Inadequacies of Phenomenology
maxwell
Bokulich (a professor & student of the history of physics) makes some
very interesting points about how some of the 'quantum giants' viewed
realism vs instrumentalism (or phenomenology). I shall just focus
here on her second chapter that reviews Heisenberg's philosophy of
physics, as his position is often misunderstood.
Firstly, she challenges the widespread assumption that Heisenberg was
a naive positivist or instrumentalist (p. 30, 38). She makes the case
that Heisenberg explicitly rejected positivism & endorsed a version of
scientific realism. She documents how H believed that both classical
mechanics (CM) & quantum mechanics (QM) were BOTH realistic
descriptions of nature "in their own domains" based on his
metaphysical view that "nature itself is divided into various regions
of reality" (p. 34). She claims that throughout his writings,
Heisenberg is quite critical of phenomenological theories since "...
they do not give any real information about the physical content of
the phenomenon, about those things that really happen."
"Phenomenological theories are understood as just calculational tools,
theories that 'save the phenomena' while failing to give us any true
insight into nature." (p.39).
This ties back to the original programme of Natural Philosophy begun
by Newton (acknowledged by Heisenberg) & strongly adhered to by most
other earlier famous 'scientists' such as Clerk-Maxwell & gradually
lost through the 20th Century as American 'pragmatism' took over
physics. Interestingly, Heisenberg viewed the Ptolemaic system as a
phenomenological theory (as I do) & contrasted this with the realistic
Copernican/Newtonian theory (p. 43). I would make the point that
theoretical physics has failed to make progress whenever phenomenology
is in the ascendent - I can only hope that today this mistaken,
metaphysical view is reaching its zenith.
glird
><�I would make the point that theoretical physics has failed to make progress whenever phenomenology is in the ascendent - I can only hope that today this mistaken, metaphysical view is reaching its zenith.>
;-] !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
For a far better metaphysics try The Universe, by G Lebau,
maxwell
The lack of response to my first post on Bokulich's important book
perhaps indicates a deep level of sophistication amongst the members
of this NG or perhaps the term "phenomenology" was just a little too
philosophical for most. In case it was the latter, I will make
explicit the definition I am using: "phenomenology in science is used
to describe a body of knowledge which relates empirical observations
of phenomena to each other, in a way which is consistent with
fundamental theory, but is not directly derived from theory". In
particular, I was using it to refer to the use of mathematics alone to
define progress in theoretical physics, a trend that has come to
dominate our area in the last 50 years.
Nonetheless, I shall continue to encourage members to read Bokulich's
wel-written book by summarizing further chapters (penniless members
can get their own good idea of the book by accessing the 'LookInside'
feature on Amazon Books). Bokulich's third chapter focuses on Dirac
(in my view, the greatest theoretical physicist of the 20th Century)
but, like Heisenberg, one around whom many false myths have
accumulated. The first point to know (for those who have yet to read
any biographies of Dirac - Kragh's is the best), is that he started
out as an Electrical Engineer & this gave him an appreciation for the
power of approximation & one who (unlike Heisenberg) saw "physics as a
discipline much closer to engineering than as a set of consistent
axiomatic systems". Again, unlike his friend Heisenberg, Dirac viewed
"even the most well-established parts of quantum theory as open to
revision; indeed he takes no part of physics to be a permanent
achievement." <p. 49> Again, unlike Heisenberg & the rival German/
Danish approach, Dirac saw "QM as simply the generlization of CM to a
non-commutative algebra" based on the ANALOGY with the Hamiltonian
theory of CM. He did write, however, in 1945 that "the development of
the analogy has been greatly hampered by the mathematical methods
available for working with non-commuting quantities" <p. 54> (was this
a dig at the Schrodinger approach?).
The older Dirac got, the more he turned back to CM for inspiration (as
I do) as he became more disatisfied with the QED he had help create.
Dirac was not one of those those who think that agreement in the 14th
digit was a definitive validation of the renormalization programme,
like when he wrote <p. 59> "Just because the results happen to be in
agreement with observation does not prove that one's theory is
correct." In true Lucasian tradition he believed that any "branch of
physics formulated without equations of motion will remain
disconnected from the rest of physics" <p. 60>. Like Dirac, who
almost always thought in particle terms, I find it hard to think of
developing any such equation for a "wave" that extends over all of
space.
Bokulich makes the focus of this chapter <section 3.5> the demolition
of the popular myths that Dirac was not interested in the
interpretation of QM or that he sided with Bohr (& the Copenhagen
school) in the battle with Einstein over QM. The key evidence she
uncovers is an unpublished (& almost unknown) manuscript that Dirac
wrote at the end of his life favoring Einstein's deterministic views
<p. 67>.
