Introduction: The Return of the
Aether
Nicht wie die Welt ist, ist das Mystische,
sondern dass sie ist.
(It is not how the
world is that is mystical, but that it is.)
Ludwig
Wittgenstein
Tractatus Logico-Philosophicus
Most of theoretical physics
in the twentieth century can be characterized by a reductionist attitude that
has revealed a hierarchical structure of the physical world. However, instead of being
"radically" reducible to one "basic" level only, each layer
of the hierarchy has turned out as largely autonomous. The great success of this approach consists
in a huge amount of often very precise knowledge about each of these layers,
unified in the "fundamental" descriptions via "universal"
laws. The successful strategy of
reduction and unification is due to a quite remarkable level independence, such
that, for instance, the effective Lagrangian on the level of molecular
interactions is for all practical purposes decoupled from the one on the level
of quarks constituting the molecules' individual nuclei.
However, level independence
is not only a "fact of nature" that we observe; it is also to some
degree a consequence of the reductionist strategy per se [Primas 1983], which
actively closes its eyes upon other, level connecting phenomena, like
self-organization, emergence, etc.
According to Sam Schweber, "it is not enough to know the
'fundamental' laws at a given level. It
is the solutions to equations, not the equations themselves, that provide a
mathematical description of the physical phenomena. 'Emergence' refers to properties of the solutions - in
particular, the properties that are not readily apparent from the
equations" [Schweber]. Thus, one
can say that toward the end of the twentieth century, physicists, and
scientists in general, although (necessarily) still remaining
"reductionists" in a weaker sense, increasingly tend to direct their
attention from level independence toward "holistic" phenomena. This is done in very diverse areas such as,
e.g., quantum theory (where holism has - "philosophically" - always
been an issue, but in recent years has also become of operational importance),
or the transdisciplinary study of self-organized
criticality [Bak et al.].
In general, holistic
phenomena cannot be described by linear, monocausal reasoning. Rather, whichever element on some particular
level is chosen for investigation, it must be considered in its context
involving other levels, with circularly causal relations between them. Contextuality and circularly causal (or
feedback-based) reasoning nowadays can be found in practically all fields of
knowledge. Although not always
explicitly stated as such, in practice they are a matter of course in the
humanities, as in sociology or psychology.
In evolutionary biology, one speaks of "evolutionary
landscapes" (e.g., in "fitness space"): if classical Darwinism
today resembles the study of the flow of a river's water by tracing the
trajectories of individual droplets back to their origins, the new systemic
approach to evolution has to consider also the river bed and the constant
interactions between the "water" and its surroundings. In other words, there exists a circularly
causal relationship between the trajectories of individual evolutionary units
(such as species) and their surrounding ecologies. A very similar systemic relationship can be found on the level of
the genes: Formerly having been considered as constituting the "atoms of
heredity," genes now are rendered to assume new roles within
"autocatalytic networks" [Kauffman].
Even in the physical
sciences of "inanimate matter," contextuality and circular causality
abound. For example, in General
Relativity, a massive body influences the spacetime curvature of its surroundings,
and vice versa: the curvature of spacetime determines the trajectories of the
massive bodies. Moreover, in the
Maxwell-Lorentz theory of the electron, particles and field mutually influence
each other. Furthermore, in
energetically open systems, processes of self-organization are characterized by
a mutual relationship between the dynamics of individual entities and the
boundary conditions of the whole system.
So, if the context of a research topic is not chosen too narrowly, circular causality is state-of-the-art, even in the (classical) physics of matter. But what about quantum theory? Apparently, this seems to be the only field of physics where causality is seriously questioned, and with respect to local monocausal explanations this is certainly justified. However, it is also justified to enquire whether the behavior of quantum systems really differs so much from all the other systems studied in the sciences. On the contrary, I shall try here to indicate the use of systemic thinking in quantum theory as well: the key issue will be contextuality and a circularly causal, i.e., a cybernetic viewpoint.
