On 21 Jan 2014, at 09:43, Richard Ruquist wrote:
On Tue, Jan 21, 2014 at 1:30 AM, meekerdb <[email protected]>
wrote:
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).
And so when I am approaching a fork in the road while driving
and on one fork I will get into an an accident and on the other I
will not,
does that choice count as a superposition? Richard
If you choice is determined by a quantum event. But if your brain is
classical, then it will not.
But note that if you decide by throwing a coin, the heisenberg
uncertainty makes it that if you shake the coin enough, it will add
up, and become a quantum choice, and so, even if your brain is
classical, I can imagine processes leading to quantum superposition.
Bruno
Brent
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