Some quotes from essays written by the physicist F David Peat. I became aware of him through reading his biography of David Bohm. He passed away last June.
"The prime mover of the Copenhagen Interpretation of Quantum Theory, Neils Bohr, took pains to stress the essential wholeness of quantum phenomena. As a direct result of the indivisibility of the quantum of action, each experiment or observation of the quantum domain must be taken as an unanalyzable whole. Bohr's interpretation of the quantum theory had the effect of introducing a radically new idea into science, for up to that time it had been natural to define material bodies in terms of their properties and, in particular, their locations in space. Their behavior was then described in terms of the various forces operating between them which caused them to move or change their states. But now Bohr was denying the validity of this whole approach for, at the quantum mechanical level, he argued, bodies in interaction form a single, indissoluble whole.
More recently this quantum holism has been underscored by the various experimental tests of Bell's Theorem. In essence they indicate that two quantum particles --initially in interaction but now well separated in space-- must be represented by a single inseparable state. This notion of this inherent inseparability has led a number of authors to argue that a basic non-locality is essential to a quantum theoretical description of nature.
Is this non-locality something that can be added to conventional quantum mechanics or is a radically different approach required? Is it possible to develop a description of non-separability within a purely local theory, or does non-locality represent a complementary form of description to that of locality? Could it be that the concept of space is far richer than physics has hitherto supposed, so that it contains a whole series of properties? And would this imply that physics should move to some deeper theory in which both locality and non-locality emerge as limiting forms?"
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"For well over two hundred years locality has been fundamental to our way of looking at the physical world. Indeed it is so deeply ingrained in scientific thinking that a non-local form of interaction appears, in Einstein's words, as "spooky".
A local description gives central position to the concepts of location and separation in space. Bodies are defined in terms of their spatial position and the trajectories they make. In turn, this description is founded upon the idea of a continuous manifold--a coordinate grid created out of dimensionless space (or space-time) points. Moreover, this manifold is supposed to exist prior to bodies and fields. Indeed it has an important ontological significance for, since the time of Clifford and Einstein there have been theoretical attempts to build fields and matter out of its geometry. A continuous space-time therefore becomes the ground out of which the entire physical world is to be built.
To reject locality would therefore be to throw away the full potential of this underlying manifold. In addition, physicists would be forced to abandon a whole range of rich and powerful mathematics. This latter action would, in itself, involve a major revolution in science. But the idea of locality goes even deeper for it pervades the whole of physics in an almost subliminal way. Indeed even the attempt to discuss non-locality runs into difficulties with the very language we speak. Terms like space, distance, location and separation have all become colored by several hundred years of thinking about space in a particular way. There does not even exist a word to describe the concept we are now exploring--except in terms of the negation of "locality". Locality has become so deeply ingrained in the thinking of physicists that it now seems impossible to abandon it."
(As the physicist Basil Hiley puts it, "physicists come to praise Bohr and decry Einstein, but end up paying only lip service to Bohr and thinking like Einstein." (i.e. their understanding of the full implications of quantum theory is vague and in their everyday science they still cling to classical ways of thinking.))
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"Despite the authority inherent in the locality of space-time, evidence is accumulating that it is an inappropriate way to describe quantum theory. Neils Bohr has called for a holistic approach to quantum phenomena, while Pauli and others felt that conventional concepts of space and time are inadequate for a quantum description. Current discussions of Bell's Theorem suggest that we may be forced to entertain complementary non-local descriptions-- although it may also be possible to develop purely local theories which forbid separability of certain quantum states.
To this must be added the notion of global quantum states. The wave function for a superconductor, and other condensed states, is defined over macrosopic dimensions. This suggests that a more natural description may involve what could be called a global rather than a local mathematics.
Elsewhere I have argued that quantum theory is characterized by the importance given to the overall form of the wave function, and this form is essentially a property of the whole system. An example of this would be the Pauli Exclusion Principle that demands an overall symmetry for a wave function that extends over all space. It is this global form, or symmetry, that plays a role in deriving Bell's correlations, for it dictates that the wave function cannot be spit into a simple product of independent terms associated with different locations in space. A global form, I have argued, is a general requirement of which the Bell theorem is only one example.
While Schrodinger's wave mechanics and quantum field theory are formulated using local mathematics based on an underlying continuous manifold of space-time points, there are powerful arguments suggesting that such a manifold can not have an actual physical existence. The energy content of small regions approaching the Planck length is so high as to break down space-time structure into regions of extremely high curvature or even into a space-time "foam". Clearly the notion of dimensionless points is incompatible with quantum theory. Does the answer lie in some modification of our current approach, such as replacing space-time points by extended objects like strings-- or is some more radical departure needed?"
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"The reality described by classical physics, Bohm suggested, a reality of solid, well-defined bodies with definite positions in space and a specific duration in time should be termed the Explicate Order. Much of what we perceive of the world is in the form of this Explicate Order. By contrast, the reality appropriate to quantum theory is one of superpositions, enfoldings, interpenetrations and a space that is non-local. Bohm referred to this as the Implicate Order. For the purposes of illustration Bohm pictured this implicate order in terms of images of a holograph, or a drop of dye being twisted into a fluid until it becomes totally enfolded. (But such metaphors are, in themselves limited and do not exploit the full implications of the Implicate Order.) Thus elementary particles could be thought of not as exclusively solid well-defined objects in space but rather as processes that unfold and enfold out of the entire universe.
