I first learned about this book from a review by Douglas Hofstadter in his Scientific American column, Metamagical Themas, which ran through most of the mid-eighties. He gave it as an example of a trendy sort of pop philosophy, the basic idea of which was to take certain statements by prominent physicists about what they thought quantum mechanics meant, draw parallels with certain statements made by eastern mystics about their view of reality, and declare, in effect, that "Western science is finally catching up with Eastern thought," as Hofstadter put it. He thought this kind of thing was "superficial and misleading", at least with regard to the view of quantum mechanics it presented (not being an Eastern mystic, he didn't presume to say how they felt about it). I was in college at the time, and I borrowed a copy of Zukav's book to see if Hofstadter's criticisms seemed accurate.
I could simply end the review here by saying that, by and large, the criticisms were accurate, and I came away from the book with much the same view as Hofstadter had. But that was twenty years ago, so why am I writing about it now? Well, for one thing, the mystical view of physics that Zukav presented does not seem to have gone away, as people like Hofstadter and myself perhaps hoped it would back then. For another, Zukav has now written several more books, and although they are not about physics, it is clear from his introductions to all the books (including the one to the new 2001 edition of Wu Li Masters) that he thinks the newer books have some claim to validity because they build on the philosophy about reality that he expounds in this one. It is hard to express this philosophy in a few simple sentences, but Zukav doesn't do a bad job of summing up his view of it, along with his view of its major competitor, early in the book:
The old physics assumes that there is an external world which exists apart from us. It further assumes that we can observe, measure, and speculate about the external world without changing it. According to the old physics, the external world is indifferent to us and to our needs...
According to quantum mechanics there is no such thing as objectivity. We cannot eliminate ourselves from the picture. We are a part of nature, and when we study nature there is no way around the fact that nature is studying itself. Physics has become a branch of psychology, or perhaps the other way round.
Anyone reading the above who is familiar with the history of quantum mechanics, and the philosophical discussions among scientists about it, will recognize several major mischaracterizations. First of all, the proposition that "there is an external world which exists apart from us" is not an assumption of physics, either old or new: it is a conclusion drawn from the evidence, and as such it is equally true of the new physics as of the old. In fact, it is really the same proposition as "we are a part of nature" (I'll discuss this further below), which Zukav lists as a "discovery" of the new physics even though it was perfectly obvious to the old physics as well. And quantum mechanics certainly does not claim that there is no such thing as objectivity. Quantum phenomena, like the energy levels for the hydrogen atom, and the resulting spectral lines that are observed, are perfectly objective; everybody observes the same ones. As for physics becoming a branch of psychology, or psychology becoming a branch of physics, a simple look at the kinds of research going on in the two fields would make it plain that they are not likely to become unified any time soon.
Zukav's last statement about the old physics, that it says "the external world is indifferent to us and to our needs", helps us to see more clearly where Zukav is coming from. He doesn't like this view, that the universe doesn't "care" about us, and he likes quantum mechanics because it seems to him to provide an escape from that view. He is far from being the only one with such a preference; in fact, even many scientists who, unlike Zukav, accept the view that the universe is is indifferent to us admit that they don't necessarily like it. Steven Weinberg, in his famous book on the Big Bang theory, The First Three Minutes (which was published around the same time as the original edition of Zukav's book, by the way), says that "the more the universe seems comprehensible, the more it seems pointless." He goes on to say that he does not take that view of the universe because he wants to, but simply because that is what the evidence says. And Weinberg was not talking about classical physics--the Big Bang theory requires full-blown quantum mechanics and relativity and is as firmly a part of "the new physics" as anything.
The simple view, then, would be that Zukav has simply misunderstood his subject; he has taken a few speculative statements by a few physicists about the meaning of quantum mechanics and stretched them far beyond their limits. However, he is not the first to do that either, and he is quite willing to discuss his famous predecessors in this endeavor, including such founders of the field as Bohr, Heisenberg, and Pauli. His views are also shared, at least to an extent, by some contemporary physicists and philosophers, many of whom are named in the Acknowledgments to the book, and who read over it at Zukav's request--some only parts, but at least four read the entire manuscript and offered extensive comments. But many other contemporary physicists and philosophers who hold quite different views are conspicuous by their absence, and this is a major failing of the book, not because any book on quantum mechanics must scrupulously include all viewpoints, but because Zukav does not pitch this book as expounding his own personal philosophy, but as simply trying to lay out for the lay person what the new physics says. What he ends up laying out, however, is often what he would like the new physics to say, and what he and a few others, including some physicists, believe the new physics says--but which many other physicists, whom Zukav did not bother asking about the matter, do not believe the new physics says, and which is not by any means required by either the phenomena or the basic theory of the new physics.