There may be several
reasons why such an approach has not been considered extensively so far.2 One of them is certainly given by the many successful
applications of quantum theory without any serious need for refined
viewpoints. Moreover, the implications
of the quantum phenomena may also be seen as being so radical for our whole
understanding of the material world we live in, that it may well take at least
decades to fully realize them. In fact,
the development of quantum mechanics in the twentieth century does show a
steady increase in awareness of its central feature, i.e., of nonlocality.3 While Albert Einstein referred to the
corresponding phenomena only as a "spooky action at a distance," John
Bell was able to show that no local hidden variable model whatsoever can
reproduce the predictions of quantum mechanics. Rather, quantum mechanics violates his famous inequalities which
are today named after him4 [Bell]. Later, Alain
Aspect's group [Aspect et al. 1982a, Aspect et al. 1982b] was the first to
experimentally verify the violations of Bell's inequalities (although with a small
caveat, later to be overcome, as mentioned by [Zeilinger]), and nowadays a
whole series of experiments makes direct use of the nonlocal nature of quantum
theory [Aspect].
In other words, during the
last decades of the twentieth century we have become witnesses of what I call
"the end of the twentieth century atomism," i.e., the end of
"the belief (put into practice with the atom bomb, nuclear reactors, or
particle accelerators) that the world, in its deepest essence, is composed of
tiniest entities - these 'atoms' today being some kind of 'elementary particles'
- such that any object can be considered, at least in principle, as a spatially
limited collection of a finite number of such entities" [Grössing
1993a]. In contrast, it has become
feasible to speak about dynamical "holistic" networks where
"particles" are embedded in a relevant (i.e., irreducible)
environment or "context." In this regard, I have already mentioned
the demise of the concept of genes as the "atoms of heredity" above,
giving way to the framework of autocatalytic networks. Similarly, atoms, electrons, neutrons, etc.,
which have once been considered as "fundamental particles," now have
to be described in modern quantum theory within the framework of nonlocal
holism, viz., the phenomenon of entanglement [Schrödinger 1935], for example.
This amounts to nothing
less than a "Copernican revolution" on the level of
"objects." Instead of being separate entities "centered in
themselves," - like some massive object with its gravitational field -
with the rest of the world somewhere around them, quantum "objects"
are not necessarily "centered" anywhere, but rather connected to
different and distant parts of the world that are simultaneously parts of the
quanta themselves. So, if we speak
about quantum "objects" at all, we must be aware that thereby we
already introduce a "de-finition" (or delimitation) that excludes
parts of the correlations of the quantum system with the rest of the world: as
Hans Primas has repeatedly pointed out, quantal "objects" do not
exist in an absolute sense, but only in a contextual one, i.e., in the
framework of our chosen delimitations.
In this sense, "observable phenomena are created by abstracting
from some EPR correlations" [Primas 1983, p. 253]. From ontological and epistemic points of
view, this has an interesting corollary:
According to quantum
mechanics the electrons of the moon are entangled with their radiation
field. If we are not willing to
abstract from the quantum mechanical structure of this radiation field on the
grounds that it is irrelevant for the problem under discussion, then the moon
becomes entangled with the sun, etc. and cannot be said to possess an
individuality. So without abstracting
from the quantum structure of the radiation field, the moon cannot be an object
[Primas 1983, p. 292].
... Nor can a single tree,
or a single electron, for example. Of
course, in our lives of daily routine, this does not change much - just as for
us the sun still "rises" in the east and "sets" in the
west, despite the heliocentric revolution of Copernicus and others. But if we are really interested in how the
world is, we have to face the "Copernican revolution" of quantum
theory in its full extent: that in its "deepest essence" (and as far
as we can talk about it today), there are no "atoms" of the physical
world separable from the rest; rather, the world has to be considered as a
whole, with "parts"
constituting only (more or less viable) simplifications of the actual ongoing
dynamics, or of what David Bohm has called the "holomovement" [Bohm
1980]. The fascinating perspective of
this new world view is, however, that under particular circumstances the
"wholeness" of the physical world can be used to show nonlocal
correlations that under our old atomistic perspective could only be qualified
as "magic." lt is clear that such a sweeping revolution literally
affecting our fundamental concepts of the whole universe cannot be fully
grasped within short periods of time, or be accepted by a scientific community
with firm roots in an "atomistic" world view to be overcome. This situation today is, in fact, very
similar to the cosmological "Copernican revolution" during the times
of the Renaissance, of which Alexandre Koyré has pointed out, that it, too, did
not succeed in one great step, but took decades, or even centuries to become
settled into the minds of individuals [Koyré].
