[extropy-chat] Is Many Worlds testable?

Damien Broderick thespike at satx.rr.com
Sat Dec 30 17:53:26 UTC 2006

At 12:06 PM 12/30/2006 -0500, John K Clark wrote:

>"scerir" <scerir at libero.it>
>Whatever idea you were trying to convey in the above I have no doubt the
>English language is capable of expressing it in a much much clearer way, and
>by using only one third of the space too.

Given that Serafino is Italian, I think he might be excused.

>And ditch the diagrams, they don't
>work very well in ASCII.

Worked fine for me, helped get across his idea nicely.

>NO! The splitting or merging has nothing to do with measurements or
>observation or consciousness; the great advantage of MWI is it doesn't have
>to explain exactly what any of those things are.

Everett's paper is precisely about the measurement problem.

To quote von Neumann-Dirac theory to which was responding


"Dynamics: (a) If no measurement is made, then a system S evolves 
continuously according to the linear, deterministic dynamics, which 
depends only on the energy properties of the system. (b) If a 
measurement is made, then the system S instantaneously and randomly 
jumps to a state where it either determinately has or determinately 
does not have the property being measured. The probability of each 
possible post-measurement state is determined by the system's initial 
state. More specifically, the probability of ending up in a 
particular final state is equal to the norm squared of the projection 
of the initial state on the final state....

But what does it take for an interaction to count as a measurement? 
Unless we know this, the standard formulation of quantum mechanics is 
at best incomplete since we do not know when each dynamical law 
obtains. Moreover, and this is what worried Everett, if we suppose 
that observers and their measuring devices are constructed from 
simpler systems that each obey the deterministic dynamics, then the 
composite systems, the observers and their measuring devices, must 
evolve in a continuous deterministic way, and nothing like the 
random, discontinuous evolution described by Rule 4b can ever occur."

Damien Broderick 

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