From: Amara Graps (amara@amara.com)
Date: Wed Sep 11 2002 - 23:40:45 MDT
Responding to some things said by Dan Fabulich
(about Bohr.)
>With that said, Bohr's complementarity principle was explicitly
>subjectivist, though it did reify uncertainty: uncertainty under
>complementarity is a thing in the world (because the world is nothing
>more than our perceptions/measurements/observations).
According to Edwin Jaynes, 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."
So then here, Bohr 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. 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.
-------------------
(about Dirac.)
>I seem to think that Dirac was actually a positivist and rejected the
>whole notion of subjectivity/objectivity as a meaningless one.
I talked with Serafino about Dirac, I never had the good fortune to
talk with Dirac and listen to any of his lectures, but Serafino did,
so he had some idea what was Dirac's perspective. He said that the
late Dirac was certainly not a positivist, and the young Dirac was
probably not either. Quoting from him about Dirac:
<begin quote>
His credo was simple.
Imagine a mathematical structure,
try to write down an equation,
if the equation does not possess beauty
throw it away, and search another
beautiful equation. If the equation
is beautiful and meaningful it might also be "true".
Do not care so much about experiments.
<end quote>
and here are more notes regarding Dirac's perspective:
P.A.M. Dirac, The Development Of Quantum Mechanics,
Conferenza Tenuta il 14 Aprile 1972, Roma
Accademia Nazionale dei Lincei, 1974
(11 pages) [*]
P.A.M. Dirac, The Inadequacies Of Quantum Field Theory,
1984 (his last paper), in B.Kursunoglu & E.P.
Wigner (eds.) The Dirac Memorial Volume,
Cambridge U.P., 1987
[*] pag. 6
' This statistical interpretation is now universally accepted as
the best possible interpretation for quantum mechanics, even
though many people are unhappy with it. People had got used
to the determinism of the last century, where the present
determines the future completely, and they now have to get used
to a different situation in which the present only gives one information
of a statistical nature about the future.
A good many people find this unpleasant; Einstein has always
objected to it. The way he expressed it was: 'The good God does
not play with dice'. Schroedinger also did not like the statistical
interpretation and tried for many years to find an interpretation
involving determinism for his waves. But it was not successful
as a general method. I must say that I also do not like indeterminism.
I have to accept it because it is certainly the best that we can do
with our present knowledge. One can always hope that there will
be future developments which will lead to a drastically different
theory from the present quantum mechanics and for which
there may be a partial return of determinism. However, so long
as one keeps to the present formalism, one has to have this
indeterminism. '
----------------
Personally, I wish that Edwin Jaynes and Dirac could have gotten
together. They were not too far in their intellectual circles. Jaynes
worked with J.R. Oppenheimer studying quantum mechanics first at
Berkeley, then at Princeton (institute for advanced study). Jaynes'
thesis was to be on quantum electrodynamics, but Oppenheimer never
retreated from the Copenhagen position. So Jaynes changed his advisor
to Eugene Wigner in 1948, and finished his PhD thesis calculating the
electrical and magnetic properties of ferroelectric materials.
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/ ******************************************************************** "Dare to be naive." -- Buckminster Fuller
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