I believe that the
"quantum revolution" still has not yet reached the full extent of its
meanings. For many physicists, for example,
the spectacular nonlocal correlations represent nothing more than the bizarre
outcome of calculations with quantum mechanical wave functions, which
themselves many consider as just symbolizing our knowledge of a quantum state. Of course, any symbolization is a mental
construct that only refers to a physical (or other) state, just as a map is not
a landscape itself. The crucial point
about the nonlocal correlations of quantum mechanics is, however, that here one
talks about physical processes with conspicuous simultaneous interdependences,
although they are miles (or further) apart.
So, in between Alice and Bob, who perform an EPR-type experiment and who
may be some 10 miles apart, there exists nothing but the vacuum. Entanglement, EPR correlations, and the
like, all refer to quantum systems, aspects of which are measurable at some
distant points A and B, with only the vacuum in between. Perhaps one should skip the word
"only" in the last sentence?
Perhaps the vacuum, rather than being "nothing," is a
"something" that does transmit information between A and B?
In fact, it has long been
known that the vacuum is actually a "plenum", rather than mere
emptiness. In a very definite sense,
then, it constitutes what has in earlier centuries been called the
"aether." This is also how Edmund T. Whittaker argues in the preface
of his History of the Theories of Aether
and Electricity:
As everyone knows, the
aether played a great part in the physics of the nineteenth century; but in the
first decade of the twentieth, chiefly as a result of the failure of attempts
to observe the earth's motion relative to the aether, and the acceptance of the
principle that such attempts must always fail, the word "aether" fell
out of favour, and it became customary to refer to the interplanetary spaces as
"vacuous"; the vacuum being conceived as mere emptiness, having no
properties except that of propagating electromagnetic waves. But with the development of quantum electrodynamics,
the vacuum has come to be regarded as the seat of the "zero-point"
oscillations of the electromagnetic field, of the "zero-point"
fluctuations of electric charge and current, and of a "polarisation"
corresponding to a dielectric constant different from unity. It seems absurd to retain the name "vacuum"
for an entity so rich in physical properties, and the historical word
"aether" may fitly be retained [Whittaker, p. v].
When Whittaker wrote this, neither the "Casimir effect" (to be discussed briefly in Section 4.4) was well known, nor were the whole physical implications of EPR-type correlations. So, the existence of an "aether" today is well established, and I shall use the word further on, even though for said historical reasons many physicists are not willing to do so. However, to do more justice to history, the concept of the aether actually has had some proponents even among twentieth century physicists, and it is their work that major portions of the present elaborations are based on. I am referring to the de Broglie-Bohm interpretation of the quantum-mechanical formalism. lt has its roots in first attempts by de Broglie in the 1920s [de Broglie 1927], experienced a major boost in the form of two papers by David Bohm in 1952 [Bohm 1952a, Bohm 1952b], and since the late 196os is being worked on by an increasing number of physicists. Its main feature is that it represents a "realistic" (as opposed to "idealistic" or "Platonistic") interpretation of quantum mechanics, in the sense that it can give an ontological meaning to quantum systems, and quantum systems themselves are considered as consisting of localizable particles whose dynamics are governed by a holistic nonlocal wavelike field, sometimes called the "guiding (or pilot) waves," and sometimes the "quantum potential."
The main point, where the attempts on a quantum cybernetics presented here diverge from the modern de Broglie-Bohm versions, can be formulated by the explicit introduction of a circularly causal relationship between "particles" (which are here considered as nonlinear parts of waves) and their surrounding waves. The latter are not only "guiding" passive "particles" in quantum cybernetics, but also being actively "co-determined" by the "particles." It is clear from the present status of quantum theory that a complete picture of quantum processes must be able to give an account of what happens to an individual quantum system. As can be seen from the implications of the Greenberger-Horne-Zeilinger experiment [Greenberger et al.], for example, a merely statistical interpretation of quantum mechanics is not sufficient any more for a full account: in this experiment, a single event can disprove any local hidden variable explanation or prove the nonlocality of quantum theory, respectively. So, quantum cybernetics is also an attempt at the construction of a theory of individual quantum systems. Of course, the statistics and the many-particle properties must be derivable from the theory, too. When I speak about "circular causality," it must be clear that this refers to just a single quantum and its surroundings, with which it has this form of causal relationship. In the case that more than one particle are involved, then, of course, we are faced with several "circular causalities" that actually cannot be separated into individual circles. These, then, rather represent a "web" of interdependent, mutually causal processes, which one could also term "holistically causal." However, in the present work, I shall retain the term "circular causality," mainly to illustrate the mutual relationship between "particles" and waves, even though in many actual situations a simple circle will not suffice for a complete description of the causal web involved. Nevertheless, causal circles are considered here as the essential dynamic "units," which define the organizational properties of quantum systems of whatever complexity.
