[extropy-chat] Is Many Worlds testable?
scerir at libero.it
Thu Jan 4 10:46:15 UTC 2007
>> it seems to me that MWI (not to mention Copenhagen!)
>> does not tell us what happens between times t1 and t2
> Please name the observation you have recorded during
> that interval that Copenhagen can explain but
> Many Worlds cannot.
Copenhagen used to explain it by means of an intelligent
act of non reversible observation. In "Physics and
Philosophy" (Harper and Row, 1958, New York) Heisenberg
writes "The observation itself changes the probability
function discontinuously; it selects of all possible
events the actual one that has taken place [...].
The discontinuous change in the probability function,
however, takes place with the act of registration,
because it is the discontinuous change of our knowledge
in the instant of registration that has its image in the
discontinuous change of the probability function."
So, in the example under discussion an observer may collapse
the superposition at time 2, observing and recording the
outcome. It seems to me that an observer may also collapse
the superposition at time t1, if, at that time. he becomes
aware of the fact that the alpha particle did not hit
the inner scintillating surface. Note that in the latter
case there is no real act of non reversible registration,
since there is no measurement at all, and there is just
a change in the knowledge of the observer (at time t1).
Note also that Born wrote: "how could we rely on probability
predictions if by this notion we do not refer to something
real and objective?". This is important since Copenhagen,
as we saw above, is inclined to mix the reduction of the
probability packet, the (subjective?) change of knowledge
(Heisenberg), the consciousness (von Neumann), and the
reduction of the probability packet.
The confusion becomes even greater when famous physicists
try to introduce subjective probabilities in the Copenhagen
As for the MWI I suspect there is also some huge confusion
(and not just in myself, but in general). Because the aim
of the MWI (as I understand it) is/was to explain physical
events at a quantum level. In other words its aim is/was
to avoid the 'black box' explanation given by Copenhagen,
that is to say an explanation (sort of) that is completely
_consistent_ at the classical level (observers, measurements,
non reversible recording), but which does not say what is
happening at the quantum level.
I'll try to re-think that infamous example (ie using the
probability calculus of the consistent histories, the Heisenberg
picture and not the Schroedinger picture, etc.) to see
if MWI is stronger and more consistent than Copenhagen.
But I do not have time at the moment.
>> Another problem I have is the one-slit diffraction
> (different from the two-slit interference)
> Things are indeed a bit more complex when dealing with diffraction rather
> that interference, and if Copenhagen can explain what is going on more
> clearly than Many Worlds then I have lost the argument.
Almost every one has lost his arguments: Einstein, Bohr, Schroedinger,
de Broglie, von Neumann, even John Bell. So, in that case,
you would be in a good company! (The MWI explanation of the one-slit
diffraction should to be a complex one, but I did not read anything
> Best regards. And I want you to know I'm really enjoying this debate;
> regardless if I end up winning or losing I want you to know I think you
> are a fine fellow.
I think all extropes are fine fellows.
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