Re: MWI

On 30/05/2013, at 6:56, "hibbsa" <hibbsa-/[email protected]> wrote:

> 
> 
> --- In [email protected], Bruno Marchal <marchal@...> wrote:
> >
> > On 27 May 2013, at 16:33, hibbsa wrote:
> > 
> > >
> > >
> > > --- In [email protected], Bruno Marchal
> > > <marchal@> wrote:
> > > >
> > > >
> > > > On 27 May 2013, at 14:32, hibbsa wrote:
> > > >
> > > > > Does this question an answer?
> > > > >
> > > > > Is it logically possible for the multiverse to produce macroscopic
> > > > > universes exhibiting any statistically significant differences than
> > > > > our own universe?
> > > > >
> > > > > I mean "statistically significant" in the most rounded possible sense.
> > > > >
> > > > > - Any difference that our universe couldn't have gone the way of,
> > > > > consistent with its initial conditions all laws of physics assumed
> > > > > constant
> > > > >
> > > > > - Any difference in terms of any phenomena existing at any level of
> > > > > abstraction in greater or lesser or with any difference in any
> > > > > attribute including (a) abundance (b) probability of occurrence (c)
> > > > > relation with other phenomena (d) internal constituents.
> > > > >
> > > > > - Any difference on any level at all where to be different at the
> > > > > bottom level requires contradicting the probabilistic rules of QM
> > > > > and/or causing unique consequences of those rules as a result of
> > > > > interaction with macroscopic phenomena and at the top level requires
> > > > > any significant difference in the timing, macroscopic and
> > > > > microscopic structure, and ultimate fate of the universe.
> > > > >
> > > > > The reason I think this question deserves a proper full answer. And
> > > > > by that I mean...not just a criticism of the way the question is
> > > > > formed is because there could be important consequences...which may
> > > > > not be worked through. And the philosophy is all about intrepidly
> > > > > working through the consequences?
> > > > >
> > > > > I've got some consequences waiting for your criticism. But I think
> > > > > it's important to establish your criticism or acceptance of the
> > > > > above first.
> > > > >
> > > >
> > > > What do you mean by "exhibiting any statistically significant
> > > > differences than our own universe? "
> > > >
> > > > If you prepare an electron in the up + down state, and if you measure
> > > > its up/down state, QM predicts that you will end up yourself in the
> > > > "seeing-up + seeing-down" state. If you had decided to go in the North
> > > > or in the south, according to the result of that measurement, you end
> > > > up in the visiting-North + visiting-South. from your points of view
> > > > that is statistically different, imo. You get two macroscopically
> > > > quite different lives. This with a probability 1/2, when evaluated
> > > > before the measurement, about your future first person points of view.
> > > >
> > > > Now if your question is just "is there a macroscopic world in which
> > > > elephant can fly?", the answer is also "yes", but the probability,
> > > > here-and-now, that you will see such an elephant is equivalent to
> > > > winning the big lottery every second for a time much bigger than the
> > > > age of the universe, so don't count on it. Near death, that question
> > > > is just much more complex to get an answer today.
> > > >
> > > > The MWI is just the statement that the SWE applies to everything,
> > > > macrosocopic, mesoscopic, microscopic, etc.
> > > >
> > > > OK?
> > > >
> > > > Bruno
> > > >
> > >
> > > Hi Bruno - no not OK but my fault. I meant statistically different
> > > macroscopic universes. So you need to name your macroscopic
> > > object...preferably with clear, known emergent properties. And show
> > > how those emergent properties are altered in any of its associated
> > > quantum histories, from say,....the differences that would be
> > > exhibited by enough copies of the object in this universe to
> > > represent all the possible quantum histories.
> > >
> > > And if there aren't any differences...and if our macroscopic world
> > > is emergent phenomena from the quantum state, then it's hard to see
> > > how the multiverse can exhibit statistically significant differences
> > > between its macroscopic universes.
> > >
> > I am still not sure I really grasp your question. Planck constant is
> > very little. So if you decide to boil some water, QM predicts that it
> > will boil normally in most of the branches you can access in the
> > multiverse, with some non negligible probability. Then you will have
> > the many universes fluctuating from that behavior, but,
> > proportionally, they will be rarer. At the extremal point of the
> > spectrum of the possibilities, you will have the "Harry Potter"
> > universe, but those are quasi-impossible to access (a good thing),
> > except perhaps near death, as the probabilities on the first person
> > expectancies get harder to compute.
> > 
> > Our macroscopic world is not emergent from the multiverse, except for
> > most quantum properties, so our universe is quantum normal, with
> > solid, liquid and gaz well described by the quantum statistics. but
> > each branches differ on orthogonal or quasi orthogonal state, and so
> > can differ in macroscopic properties (like if earth was not hit by an
> > asteroid a long time ago), but such branches will still obeys the same
> > macroscopic laws, like classical mechanics, for example.
> > 
> > Our local realities are Gaussian, and that's why we can discern all
> > sort of laws. In fact that appears with just computationalism too.
> > Below our level of substitution, we emerge from infinities of
> > computations, which interfere statiostically, but above that level, we
> > have much simpler classical laws. In QM this is explained by MWI +
> > decoherence. With digital mechanism it is far more complex, but then
> > we can explain where the quantum comes from.
> > 
> > I hope this help, feel free to make your question more precise, if I
> > miss your point,
> > 
> > Bruno
> > 
> 
> Sorry for the delay...I just wanted to think about your response for a couple of days. 
> 
> One of the issues is that what I'm saying here about emergence and emergent properties is very much based on David Deutsch's BoI book and also his version of MWI. 
> 
> I'm not saying your points aren't valid or important....but would it be possible for you to reference his Reality of Abstractions chapter and then answer the question ,more generally in terms of emergent properties as he defines them? 
> 

He states, on page one of that chapter, that emergent phenomena are a "tiny minority" of phenomena. He also talks on page 5 of my kindle edition, about the arrow of time and the second law of thermodynamics. Disorder tends to increase. Energy is reduced in "quality" as time goes on. So although it is possible for water placed in a kettle to freeze...this is crazy unlikely. David explains on that page that it is unknown if the second law can be derived from lower level physics. The second law seems fundamental though. 

Will there be universes where the second law *does not hold*? No.

There will be universes where it might seem not to hold...but they are Harry Potter universes again.

A universe where the second law did not hold would not be very interesting for long. What would happen would be that time would *appear* to go backwards. But that would just be appearances. It would just be that things would get more ordered as time went on. So stars and galaxies would become warm nebulae which would then collect together and, I guess either form some great solid mass or just spread out uniformly throughout space in some huge crystalline structure. It would be a boring universe. And at any instant, this order would be shattered, in complete accord with the laws.
> 
> The basic argument from me is that, since macroscopic reality is in terms of emergence, for the multiverse to produce a significantly different macroscopic world, it would have to change the emergent properties. 
> 
Yes, if what *you* mean by "properties" means "physical objects". If you mean "emergent laws" then no, even these would be the same. Consider that if there was a universe where the internal combustion engine did not exist, the laws governing that engine still would. Likewise, a universe with no life would still have laws governing predator-prey relationships...they just would never be "instantiated" (so to speak).
> 
> I appreciate you've pointed to a Harry Potter world...but surely...that world can also be understood in terms of something that * might*, or *might have* happened in this world? 
> 
Yes. That's exactly how we do understand such universes...as places where it is highly unlikely anything like that might (or might have) ever happened.

Brett


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