This
book is structured as follows. In
Chapter 1, some of the problems concerning the compatibility of quantum theory
and the special theory of relativity are discussed. It is shown that a hitherto ignored consequence from the
principle of relativity has a wide range of implications even for the quantum
domain. Specifically, it is shown how
upon the assumption of a relativistic "aether," both Born's rule for
calculating probabilities of events and nonlocal correlations follow from the
principle of relativity. Although not
necessarily based on the idea of quantum cybernetics, but in perfect agreement
with it, a calculation scheme is presented with which the results of quantum
theory can be obtained without invoking complex-numbered "probability
amplitudes." A brief review of the de Broglie-Bohm interpretation of quantum
theory and problems concerning relativistic formulations thereof rounds up the
first chapter. In Chapter 2, the
approach of quantum cybernetics is presented, i.e., the idea of a circular
causality between waves and "particles." A relativistic quantum cybernetics
is proposed that can avoid problems of other relativistic formulations of the
causal interpretation. Furthermore, it
is shown how the rules to calculate probabilities in quantum theory can be
understood in principle. Chapter 3
presents a discussion of experiments relevant for the approach of quantum
cybernetics. In particular, it is shown
how superluminal velocities and perhaps even signaling might occur. With regard to special relativity, a
solution of an apparent conflict between different observers' descriptions of
nonlocal effects is given within a realistic framework, as well as a discussion
of "causal paradoxes" associated with eventual superluminal
signaling. In Chapter 4, Einstein's equations
for the gravitational field are derived from quantum cybernetics, thereby
providing a close link between circular causality at the quantum level and
Mach's principle. Finally, in Chapter 5, circular causality at the
quantum level is discussed, both with respect to the historical context and
future perspectives.
To complete this introduction, I want to point out
what this book is not about. Although
the term "cybernetics" may evoke associations with computing devices
in the reader, I do not deal with the field of quantum computing here. Also, the recently increasing interest in
controlling the performance of quantum precision experiments by using feedback
processes against decoherence effects [Anderson, Dunningham et al.] is not
covered. With the latter being rather
of the type of a "quantum control theory," I would like to reserve
the term quantum cybernetics for the proposed feedback processes constituting
any quantum system. Finally, let it be
said here that I have no intention whatsoever to propose an
"alternative" to quantum theory.
Cybernetics, as I understand it, is a way of looking at things, with a
particular focus on feedback processes that are describable as circularly
causal ones. This does not mean that
any description via the usual linearly causal approaches must be wrong. In effect, we know that quantum systems are
to be seen holistically, and any type of description, which by its very nature
is "reductionist" to some degree, will be only of some limited
value. Still, I hope to be able to show
that some central issues of quantum mechanics can in fact be illustrated very
aptly with cybernetic concepts. In
particular, the establishment and changes in nonlocal correlations shall be a
primary focus of my explorations. Thus,
quantum cybernetics is quantum theory from a cybernetic point of view.
Actually, quantum theory is so complex and rich of
curious phenomena that, to grasp it fully, no single canonical theory could
highlight all its features optimally.
In this sense, quantum cybernetics is an attempt to draw attention to
some aspects of quantum processes, which may explain some central questions of
today's theory, but simultaneously opens many new ones.
2 Exceptions discussing
different aspects of a hypothesized quantum "control theory" include [Guerra
and Morato, Santamato, Rosenbrock, MacGregor, Yasue].
3 In general, I refer to
"nonlocality" in the sense that spacelike separate regions of
spacetime are correlated or can influence each other. I will thus retain this nomenclature even in the case where
superluminal propagations are made responsible for the experimental results,
which one might then consider as elements of a "local" but
"holistically" causal theory.
4 Naturally, the remaining proponents of locality insist
that there are a few holes in the present experimental evidence [Selleri], but
the latter will most likely soon
be filled.