On Tue, Dec 31, 2013 at 5:07 PM, Jason Resch <jasonre...@gmail.com> wrote:

> I would add a (*) on "observer role". In MWI the observer plays no
> special function in the evolution of the wave function. This is not the
> case for many interpretations where the observer plays some special
> privileged role, such as having the ability to collapse wave functions.

Yes, and that is why I believe the MWI is superior to other
interpretations, but that's only my opinion and the universe may have a
different one.

 > [your chart]  says for MWI the observer plays no part in many world but
>> it also says "no" to counterfactual definiteness meaning you can't speak
>> meaningfully of the definiteness of the results of measurements that have
>> not been observed.
> > That is true for MWI because measurements don't have (single) definite
> results.

Yes they do, the photon I just measured has a polarization of exactly
42.7%, true other John Clarks measured other photons and found other
values, but this john Clark got exactly 42.7% for this photon.

 >> Both those things can't be right.
> > Can you explain why not?

Not having counterfactual definiteness means something is NOT in a definite
state if you don't observe it, observer independent says they ARE in a
definite state even if you don't know what it is.

 >> And in many world there is no unique future but it says there is no
>> unique past, and that's not what the theory says.
> > There is no unique past as shown in the quantum erasure experiment.

OK you got me, I should have said with the MWI there is ALMOST a unique
past. According to Everett when 2 different things could happen then both
do, one happens in one universe and one happens in the other; for example a
photon goes through a half silvered mirror in one universe and is reflected
in the other. Usually after that the differences between the universes
increase and they remain separated for eternity, however if the initial
difference is very small and if you set up the experiment very very
carefully then the 2 universes might not further diverge but instead evolve
into identical states again. Because the 2 universes are identical again
they come back together and we in the single merged universe see evidence
that the photon was reflected off the half silvered mirror and equally
strong evidence that the photon went straight through the half silvered
mirror. The information to decide between these 2 possibilities no longer
exists in our universe because both past states could have evolved into the
present state.  But none of the possible alternate pasts we see from
looking back from our particular thread of the multiverse are very
different from each other, but our alternate futures can be radically

> The wave function says everything there is to be said about how something
> is right now.

The wave function says nothing about where the electron is right now, the
square of the wave function (I'm not being pedantic the distinction is
important) does tell you something but not enough, it can only give you
probable locations of the electron but it could be anywhere. You can find
out more and find out exactly where is is but to do that you're going to
need to get your hands dirty and perform a experiment, then the squared
wave function collapses from everywhere to one specific dot on a
photographic plate. This is the measurement problem and the problem that
the MWI elegantly solves that most other quantum interpretations do not;
it's the only reason I think MWI is better than the competition. But that
doesn't prove its correct of course, everybody could be wrong, maybe MWI is
just the best of a bad lot. The only thing I'm certain of is that whatever
turns out to be true will be crazy.

  John K Clark

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