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The physical basis of the direction of time. 2. ed. (English) Zbl 0770.00002

Berlin: Springer-Verlag. x, 188 p. (1992).
The idea of this book is the result of some lectures the author gave at the University of Heidelberg during the summer terms of 1979, 1982, 1986.
By comparison to the first edition (Springer-Verlag, 1989) (see also Zbl 0535.00033), this second edition is enriched with the results of the most recent developments and researchers in the field; this fact is reflected by the numerous additions (especially at Chapter 6.5, and Section 4.2), and by the supplementary comments. The book refers to one of the most fascinating major problems of modern physics: the asymmetry of natural phenomena under time reversal (a striking fact, maybe too obvious to us, because it affects our whole life!). There are investigated the most important classes of physical phenomena that might contribute to the characterization of the “time-directedness” of the world (that has often been considered “more fundamental” than the laws of nature themselves — Eddington 1928, Einstein 1949). The author tries to determine the interrelations between these classes of phenomena — in order, to discover the (cosmological) common root, the “ultimate cause” of this asymmetry.
The approached subject imposes an overview of various areas of physics (from thermodynamics, quantum measurement theory to general relativity and cosmology). That is why the author’s intention was not to describe the “technical details” of each field, but to emphasize the physical ideas of the various fields, as well as their interconnectedness.
This position of the author did not at all involve a lack of rigour. It determined the concision, the great clarity of the book, as well as a rigorous selection of the elements that are relevant for the tackled subject.
Consequently the book does not address mainly the specialist of a strict domain; it is intended for those that are interested in the (so fascinating) connections between top fields of physics. It can also be welcome for philosophers who are interested in aspects of theoretical physics.
In the Introduction it is discussed the place occupied by the considered subject in the scenery of modern physics; there are outlined the guiding lines of the book, as well as the new points of view of the author concerning some very controversed subjects. There are also specified the meanings of some terms that are used throughout the book (in order to avoid any language confusions).
Each of the following chapters is dedicated to the most important classes of phenomena characterizing a direction in time.
Chapter 1 (“The Physical Concept of Time”) is concerned with a review of the evolution of the concept of time in physics (from Aristotle to our days). There is also discussed the author’s understanding of the concept.
The second Chapter (“The Time Arrow of Radiation”) contains things that are (almost) generally accepted. In all radiation phenomena one finds the retarded solutions (a wave appears after its source event). The phenomenon of radiation emission is not the “temporal inverse” of the radiation absorption; this because we can have spontaneous emission (in the absence of the incoming radiation), but we can’t have absorption without outgoing radiation. It is also shown that in order to characterize absorbers the Wheeler-Feynman condition has to be supplemented by an asymmetric condition.
The third Chapter is dedicated to the thermodynamic arrow of time — the most important one in our everyday life. The second principle of thermodynamics characterizes a direction in time. It cannot be explained by means of statistical arguments, and it appears like a supplementary restriction (besides the dynamical laws) to the possible processes. It is emphasized the fundamental observer-relatedness of the macroscopic description (although this might seem to be in conflict with the objective nature of thermodynamics!). There is also discussed the spontaneous formation of ordered structures.
Chapter 4 (“The Quantum Mechanical Arrow of Time”) contains an attempt to place the quantum mechanical measurement process in its correct relation to other irreversible phenomena. Its irreversibility is connected with the indeterminism corresponding to the probabilistic interpretation. It is the chapter that might give birth to polemics — due to the fact that it avoids the (non)concepts of the Copenhaga school (dualism, complementarity).
In Chapter 5 (“The Time Arrow of Spacetime Structure and Cosmology”) there are described the cosmological aspects of arrows of time. On the basis of general relativity and quantum field theory there are studied some properties (including thermodynamic ones) of the systems with gravity. It is justified the idea that the expansion of the whole universe might be the “Master Time Arrow” — from which all others may be derived.
The sixth Chapter (“The Quantization of Time”) is dedicated to the attempts to understand the problem of the quantization of the spacetime metric, and consequently of time itself. It is a very topical, active problem.
Next there is an Epilogue.
The book contains an impressive (we’d say exhaustive) list of references: almost 300 titles (papers and books). At the end of each section there are given the suitable references. There are also emphasized the fundamental problems left unsolved. We have to mention the high scientific value of the book, its rigorous, well-documented discussion of the subject, the refinement and subtlety of its reasonings. We strongly recommend it to students and specialists in various fields of theoretical physics.
Reviewer: I.Bena (Iaşi)

MSC:

00A79 Physics
80A05 Foundations of thermodynamics and heat transfer
83F05 Relativistic cosmology
81P05 General and philosophical questions in quantum theory

Citations:

Zbl 0535.00033
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