Book review of David Bohm

David Bohm:
THE UNDIVIDED UNIVERSE (Routledge, 1993)

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One of Quantum Theory's most direct consequences is indeterminism: one cannot know at the same time the value of both the position and the momentum of a particle. One only knows a probability for each of the possible values, and the whole set of probabilities constitute the "wave" associated with the particle. Only when one does observe the particle, does one particular value occur, only then does the wave of probabilities "collapse" to one specific value.
Bohm reviews other interpretations of this phenomenon and focuses on the mystery of the collapse of the wave function, the transition from the quantum world to the classical world. This introduces a discontinuity that has puzzled physicists ever since. Bohm believes there is a deeper level at which the apparent discontinuity of the collapse disappears.
Bohm offers instead an interpretation in terms of particles with well-defined position and momentum. What he adds to other interpretations is "hidden variables", in the form of a quantum potential. A particle is always accompanied by such a field. This field represents the subquantum reality.
Bohm introduces the notion of "active in-formation" (as in "give form", for example to a particle's movement). A particle is moved by whatever energy it has but its movement is guided by "information" in the quantum field. The quantum potential reflects whatever is going on in the environment, including the measuring apparatus. Note that the effect of the quantum potential depends only on its form, not on its magnitude.
Since this quantum field is affected by all particles, nonlocality is a feature of reality: a particle can depend strongly on distant features of the environment. And, viceversa, the whole cannot be reduced to its parts.
The earlier interpretations of Quantum Theory were trying to reconcile the traditional, classical concept of "measurement" (somebody who watches a particle through a microscope) with a quantum concept of "system". Bohm dispenses with the classical notion of "measurement": one cannot separate the measuring instrument from the measured quantity, as they interact all the time. It is misleading to call this act "measurement". It is an interaction, just like any other interaction, and, as Heisenberg's principle states, the consequence of this interaction is not a measurement at all.
This book offers a more technical treatment of implicate order and its relationship to consciousness than Wholeness and the Implicate order .

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