Referring to the persistent inability of science to reconcile Einstein's theory of relativity with quantum theory, Bohm suggested that what was required was not so much new theories and ideas but a radical new order within physics. The Implicate Order would be such a new order. According to Bohm physics is still dominated by what he called the Cartesian Order. That is, an explicate notion of space and time which, in turn is expressed using Cartesian co-ordinates - every point in space-time being well defined and corresponding to a set of numbers. The considerable practical success of the Cartesian order lies in the fact that the motion and transformations of objects in space are describable by differential equations. By contrast, an Implicate Order would proceed via some different descriptive scheme, such as an algebra.
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"It was Bohr who argued that words like position, momentum, spin, space and time refer to classical concepts which have no place within quantum theory. Einstein for his part argued that it should be possible to develop new concepts that are more suited to the quantum domain. However Bohr maintained that, since our language of its very nature is grounded in our day to day commerce with the large scale world, it will not be possible to modify or change it in any significant way. In other words, an unambiguous discussion is only possible at the classical level of things, that is when it is about the results of quantum measurements made with laboratory scale apparatus. But to ask what actually happens at the quantum level of things makes no sense.
The changing meanings of words can also be seen in those terms which have to do with spatial relationships such as space, position, locality, non-locality and even interaction. They have undergone far reaching changes in the developments which led from the Aristotelian to the Newtonian and finally to the general relativistic and quantum mechanical picture of things. Yet because the same word "space" is used in each case it is possible to create the illusion that different scientists are sometimes talking about the same thing. Particular difficulties can also be found in discussions about the significance of Bell's Theorem and the meaning of non-locality in physics. Of course working physicists perfectly understand the difference between quantum theory, relativity and Newtonian mechanics, nevertheless there are many particularly subtle differences in meanings associated with a word such as space and it is often the case that the old and new meanings co-exist side by side. In other words scientists may employ the same word in subtly different ways within the same conversation. It is the actuality of our situation as human beings that we must employ language in order to communicate and, for this reason, we must pay careful attention to both the power and the limitations of language.
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"It was Neils Bohr who emphasized what he called complementarity in science. While this idea was first introduced with specific reference to the quantum theory, Bohr really felt that the idea of complementary had a universal application and extended to all forms of inquiry and knowledge. As Bohr put it, knowledge and the means of inquiry are inseparable. There is an essential wholeness to our investigations of nature, for the way we investigate things cannot be separated from the results we obtain. The genesis of this idea lies in the quantum theory where experimental results are dominated by Heisenberg's uncertainty principle and by the wave/particle duality. Ask a particular experimental question and nature answers in terms of waves, pose the question in another way and the result is in terms of particles. In the world-view of classical mechanics the concept of wave and particle are mutually exclusive and this too is the essence of Bohr's proposal--that the results of experiments on the quantum world are complementary or mutually exclusive.
Bohr believed that complementarity had a universal application and, in particular, it applied to biology and psychology. No matter if the means of inquiry are experimental, theoretical, philosophical or linguistic they are always inseparable from the nature of the answers we obtain. Investigate any system of sufficient subtlety by different routes and one will obtain complementary answers.
Complementary viewpoints will, therefore, be particularly apparent when biologists and theoretical physicists meet together, and if scientists are to have a deep influence on each others ideas then they must be especially sensitive to the complementary nature of their approaches and have the necessary intensity to engage in a truly creative dialogue together.
Another feature of these complementary approaches is that ideas and concepts, which on the surface may sound very similar, are associated with different meanings and are used in quite different contexts by physicists and biologists. The result can be the sort of linguistic confusion that the philosopher Wittgenstein spoke about. There is a danger of engaging in long and fruitless debates of great intensity, in which the parties emerge confused and frustrated because their views do not seem to have been taken seriously [...] Once again physicists and biologists must be especially sensitive in their dialogues together, that they do not become trapped in a maze of their own construction.
How then will it be possible for new concepts, ideas and approaches to evolve through this overlap and union of quantum theory, biology and the philosophy of cognition? In the case of the present meeting, the creativity of the participants presents no problem. What, therefore, seems appropriate is to address those areas of confusion in which notions are being used, by both disciplines in subtly different ways, to unfold the meaning of these complementary viewpoints and to discover those areas in which old and new ideas do not cohere.
In what follows I shall briefly sketch out a number of areas which are of particular interest to me, areas in which particularly difficult questions are posed and in which a new creative approach is needed. It is possible that deeper insights will be gained in these fields, not so much through new ideas, but through a process of clarification and dialogue. The areas I will talk about embrace physics, biology, artificial intelligence and the cognitive sciences and involve questions about order and chaos, language, meaning, mind and information, emergence, novelty and creativity.
https://web.archive.org/web/20040605055331/http://www.fdavidpeat.com:80/bibliography/essays/bermuda.htm
Both his words and manner of speech seemed at first totally unfamiliar to me, and yet somehow they stirred memories - as an actor might be stirred by the forgotten lines of some role he had played far away and long ago.