R: Possible Worlds, Logic, and MWI

From: scerir <scerir.domain.name.hidden>
Date: Sat, 11 Jan 2003 23:58:31 +0100

Tim May:
> (Again, I currently have no pet theory of what Reality is. But I'm
> happy to be building a base of tools to be able to more intelligently
> comment later. Having a pet theory is not so important.)

The best definition, imo, is:
"Reality is that which,
when you stop believing in it,
does not go away."
- Phillip K Dick, in an essay (1978) titled "How to Build a Universe
that Doesn't Fall Apart Two Days Later." A Canadian coed asked him
(1972) to define reality for a philosophy class she was taking.

Leibniz also wrote: "although the whole of this life were said to be
nothing but a dream and the physical world nothing but a phantasm,
I should call this dream or phantasm real enough if, using reason
well, we were never deceived by it."

> * Borges. I mentioned him because of his seminal "Garden of Forking
> Paths" story. He was not the first to write about alternate
> histories...I'm not sure who wrote the first recognizable story in this
> genre. Probably as old a concept as any.

Somebody thinks that J.L. Borges was an Everettista :-)

The Aquinas and Wyclif (and also Ockam!) wrote about
the possibility of many universes, created by God.

Sometimes I feel there is something good with MWI and
there is something wrong with orthodox QM ....
Consider a diaphragm, with two slits, slit 1 and
slit 2. Each of these slits can be opened, or closed,
by a shutter connected with a separate counter.
A weak alpha-particle emitter is placed between
the two counters. Imagine that, in the beginning
of the gedanken experiment, both slits are closed.
If an alpha-particle strikes one of the counters,
the slit connected with this counter is opened,
and the counters cease to operate, and a light-source
is turned on, in front of the diaphragm, and this
light-source illuminate a photographic plate placed
behind the diaphragm. Following qm rules, we can write
        psi = 1/sqrt2 (psi_1 + psi_2)
where psi_1 is the wavefunction describing the system
when the slit 1 is open (psi_2 when the slit 2 is open).
Thus, from the theory, we'll get the usual interference
pattern, on the photographic plate behind the diaphragm.
But if we keep our eyes opened, and we observe which slit
is open (slit 1, or slit 2) then, in accordance with the
complementarity principle and the projection postulate,
a reduction takes place, and no interference pattern *should*
appear on the plate.
[L. Janossy, K. Nagy, Annalen der Physik, 17, 115-121, (1956)]
- Gottfried Wilhelm Leibniz [The Monadology, 64-66]
<But the machines of nature, namely, living bodies, are still machines
in their smallest parts ad infinitum. It is this that constitutes the
difference between nature and art, that is to say, between the divine
art and ours. And the Author of nature has been able to employ this divine
and infinitely wonderful power of art, because each portion of matter is not
only infinitely divisible, as the ancients observed, but is also actually
subdivided without end, each part into further parts, of which each has
some motion of its own; otherwise it would be impossible for each portion
of matter to express the whole universe. Whence it appears that in the
smallest particle of matter there is a world of creatures, living beings,
animals, entelechies, souls. Each portion of matter may be conceived as
like a garden full of plants and like a pond full of fishes. But each
branch of every plant, each member of every animal, each drop of its
liquid parts is also some such garden or pond. And though the earth and
the air which are between the plants of the garden, or the water which
is between the fish of the pond, be neither plant nor fish; yet they also
contain plants and fishes, but mostly so minute as to be imperceptible to
Received on Sat Jan 11 2003 - 18:01:25 PST

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