Original Source
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The Philosophy of Niels Bohr
H. Folse
May 1, 1985
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[This review by
Dan Glover
of Folse's 1985 book supports analysis of Professor Schombert's
lectures on 21st century science, specifically
complementarity,
reported on March 12, 2004. Folse's new book
Niels Bohr and Contemporary Philosophy (Boston Studies in the Philosophy of
Science) by J. Faye (Editor), H. Folse (Editor)
an updated version is available from
Amazon.com]
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The Early Years
Niels Bohr's theory of complementarity was developed over 70 years ago. He
abandoned his model of the atom 1926, and yet it is still the way the atom is
illustrated today in textbooks and on the internet. Complementarity never grew
into other disciplines of science like biology as Bohr envisioned, and yet it
is the underpinning of quantum theory and the way we view reality to this day.
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In the introduction, Folse writes:
"Certainly of all the developments in twentieth century physics, none has
given rise to more heated debates than the changes in our understanding of
science precipitated by the 'quantum revolution'. In this revolution, Niels
Bohr's dramatically non-classical theory of the atom proved to be the
springboard from which the new atomic theory of the atom drew its momentum.
Furthermore, Bohr's contribution was crucial not only because his
interpretation of quantum mechanics became the most widely accepted view but
also because in his role as educator and spokesman for atomic physics Bohr was
very much the patron spirit of the entire quantum revolution. The conceptual
framework which he proposed to provide a new viewpoint for understanding the
quantum theoretical description of atomic systems became for most of this
century the dominant outlook of countless productive experimental and
theoretical physicists. He called this new framework complementarity". (Pg. 1)
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Bohr invented the word 'complementarity' to convey the meaning of something
containing many truths. Interestingly, Buckminster Fuller uses the word
'complement' to describe the outside of a system in his angular topography
outlined in Synergetics. I am still not sure if they are talking about the
same thing or not, though I suspect that either idea, if it doesn't already
contain the other, can certainly be extended to.
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Folse begins his book by examining the history of quantum physics. All the
usual suspects are there and anyone familiar with quantum theory will feel at
home immediately. Bohr's chief rival became Albert Einstein, and over a period
of many years, the two engaged in a series of 'thought experiments' designed
by Einstein to show the fallacy of Bohr's theory of complementarity.
"The immense influence of Bohr's complementarity viewpoint, as evidenced not
the least in the historic debate with Einstein, naturally suggests asking why
complementarity has been the subject of such frequent misinterpretations.
Several distinct reasons probably contributed to the most important
misunderstandings." (Pg. 24)
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Many of Bohr's ideas are things we learned in grade school and are so much a
part of our thinking that we never even question where those ideas came from.
However, as the story goes on, we will see...
"First...Bohr often misused key terms in his arguments. He was not well
trained in the vocabulary or the problems of traditional philosophy and thus
did not always understand how his assertions would sound to readers who did
not share his outlook. Furthermore, partially due to the uniqueness of his
position, he often adopted a less than self-evident idiosyncratic expression
to refer to a crucial point. Although from youth he was indeed keenly aware of
what would normally be called 'philosophical problems', as we shall see in the
next chapter, the formative influences which shaped his outlook cannot be said
to have included any strong allegiance to a particular philosopher or school
of thought." ( Pg. 24-25)
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"Second, the nature of Bohr's writings did not lend itself to the
presentation of his framework in any systematic detailed fashion. All of his
philosophical work involves short essays, generally intended for public
delivery to large audiences with diverse backgrounds. His three philosophical
books are simply collections of these essays.
"Third, there were historical factors entirely out of Bohr's control that
created a climate conducive to misunderstanding complementarity. Not the least
of these was the fact that during the period of Bohr's philosophical work,
most of those competent to write on the philosophy of physics were committed
to some form of 'positivist' philosophy of science...a circumstance which was
hardly conducive to the best understanding of complementarity." (Pg. 25)
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"The dominance of positivism in philosophy of science also suggests a fourth
source of misunderstandings. Bohr certainly believed the atomic system was an
independently existing physical reality; he regarded physics as an attempt to
gain empirical knowledge about those entities. His point was that we cannot
describe these systems like classical physics described planets and billiard
balls...because of Bohr's 'partial' agreement with the positivists in opposing
classical realism, it is not unlikely that their influence was a factor in his
reluctance to explore the ontological consequences of complementarity." (Pg.