It is possible that this is not Zukav's fault--that he does believe that the philosophy he expounds is necessitated by the findings of quantum mechanics. It is possible that the physicists he talked to were not as scrupulous as they should have been at distinguishing the established part of the new physics--the experimental results and the basic theory that explains them--from their particular philosophical views on why the basic theory works as well as it does. Certainly some physicists do skimp on such things--but as far as I can see from reading what many physicists have written for lay people about what they do, most of them do quite clearly distinguish the facts from their speculations. If Zukav failed to catch this distinction, then the error has to be at least partly his.
But there may be another, deeper reason for Zukav's basic misunderstanding of quantum mechanics. To get at that, I will quote from the introduction to the book:
Generally speaking, people can be grouped into two categories of intellectual preference. The first group prefers explorations which require a precision of logical processes. These are the people who become interested in the natural sciences and in mathematics. They do not become scientists because of their education, they choose a scientific education because it gratifies their scientific mental set. The second group prefers explorations which involve the intellect in a less logically rigorous manner. These are the people who become interested in the liberal arts. They do not have a liberal arts mentality because of their education, they choose a liberal arts education because it gratifies their liberal arts mental set.
By my comments so far I have certainly placed myself into the first group, whereas Zukav, by his own admission, belongs to the second. The distinction he draws may be useful when trying to understand what he calls the communication problem between the two groups (what C. P. Snow referred to as the problem of the "two cultures"). However, Zukav carries this viewpoint much further:
When most people say "scientist", they mean "technician". A technician is a highly trained person whose job is to apply known techniques and principles. He deals with the known. A scientist is a person who seeks to know the true nature of physical reality. He deals with the unknown.
In short, scientists discover and technicians apply. However, it is no longer evident whether scientists really discover new things or whether they create them. Many people believe that "discovery" is actually an act of creation. If this is so, then the distinction between scientists, poets, painters, and writers is not clear...
The fact is that most "scientists" are technicians. They are not interested in the essentially new. Their field of vision is relatively narrow; their energies are directed toward applying what is already known.
Despite Zukav's later avowals that he does consider "technicians" important, it is clear that he empathizes much more with the liberal arts--which may include what he calls "scientists"--than with the sciences. If this were just an isolated passage, one could discount it, but the attitude it betrays pervades the whole book, and it is a pernicious one. Even the "technicians" of science have to have imagination--it can take just as much, if not more, to work out the implications of a new theory as it does to discover one. Einstein discovered the general theory of relativity, but it was others who discovered solutions to his field equations and figured out how to test them with experiments, and those tests required a high degree of imagination to conceive. And it would come as quite a surprise to all those "technician" scientists to be told that what they were doing was not part of the search for the true nature of reality. Working scientists, particularly those whose primary focus is running actual experiments, as a rule have little use for the relativism implicit in Zukav's talk of "creating" new things instead of discovering them.
But even if we leave out the actual designing and running of experiments and just consider theoretical physics, Zukav's denigration of most real scientists as mere "technicians", unable or unwilling to consider new ideas, is just silly to anyone with even a passing familiarity with the field. Granted, the Internet wasn't around when Zukav first published this book, so the frequency with which imaginative new ideas turn up in physics wasn't as easy to see then; but now a quick check on any of several preprint websites will turn up an astounding variety of papers covering the full spectrum from well established theory to educated speculation to far-out brainstorming. Even in 1979, though, Zukav had the assistance of a number of well-known physicists, yet he shows no sign of being aware of the variety of work going on in the field. His view of most scientists as lacking imagination is only a reflection of his own lack of knowledge. The true difference between the scientist and the liberal artist is not that most scientists lack imagination; it is that, while both have imagination, the scientist's imagination is constrained by the need to conform to the results of real experiments; the artist's imagination is constrained only by the need to conform to the internal logic of his work of art. Scientists have to be willing not only to propose new ideas, but to reject them when they are shown to be untenable, and that will be shown by experimental results regardless of how the scientist feels about the idea. An artist may consider and reject a particular idea for inclusion in his work of art, but he does so simply on the basis of his own perception of the work.
The scientific process of testing ideas and rejecting those that don't match up with experimental results takes place for the most part out of sight of nonscientists, who see only the consensus that gets built up and refined over time, but someone who claims to be writing a book to expound physics to the lay person ought to be willing to go behind the scenes enough to see the full process. Of course Zukav must have heard stories from the physicists he lists in his Acknowledgments about imaginative new ideas they had come up with, which were then soundly rejected by the rest of the physics community; but if he believes that those few physicists are really different from most others, that they somehow represent a small minority who actually come up with new ideas and have to struggle against closed-mindedness, he is very much mistaken. I doubt if there is a reputable working physicist who hasn't had the experience of coming up with a new idea that seems wonderful to them, only to have it unceremoniously trounced by peer review, which is just a shorthand for somebody figuring out that the new idea doesn't work. It is true that the reasons given in such cases are often not based on experiment directly, but on a well-accepted theory; but theories aren't well-accepted (and scientists don't reject papers in peer review based on them) unless they are well-tested by experiment.
