John K Clark (johnkc@well.com)
Wed, 30 Jul 1997 22:53:47 -0700 (PDT)


On Thu, 31 Jul 1997 Damien Broderick <damien@ariel.ucs.unimelb.edu.au> Wrote:

>I have one reservation - I don't know that one can really combine
>decoherence and the Everett model, which seem to be alternative

As you know, you get an interference pattern when you fire a photon (or an
electron) at 2 slits even, even if you send them through one at a time.
It sure seems that something is going through both slits at the same time,
but what? Other interpretations say that it is an abstract pilot wave or
probability wave, Many Worlds is more concrete, it says it's just what it
seems to be, 2 photons interfering with each other, and this is true even if
you only send one photon. The other interpretations assume that there is only
one reality (or no reality at all), Many Worlds makes no such assumption.

Let's do the two-slit experiment, but instead of using film to stop the
photons after they pass the slit, let them head out into infinite space.
If Many Worlds is correct then the entire universe splits into 2 when the
photon hit's the 2 slits and never recombines. There is nothing special
about you the observer, you split just like everything else, you know that
the photon went through one and only one slit, but of course you have no way
of knowing which one.

Now let's do the more usual two-split experiment and put the film back in.
The universe splits just as it did before when it passed the two slits, but
when the photon hits the film and it no longer exists in either universe then
the 2 universes fuse back together again. Looking back we find evidence that
the photon (or electron) went through both slits and this causes an
interference pattern. Again there is nothing special about an observer in
this, the same thing would happen if nobody looked at the film, or even if
you used a brick wall instead of film, because the important thing is not
that the photon makes a record (whatever that is) but simply that it is
destroyed. Mind has nothing to do with any of this so I don't need to
explain it, or measurement, or representation, or categories, or

Does all this violate Ockham's Razor? I'm not sure. Invoking all those
universes is not exactly simple, but is it the simplest idea that explains
what's going on? The Many Worlds interpretation is cheap on assumptions but
expensive on universes.

>Hal will surely suggest some useful texts, but one that I found
>enjoyable (if somewhat difficult) is Murray Gell-Mann's own THE

That was very good, even better is "The Cosmic Code" by Heinz R Pagels,
"Quantum Reality" by Nick Herbert and "The Ghost in the Atom" edited by
P.C.W. Davies and J.R. Brown.

John K Clark johnkc@well.com

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