25-26)
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Many of Bohr's ideas were founded on positivist assumptions as well from what
I can tell of my readings. That is certainly to be expected as he was first
and foremost a scientist. Bohr strove for clarity and followed many different
paths searching for it.
Chapter 2 fills the reader in on Bohr's philosophical background with a
biographical sketch. He was born October 7, 1885 in Copenhagen. His family was
well represented in the Danish educational circles, his father being a
professor of physiology. He had an older brother, Harald, who carved out an
international career in mathematics.
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Folse writes: " Culturally Denmark stood midway between British and German
traditions, allowing in a real sense a fortunate synthesis of British
experimental science with the more formal, theoretical approach of the German
Universities. In many ways, Bohr's philosophical temperament combined British
influences stemming from the Lockean tradition of common sense empiricism with
the typically German heritage of Kantian concerns with subjective and
objective aspects of language. With respect to his philosophical development,
Bohr's Danish heritage allowed him a certain freedom from the overruling
'schools' of idealism and materialism closely identified with various national
traditions." (Pg. 32)
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This reminds me a great deal of Pirsig's exploration of how Native American
culture has permeated the culture of the white Europeans who settled here. Up
until 1940, Denmark was a neutral country where the most intelligent minds in
the world could meet and discuss static ideas in a Dynamic environment. Its
also interesting that even today, the cutting edge research is being done in
neutral countries.
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The Como Papers
In 1912 Bohr produced a series of 3 papers which outlined his new theory of
the atom and applied the postulates of his model to the formation of atomic
spectra. Folse writes:
"Bohr's fundamental atomic theory appeared in three parts in 'The
Philosophical Magazine' through the summer and fall of 1913. (Pg. 34)
...Through the ten years following his original 1913 papers Bohr continued
with the help of his assistants to extend his theory of atomic structure by
applying it to the entire periodical table. The last part of this great work
was added in 1922. That year marked a fundamental change in the nature of
Bohr's activities..." (Pg. 35)
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"Bohr who had met with considerable criticism and lack of understanding, had
at this time become one to whom all listened with reverence, so that the
discussion about the lectures were rather concerned with whether Bohr had
meant this or that, than the matter itself..." (Pg. 35)
Bohr was awarded the Nobel Prize in physics in December of 1922. Through the
1920s, he moved into his role as Director of Bohr's Institute at the
University of Copenhagen. Complementarity was first revealed to a public
audience in September, 1927, at a congress in Como, Italy. Folse writes:
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"The delivered paper was far from finished form. Most of the audience were
unimpressed, finding Bohr's argumentation far too 'philosophical' and
including nothing new in physics..., however, throughout the fall of 1927 and
the spring of 1928, the manuscript went through repeated rewritings. Finally
it was ready for print by Easter of 1928."
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These papers came to be called the Como Papers, and outlined Bohr's
complementarity. Einstein's negative reaction was a grave disappointment to
Bohr. Bohr made vital contributions to the theory of nuclear fission in 1939.
In 1943 he was forced to flee the University of Copenhagen because of Nazi
occupation.
After the war, Bohr became a world spokesman for nuclear and atomic physics.
Throughout the last 25 years of his life, Bohr pursued the theme of
complementarity as an epistemological lesson into a variety of fields. On
November 18, 1962, Bohr died in his sleep while taking an afternoon nap.
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Folse writes: " Bohr's manner of working was so distinctive that it has
received much comment in the memoirs of those who worked with him. Typically,
at the beginning of any project, Bohr started with the intention 'to write a
little paper on it'. This would be accomplished by his dictating, often in a
mixture of English, Danish and German, to a student or co-worker (or, in
earlier days to his mother or wife) sentence by sentence the text of the paper
to be. Sometimes there were long interruptions either for pondering what was
to follow, or because Bohr had thought of something outside the theme which he
had to tell me about." (Pg. 40, Oskar Klein- scribe/respondent for the Como
Papers.)
