On 1/20/2014 5:56 PM, Pierz wrote:
A second question/thought on MWI. MWI proposes that the entire universe splits at the
point of wave collapse, or rather that it is continually and infinitely splitting with
every possible quantum state. This has been understandably criticised as a vastly
extravagant explanation. A whole universe, or even infinity of universes, for every
quantum interaction seems a high price to play to eliminate the weirdness of wave
collapse. Yet it seems to me that we can still get the explanatory benefits of MWI
without this extravagance by seeing the situation slightly differently.
I'll explain by analogy. I'm a coder. In the old days I used to back up my work by
making a complete copy of it and putting it in an archive folder. Nowadays I use git, a
source control system that keeps track of the history of my code and allows me to revert
back changes to an earlier point in time. Depending on how often I "commit" my work, I
can have an arbitrarily fine level of versioning. If git was stupid, it would copy my
whole code repository every time I committed a change, and my disk would rapidly fill
up. It would also be impossible to merge the work of another programmer working on the
same code base because the system would only have complete individual snapshots. It
would have no information about *what* changed between snapshots. But git is smarter
than that. It records only what I changed in each commit. Thus I don't have to worry
about my disk filling up, and I can happily merge someone else's changes - just so long
as we don't both try to change the same line of code.
To think that in MWI, a *whole other universe* is created when a binary quantum event
occurs is like imagining the multiverse works like my old backup system. One thing
changed, so if I want to keep a record of the earlier state, I have to copy
*everything*. This is the way that Deutsch seems to talk about the situation. But it
makes more sense to me to think of it as like git. If the universes diverged by only bit
of information, that one bit is the only thing that is "recorded" so to speak. When the
spin of a particle is measured here on earth, causing the universe to split, there is no
need at this point to think that there are suddenly two Plutos, one for each spin state.
What does Pluto know about the change? Later, this one bit change will ramify out,
causing divergent information flows in the two "universes" which will eventually lead
(possibly? necessarily?) to two completely different universes. But to the extent that
any region of one universe is identical to a region of another universe in the
multiverse, shouldn't we regard those regions as belonging to one and the same universe,
merely with the potential to differentiate from one another?
In other words, we're better off thinking about locally branching information flows than
an infinite filo-pastry of universes. We can still answer the question of where the
computations of a quantum computer take place - they occur in a multi-dimensional local
information space. Each calculation line that contributes to the final result occurs on
its own information thread as it were, but it does not require a whole universe to occur
in.
Maybe this economical view is the way MWI theorists actually do see the situation? If
so, I wish they'd talk that way. It makes the theory a lot easier to swallow in my view.
I agree that the "multiple worlds" generally differ only microscopically and so the count
as the same world so far as we're concerned. But the changes/divergences are not
discrete. A radioactive atom is in a superposition of decayed and not-decayed and on the
decayed side there is change of the wave-function propagating at c or less that is
gradually differentiating one world from the other at a microscopic level UNTIL in some
world the decay is detected and amplified (say by a geiger counter).
Brent
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