Like Einstein, at the end of his life, Dirac also felt isolated from
the main stream & the pressure to conform to the consensus views in
physics <p. 70>. It is obvious that these pressures to conform are
even greater today, as some of my fellow 'older posters' are prepared
to admit.
(to be continued ...)
Maxwell
> ...
This series of postings will continue my summarization of Professor
Bokulich's recent book to illustrate my thesis that "mathematics
without interpretation is NOT physics".
Professor Bokulich's fourth chapter begins with a deliciously ironic
quote from Hamlet: "Something is rotten in the state of Denmark".
This is a suitable opening for a study of her demythogizing of the
standard 'Copenhagen' interpretation of QM, associated with Nils Bohr
& his allies. She shows how Bohr over-reacted to several failed
attempts in the early 1920s to extend Bohr's original theory ("Old
QM") to the helium atom, where the infamous 3-body problem once again
reared its ugly head, as it has since Newton failed with this simple
planetary problem <p.80>.The German school seized on this failure to
illogically propose that therefore electrons could not possibly
follow classical orbits (although this failure didn't stop the Moon in
its tracks!).
Rather than viewing the new QM as a revolutionary stage in the
development of physics (quantum leap?), Bohr is shown to have viewed
this as another continuous step from 'old QM'. Indeed, she shows how
Bohr viewed his "Correspondence Principle" (CP) as really a selection
rule - one that even applied to SMALL quantums numbers <p.88>. Bohr
saw the CP as the "deep link between CM, the old QM & the new QM,
tying all these theories together." <p.94>.
Bohr's insistence on using the "concepts of classical mechanics" (like
position etc) in QM arose from this evolutionary viewpoint.so that
"the application of these concepts alone makes it possible to relate
the symbolism of the <new> quantum theory to the data of experience."
<p.98> In other words, it was not just in the analysis of measurement
that classical concepts are essential. Nonetheless, the orthodoxy
still claims that electrons cannot possibly follow unique
trajectories. Or, as Professor Bokulich writes: "For Bohr, QM without
CM is an inadequate - even meaningless - theory." <p.101>.
(The denouement from all of this will have to await the next posting.)
Ilja
> This series of postings will continue my summarization of Professor
> Bokulich's recent book to illustrate my thesis that "mathematics
> without interpretation is NOT physics".
Nice series, thank you.
Ilja
Maxwell
Here's the final summarization of Professor Bokulich's important new
book - I will focus on chapters 5 & 6 on Semiclassical Mechanics (SCM)
leaving her final chapter for those specialists who are interested in
meta-theorizing in philosophy.
SCM is defined as "the theoretical & experimental study of the
interconnections between CM & QM". This was an area of physics that
has seen significant progress since the 1970s but one where I was
totally ignorant (my shame). The key idea is to blend the idea of a
particle's classical trajectory with an associated quantum phase.
This new area of physics provides intuitive insights into problems
where the quantum solutions are opaque, especially with respect to
"quantum chaos", like the helium atom or the hydrogen spectrum in very
strong magnetic fields, where the electron "appears" to be following
CM trajectories <p. 105>. These exciting results imply that Bohr's
"old" QM was not the 'dead-end' that the 'Young Turks' of QM believed
in 1925. SCM has also been used to analyze quantum dots, where their
experimentally measurable conductance properties depend on the
properties of the CLASSICAL electron dynamics <p.131>.
Several researchers in SCM (including me) are "reluctant to view these
trajectories as purely mathematical objects since they carry a lot of
PHYSICAL information about the classical & quantum dynamics" <p.137>.
This illustrates one of the central myths of QM, namely: "a classical
trajectory requires a simultaneously well-defined position & momentum"
which is supposed to conflict with Heisenberg's Uncertainty Principle
(UP). Of course, mathematicians never have to ask about the
ontological basis of physics as they are completely content with only
their equations. Physicists should welcome these significant new
results of SCM as it restores understanding and the power of the human
imagination (visualization) for creating new attempts (mechanisms) to
generate progress in theoretical physics, which has been stalled for
almost 50 years. Indeed, numerical solutions of Schrodinger equation
to all but trivial examples provide no understanding or insight,
leading only to the blind leading the blind. As Professor Bokulich
concludes: "There are striking affinities between Dirac's approach [to
physics] and SCM research" <p.163>.
I cannot encourage members enough to read this important book.
xray4abc
>
> - Show quoted text -
Well, it sounds interesting to me, as I do share similar ideas about
this issue. :-)
Best regards,
Laszlo Lemhenyi