles of
        Everett there's a lot of trashing of Copenhagen.  But Bohr's idea was 
that the
        classical world, where things happened and results were recorded, was
        *logically* prior to the quantum mechanics.  QM was a way of making 
predictions
        about what could done and observed.  Today what might be termed 
neo-Copenhagen
        is advocated by Chris Fuchs and maybe Scott Aronson.  I highly recommend
        Scott's book "Quantum Computing Since Democritus".  It's kind of heavy 
going in
        the middle, but if you're just interested in the philosophical 
implications you
        can skip to the last chapters.  Violation of Bell's inequality can be 
used to
        guarantee the randomness of numbers, 
http://arxiv.org/pdf/0911.3427v3.pdf,
        assuming only locality.



    Bell's theorm proves that local hidden variables are impossible which 
leaves only
    two remaining explanations that explain the EPR paradox:

    1. Non-local, faster-than-light, relativity violating effects

    That's non-local hidden variable - which is exactly what a parallel 
universe is.


There is nothing non-local about Everett's theory. You start with the electron and positron left over from the decay of a pi meson. They are each in a superposition of having a negative spin in the y axis and a positive spin on the y axis, but they are correlated in the following way:

(e↑ × p↓) + (e↓ × p↑)

Then one electron is sent to Earth and the other to the closest star, Proxima Centauri, where they are measured at about exact same time. After the scientists on Earth measure the electron, the state is as follows:

(Earth↑ × e↑ × p↓) + (Earth↓ ×e↓ × p↑)

Where Earth↑ represents earth scientists who measured the electron to have an up spin and Earth↓ represents earth scientists who measured the down spin for their electron. So far so good, nothing non-local has happened, only people on Earth are affected by the measurement of the electron (they have become part of the superposition). A fraction of a second later, the scientists at Proxima Centauri (4 light years away) measure their position, and the resulting superposition becomes:

(Earth↑ × e↑ × p↓ × Proxima↓) + (Earth↓ ×e↓ × p↑ × Proxima↑)

So now the scientists at Proxima Centauri have become part of the superposition, having measured both possible values. There is no need to enforce at speeds faster than light, any kind of agreement with the measurement by the remote groups of scientists, since both scientists measure both outcomes.

Now when the scientists at Proxima Centauri measure their positron's spin, and send the result to Earth (to arrive 4 years later), the Earth scientists necessarily find that the radio signal indicates a result that corresponds to their own measurement. This is because the radio broadcast correlates with the measurement at Proxima Centauri, which is correlated with the positron, which is correlated with the electron, which is correlated with the measurement of the Earth scientists. Since they exist in distinct states of the superposition, it is impossible for the Earth↑ scientists to hear from or otherwise interact with the Proxima↑ scientists, the Earth↑ scientists can only hear the radio broadcast that comes from the Proxima↓ scientists.


Thus, the EPR paradox is solved without hidden variables (which were defined as extraneous properties not described by in quantum mechanical theory), and moreover, does so without violating special relativity. This solution comes directly from the literal reading of the Schrodinger equation. All the apparent paradoxes come from the assumption that collapse is fundamental.

If you want collapse to be taken seriously, you must show evidence for it commensurate with the evidence that exists for other concepts in physics, because if the Copenhagen interpretation is true, then special relativity is false, locality is false, time-reversibility is false, determinism is false, causality is false, quantum computers are impossible, and observers are magical. This is a lot to give up for an interpretation that is not well-defined (how and when observation triggers collapse and even observation itself are not even defined), inconsistent in its treatment of multiple observers, and shown by Everett to be entirely redundant given the Schrodinger equation.

Do you really think the Copenhagen interpretation is defensible given what we now know today?

Jason

You keep assuming that every criticism of MWI is a defense of real collapse - it isn't. I think a proper reading of Copenhagen is epistemic collapse; in any case that seems to be the viable alternative.

Brent

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