# Re: How does this probability thing work in MWI?

From: Russell Standish <R.Standish.domain.name.hidden>
Date: Wed, 24 Nov 1999 15:49:45 +1100 (EST)

>
>
>
>
> >From: hal.domain.name.hidden
> >To: everything-list.domain.name.hidden, fritzgriffith.domain.name.hidden.com
> >Subject: Re: How does this probability thing work in MWI?
> >Date: Mon, 22 Nov 1999 17:24:34 -0800
> >
> >Fritz Griffith, <fritzgriffith.domain.name.hidden>, writes:
> > >
> > > ok, I understand that QM defines the probability of which universe we
> >will
> > > end up in.
> >
> > > [...]
> >
> > > Unfortunately, for
> > > every world that was expected to happen, there will be AT LEAST AS MANY
> > > WORLDS THAT WERE UNEXPECTED BUT DID HAPPEN, observed as a whole by the
> >SAS's
> > > of all universes. So, no matter what kind of reasoning you apply to QM
> > > probabilities, the unexpected will happen to all but a very small
> >minority
> > > of SAS's. How can we be so lucky as to be among that small minority?
> >
> >This is only a puzzle if you think that we need to be lucky to be among
> >a small minority. But the only way that we'd have to be lucky to be
> >among that minority would be if it were improbable.
> >
> >However earlier you wrote that you understood that QM defined
> >probabilities about which universe we would end up in. And these are
> >not equal probabilities. We are much more likely to find ourselves as
> >certain SAS's than as others.
> >
> >Therefore we don't have to be "lucky" to find ourselves among a certain
> >small minority of SAS's. In fact this is by far the most likely outcome.
> >
> >Hal
>
>
> All worlds are real, whether or not they will be ours. Therefore, you
> cannot assign probabilities to how likely it is a world will exist; every
> world has a 100% probability. You can say the same for anything within any
> number of worlds. There is no maybe, it WILL exist. SAS's are simply
> objects within worlds. You can say that all of them are real. When we
> define probabilities for worlds, we are simply saying which SAS's we are
> most likely to end up as. So you can imagine a split, which creates world A
> and world B. World A is the expected world, where we observe the universe
> to act as it should. World B is the unexpected world, where we observe the
> universe to act strangely. Both worlds are real, both exist. So whenever
> our world splits into a world we expect, there is another world, just as
> real, which for all of time acted as expected, for which we had no reason to
> expect anything different from. But all of a sudden, that world went
> haywire, leaving us baffled.
>
> The three important things to remember here are:
> 1. Both worlds are real.
> 2. The SAS's within each world are real.
> 3. Both worlds acted exactly the same for all of time until that one
> moment. Therefore, the SAS's within the unexpected world had observed the
> same physical laws, with the same degree of stability, as the expected
> world, right up until that moment. They too expected to be in the likely
> world; they had no reason to expect anything different. But, to their
> incredible surprise, they didn't end up in that world.
>
> Given these three conditions, I see no reason why our world is any more
> likely to be one than the other.
>
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>

Unless I'm much mistaken, this is simply a restatement of the White
there are some differing opionions on how to resolve the issue, but I
suggest you follow up references to this issue in the everything list
archive on http://www.escribe.com/science/theory/ to prevent endless
repetitions of what has been discussed already.

----------------------------------------------------------------------------
Dr. Russell Standish Director
High Performance Computing Support Unit,
University of NSW Phone 9385 6967
Sydney 2052 Fax 9385 6965
Australia R.Standish.domain.name.hidden
Room 2075, Red Centre http://parallel.hpc.unsw.edu.au/rks
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Received on Tue Nov 23 1999 - 20:48:41 PST

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