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As for Bohr's early philosophical influences, Folse writes:
"Thus I would conclude that if any philosopher other than Hoffling is to be
given credit for having shaped complementarity, that credit belongs to William
James. Through James the influence of Renouvier and Boutreaux, both of whom
James greatly admired, could be said to have had a third hand on Bohr's
thought, but it is likely that Bohr himself was never aware of this." (Pg. 51)
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Chapter 3 is called 'Quantum Theory and the Description of Nature'. Folse
explores Bohr's early thinking and the emergence of ideas that would lead to
his complementarity. In this chapter, Folse follows Bohr's intellectual course
from 1911 through 1927. Folse writes:
"Without exaggeration we may say that the framework of complementarity which
Bohr proposed in 1927 was the result of work on atomic theory which he began
as early as his doctoral dissertation in 1911...Bohr understood the
fundamental task of atomic physics to be accounting for the properties of the
chemical elements in terms of atomic structures....Because Bohr's
revolutionary atomic theory required a dramatic break with classical theory,
it is necessary to pause briefly to review how classical mechanics described
the behavior of physical systems."
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"As an empirical science, mechanics must of course develop a set of concepts
for describing what will be observed in specific circumstances. Since motion
is a change of position through time, for a science of mechanics what needs to
be observed is only the position of bodies at instants of time, and the
subsequent change of these positions through time relative to some reference
system. Since the term 'body' refers to those objects whose behavior is
described in mechanics, it follows by definition that bodies must possess the
properties of position at each instant throughout a temporal duration, as well
as the ability to change these positions. A 'physical system' may then be
defined as any group (including possibly one) of such bodies." (Pg. 57)
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"Mechanically the simplest possible system would be a single body system
whose position could be represented as at rest or moving in a straight line at
a constant velocity (uniform rectilinear motion) relative to some reference
system...But of course mechanics cannot provide descriptions of only single
body systems whose motion does not change. Real physical systems consist of
more than one body and of bodies not at rest or in uniform rectilinear motion.
The cause of departures from such motions is defined as a 'force'."
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"Though not visible or impenetrable like material bodies, fields are defined
as existing over a spatial region and manifesting a force at each point in
that region. Thus in classical electrodynamics light and other forms of
electromagnetic radiation can be theoretically represented as a wave
disturbance moving in an electromagnetic field, commonly analogized to the
motion of waves across the surface of a liquid." (Pg. 58)
"A mechanical description of the interactions between matter and radiation
could be expressed in terms of an exchange of energy between bodies and the
field...thus within the classical framework, the concepts of 'particle' and
'wave' refer to the theoretical representations through which one describes
the behavior of matter and radiation."
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This is how we can describe everyday reality. When the microcosm is examined
however, the clear distinction between particle and wave no longer exists. It
was discovered that both the particle and the wave theory worked equally well
in describing the nature of the photon, where our notions of space and time no
longer apply.
Folse writes: " Bohr's adaptation of the quantum postulate was completely an
ad hoc addition to the classical framework with which it sharply conflicted.
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"As long as the system remains closed, if we know the state parameters of
each component in the system at some point in time, the 'initial conditions',
then the law of mechanics, when applied to the state of the system, permit one
to define the state of the system at any future time...The conservation
principles for momentum and energy are thus what make possible defining the
future states of a system by applying the classical principles to its state at
some initial moment." (Pg. 59)
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"From 1913 when Bohr published his atomic theory until 1925 when Heisenberg
and Schr”dinger succeeded in formulating consistent theories, Bohr
relentlessly followed his general program of extending his early conception of
atomic systems to explain all experimentally observed properties of the
chemical atom. However, because of its internal inconsistencies he knew from
the start that his theory could not provide the ultimately satisfactory
description of atomic systems...and it remained a primary source of criticism
for those who continued to regard Bohr's theory as solely a heuristic device
for predicting a variety of phenomena, not a description of what really goes
on inside atoms." (Pg. 66)
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Throughout this period, Bohr stressed himself against taking his model as a
literal picture of the atom. Bohr felt that a new framework for describing the
atomic system should focus on the fact that quantum description of the
interactions taking place at that level must tend to correspond to classical
description. This so-called 'correspondence principle' allowed Bohr's theory
to be expanded in many ways.
