From: Amara Graps (amara@amara.com)
Date: Sun Jan 20 2002 - 03:53:57 MST
Serafino,
What you present here, between Einstein and Bohr, looks to me as
another example of a Bayesian versus a non-Bayesian point of view in
science. In particular, the difference between our knowledge of
reality, and reality itself.
The Copenhagen interpretation is a muddy mess. No wonder I didn't
understand it well in college, and it still bothers me now. Quantum
theory is successful, but, as Feynman says: "Nobody knows how it can
be that way."
Let's try to look at quantum physics from a Bayesian point of view.
I'm following Edwin Jaynes' writings, BTW:
Edwin Jaynes Probability
http://bayes.wustl.edu/etj/node1.html
These papers are good: "Probability in Quantum Theory",
"Clearing up Mysteries- the Original Goal".
Plus this one,
"Role and Meaning of Subjective Probability: Some Comments
on Common Misconceptions."
from here:
Giulio D'Agostini - Probability and Statistics
http://zeual1.roma1.infn.it/~agostini/prob+stat.html
(and this one too.. some parts in Italian:)
Quantum Mechanics and Probability
(+Confidence Intervals)
G. D'Agostini -- 18/01/2000
http://zeual1.roma1.infn.it/~agostini/clw_qm.html
Einstein was looking at the realities of nature, describing at an
*ontological* level.
>At that time Bohr has already developed his 'complementarity'
>principle [...]
>Heisenberg (and perhaps also Bohr) thought that the 'general'
>complementarity principle and his 'special' uncertainty
>principle had something to do with the concept of 'information'.
And Bohr was thinking on the *epistemological* level, not describing
reality but, instead, information about reality.
Bohr said: "There is no quantum world. There is only an abstract
quantum physical description. It is wrong to think that the task of
physics is to find out how nature _is_. Physics concerns what we can
say about nature."
Difficult to untangle, hmm? In his statement, he is stressing the
information processing aspect of science. Although Einstein and many
physicists would disagree with him and say that science is about
learning what is reality, and what are its 'laws', Bohr is pointing
out that any theory about reality can have no consequences testable
by us, unless that theory can also describe what humans can see and
know.
>Against Einstein's objection, Heisenberg and Dirac and Pauli
>emphasized that the 'wave function' did not represent a course
>of events in space and time, but it did rather express just our
>'knowledge' of the events. Einstein did not agree.
Neither Einstein nor Bohr was wrong. They were each describing a
different aspect of the problem.
If one incorporates human information into science, i.e. the
original "logical inference" as described long ago by Bernoulli and
Laplace, the quantum mechanical mud becomes clearer. For example, the
quantum mechanical probabilities involved in the EPR scenario became
Bayesian probabilities.
>But that is not the end of my story. It's interesting to note
>that Heisenberg (but not Bohr) believed that the 'collapse' of
>the 'wave packet' (thus also those 'spooky' actions) was _indeed_
>a physical action, triggered by the 'indivisibility' of the particle
>(The Physical Principles of the Quantum Theory, Un. Chicago P.,
>page 39). Was he right ? It seems so.
This is so muddy!
Here Heisenberg is mixing up realities of Nature, with incomplete human
information about Nature.
argggghhhhhhhhhhhh!!
(no further comment)
Amara
********************************************************************
Amara Graps, PhD email: amara@amara.com
Computational Physics vita: ftp://ftp.amara.com/pub/resume.txt
Multiplex Answers URL: http://www.amara.com/
********************************************************************
"Take time to consider. The smallest point may be the most essential."
Sherlock Holmes (The Adventure of the Red Circle)
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