In 1924 Bohr wrote A.A. Michelson: "...it appears possible for a believer in
the essential reality of the quantum theory to take a view which may harmonize
with the essential reality of the wave conception...[and] it seems possible to
connect the discontinuous processes occurring in the atoms with the continuous
character of the radiation field in a somewhat more adequate way than hitherto
perceived." (Pg. 76)
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Harmonizing Quantum Description
During this time Bohr was searching for a way to harmonize the quantum
description of the atom with a belief in essential reality of waves-in-a-field
representation of radiation. The price to pay for this harmonizing would be
the abandonment of strict energy conservation in individual interactions. If
abandoning energy conservation was the answer, then the quantum description of
the atom as changing its state discontinuously could be understood as a true
representation of essential reality.
Comment from Doug Renselle: From what I can tell, energy conservation is a
SOM nonstarter. Vacuum Energy (non)Space is so dense that it has enough
energy in 1 cubic centimeter to make
~100,000,000,000,000,000,000,000,000,000,000,000,000,000 of our known
universes, give or take a few zeroes. If we retain the concept of energy
conservation, it, as SOM, must be kept in a small, subsumed portion of our
new theory.
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Bohr writes in late 1924: " After all, I believe that there may be more
truth to the pseudo-mechanical treatment I tried in old times than one might
perhaps think. In fact I believe we have here to do with an instructive
example of the limitations in ordinary quantum theory rules...which affords
an illustration of the necessity of giving up the strict validity of the
general principles of conservation of energy and momentum." (Pg. 76)
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However, 5 months after this was written, Walter Bothe and Hans Geiger of
Germany demonstrated that energy was indeed strictly conserved in individual
atomic interactions, thus disproving Bohr's proposal. On the very day he
received news of this experiment, Bohr wrote:
"...it seems therefore that there is nothing else to do than to give our
revolutionary efforts as honorable a funeral as possible...In fact I think
that the possibility of describing these experiments without a radical
departure from an ordinary space-and-time description is so remote that we
may as well surrender at once and prepare ourselves for a coupling [i.e., an
interaction] between the changes of state in distant atoms of the kind
involved in the light quantum theory...I am thinking of all kinds of wild
symbolic analogies." (Pg. 77)
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Comment from Doug Renselle: See remarks above. My interpretation, given
today's knowledge, is nonspace (DQ) can add to and subtract from total
static (SQ) energy in space. Just prior to the big-bang quantum/Quality
event, space was without static (SQ) energy or matter (they are identical
by E=mc^2). Just after BB event, space became static (SQ) energy embedded
in its parent, the isotropic dynamic energy we call nonspace or DQ. Today,
supernovas and black holes, et al., add and subtract respectively to and
from space's static (SQ) energy. If I am right, there is no way nonlocal
space energy may be conserved. Clearly, it changes over time.
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This gives an idea of Bohr's thoughts as he realized that harmony was not
achieved because it was impossible to abandon strict energy conservation
at the atomic level. First, since energy is conserved, the description of
the interaction between matter and radiation could not represent radiation
in these phenomena as a continuously changing field. Thus he suddenly took
light-quantum theory much more seriously.
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Doug Renselle: My description above is cosmological. But if you read
Feynman, et al., they speak of virtual particles, tunneling, BECs, etc.
Maewan Ho shows us that our muscles are coherent zero-entropy,
non-thermalized energy consumers. Clearly, flexing your arm uses
DQ/nonspace energy in a coherent process. Probably mind does too.
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The other aspects of the classical ideal for a description (space-time)
also became suspect. Consequently Bohr began to consider the possibility
that theoretical representations of isolated atomic systems through the
'picture' of a system of particles moving on definable trajectories and
of radiation in free space as a wave moving through a continuous
electromagnetic field could not be understood in a classical sense of
systems to be described.
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Wave/Particle Dualism
Once Bohr realized that matter/energy conservation could not be given
up, he also realized that the dualism of particles and waves would be
something his new framework would have to deal with. It was during this
time that Bohr had intense, almost daily discussions with a young
assistant named Werner Heisenberg.
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" ...it comes as no surprise that Heisenberg recalls in their
discussions during the spring of 1926, Bohr reluctantly agreed for the
first time to completely abandon any attempt to describe the atomic
system in terms of 'visualizable' or pseudo-mechanical models. Here
'visualizable' clearly refers to 'space-time description' as classically
understood. Nevertheless, it is probable that the parties to this
agreement had rather different interpretations of what had been agreed
to. On the one hand, Heisenberg apparently read their agreement as
Bohr's endorsement for pursuing a purely mathematical theory that would
ascribe properties only to observed phenomena resulting from
interactions between atomic systems and radiation. On the other hand,
Bohr characteristically read this agreement as endorsing a search for a
revised understanding of how we use space and time concepts in picturing
the behavior of atomic systems. For Heisenberg, this resolve helped to
produce first matrix mechanics, then some twenty months later, the
uncertainty principle. For Bohr, this agreement marked a major step on
the road to complementarity." (Pg. 78)
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Heisenberg saw Bohr's doubts about 'visualizable' models as implying
that theoretical representations of the atom should proceed without
attempting a space-time description of what is actually happening there.
Heisenberg felt that the theory should focus on simply predicting
results between radiation and atomic systems. Bohr was critical of
Heisenberg's disregard for describing the physical aspect of the atom.
"'I was completely shocked', recalled Heisenberg; 'I got quite furious
because I thought I had something real and now they tried to explain it
away'. So we had quite a heated discussion but at the end I came out
with a slight victory...And I had for the first time the feeling that
now I had been able to convince Bohr about something about which we had
disagreed." (Pg. 79)
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The Uncertainty Principle
In the summer of 1925, Heisenberg succeeded in formulating matrix
calculus, the first expression of the 'new' quantum mechanics and a
theory that completely eradicated any dependence on space-time
descriptions of the atom. This success led Bohr to determine the exact
point where the classical descriptive ideal broke down, and ultimately
led to his theory of complementarity.
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However, the highly abstract nature of matrix calculus seems to bar the
way to finding any physical interpretation of the mathematical scheme.
Thus Heisenberg's achievement led Bohr to analyze the relationship
between the empirical classical system and the meaning of those same
concepts within quantum representation of the atom.
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When matrix mechanics appeared, both particle and wave representations
seemed necessary to describe the full range of phenomena observed in the
atomic system. However, if these theoretical representations applied to
'real' objects, then it would seem that these systems must have
contradictory properties. Bohr put this inconsistency into the 'dualism'
of particles and waves.
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In 1927, Heisenberg presented his Uncertainty Principle, and in April of
1927 Heisenberg and Bohr finally reached an agreement. Bohr wrote to
Einstein: "Heisenberg has asked that I send you a copy of the proofs he
expects of a new article which he hopes will interest you...it has long
been recognized how intimately the difficulties of quantum theory are
connected with the concepts, or rather the words, which are used in the
description of nature and all of which have their origin in classical
theory...This situation permitted us by the limitations on our
possibility of observations, in order to avoid all contradictions, as
Heisenberg stresses...Through his new formulation we are given the
possibility to harmonize the demand for conservation of energy with the
wave theory of light, while in accord with the nature of description,
the different sides of the problem never come into appearance
simultaneously." (Pg. 97)
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In this letter, Bohr outlines many of his arguments for complementarity
which would lead to its birth. Bohr is looking for a "limitation" which
would restrict the application of classical physical ideas when applied
to quantum theory. At the same time, Bohr maintained that these
classical notions must be maintained to describe the physical
interactions which the new theory treated as an "interpretation of the
experimental material".
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Bohr felt that "because if the objects described by quantum mechanics as
such waves and particles did in fact have independent reality in the
ordinary physical sense, it would be possible to define classical
mechanical states to them." (Pg. 111)
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Bohr concludes that space/time coordination and causal description are
complementary: "The very nature of the quantum theory thus forces us to
regard the space-time co-ordination and the claim of causality, the
union of which characterizes the classical theories, as complementary
but exclusive features of the description, symbolizing the idealization
of observation and definition." (Pg. 113)
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The argument presented in the Como Papers remained Bohr's approach to
complementarity throughout his life. This overview of complementarity is
now complete, and you may continue the review by following the links at
the bottom. Thanks for reading!
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The Framework of Complementarity
Part 1 - Overview Early Years Bohr Formulates Complementarity
Part 2 - Argument for Complementarity
Part 3 - Comments on Complementarity
Part 4 - Complementarity and the Uncertainty Principle
Part 5 - Refinement of Complementarity
Part 6 - Extension of Complementarity
Part 7 - The Nature of Empirical Knowledge
Part 8 - Complementarity and the Metaphysics of Quality