The bit about scientific theories being constrained by the results of experiments is what gets lost when Zukav starts waxing poetical about the philosophy of quantum mechanics. To his credit, when discussing how the theories of the new physics were arrived at, he does give due attention to the crucial role played by decisive experiments. However, as soon as he begins talking about philosophy, he seems to forget all that knowledge and just assume that anything goes. The fact is that the philosophical view he expounds is not required by quantum mechanics; it is not a consequence of the experimental knowledge we have of quantum systems, but only of a certain philosophical viewpoint that some people have taken towards the theory itself, and that view is most emphatically not a consensus view. Currently in physics (and this is as true at this writing in 2006 as it was when Zukav's book was originally published in 1979) there is no consensus view on the philosophy of quantum mechanics. There are a number of competing views on the subject; I won't go into detail about them because this isn't an essay on the philosophy of quantum mechanics, but they cover a very wide spectrum. Since they all give exactly the same predictions for the results of all experiments, however, they are scientifically indistinguishable, and no scientist claims that any one is "the" philosophy of quantum mechanics. Perhaps someday a clever person will figure out a way to make the different philosophies make different testable predictions (as John Bell, whom Zukav discusses in the book, figured out how to make the different views of Einstein and Bohr on "local realism" in quantum mechanics make different testable predictions), and then we can do the experiments and see. But until then we just don't know--we can only speculate.
Of course many people are impatient with this, and I would venture to speculate that such impatience is far more common among liberal artists than among scientists (using these terms as defined by Zukav's two groups above). In art it is true that you can define your own reality, at least within the context of your work of art. A poem, a painting, or a novel does not have to conform to any vision but the author's own; we happen to like such a work when the author's vision shares enough with ours to resonate with us, but the author does not create the work in order to conform to our vision. Naturally a person who is used to this aspect of the liberal arts will find it irritating when it turns out that science is not like that. There is that niggling little bit about conforming to "external reality", and when reality has not yet spoken--when we don't yet know how to distinguish various possibilities by experiment--the only consistent position to take is that we don't yet know. How dare reality leave us without an answer to our deep question!
In describing the "communication problem" between the two groups (which I mentioned above), Zukav says that when the idea being communicated finally gets through the haze of apparently complex explanations, it actually turns out to be quite simple. It is rather ironic, then, that the actual ideas about which Zukav and others like him make so much philosophical heavy weather do turn out to be quite simple--so much so that in fact they are platitudes when stated plainly (and also have nothing to do with the difference between the old and the new physics, as I observed above). "We are part of nature"--well, duh! Common sense is enough to tell us that, and science supports it strongly: after all, isn't one of the main points of modern science that we are natural creatures, not supernatural beings somehow plopped into natural bodies? But we are only part of nature, not all of it, so there is much of "nature" that is not us, which was there before we were born and will be there after we die--in other words, "there is an external world which exists apart from us". The new physics says that we, like the rest of nature, are made of quantum stuff, not classical stuff; but that doesn't change in the least the relationship between the stuff that is us and the rest of the stuff in the universe. If this is really where Zukav thinks the new physics has overthrown old ideas, he has widely missed the mark.
That is not to say that a lay person can get no value from reading this book. There are discussions of the parts of quantum mechanics that really are philosophically challenging--for example, Bell's discoveries about nonlocality, which Zukav talks about towards the end of the book. It is interesting that here, as almost nowhere else in the book, Zukav actually does talk about various different philosophical positions that can be taken about the results of experiments based on Bell's discoveries. But it is also here that, after canvassing the philosophical positions, Zukav goes into a discussion of Eastern mysticism and its supposed connections with quantum physics. He quotes the physicist David Bohm here to illustrate his claim about how the worldview of physics and Eastern mysticism might converge, but though he acknowledges that Bohm's views are not widely accepted among physicists, he fails to mention that Bohm studied Eastern mysticism, which is why the language he used, as illustrated in the quotes, sounds like that of Eastern mystics. It is perfectly possible--as the works of many other physicists can attest--to discuss the same phenomena without using such mystical language, so the language is more an artifact of the person using it than a reflection of the reality being described. (For more discussion of the actual scientific content of nonlocality, see the last note in the Postscript below.)
The bottom line is that if you are reading just to learn about physics, not to learn about Zukav's particular philosophy about physics, I would not advise relying on this book as a source of information. You will find out things about physics, though there are some elementary misunderstandings and some significant omissions (see the Postscript for a few of the biggest ones I spotted); it is clear, as I mentioned above, that Zukav only talked to a rather narrow group of physicists, and so he missed things that would have become evident had he been more thorough in seeking out viewpoints. But you will also be presented with a philosophy about the physics which is not the only possible one, and is certainly not necessitated by the physics, but which is presented as though it were just as well established as the physics; and you won't be able to tell which is which without information from other sources, because Zukav does not distinguish the two. I believe that that is not the best way to present the basics of physics, but then, as I confessed earlier, I am one of those people who like precise logical processes. It's not that I like only precise logical processes; I have already said that scientists need imagination just as much as artists, and I am quite ready to admit that there are things in life, like love, that do not benefit much from logical analysis. But this book is not supposed to be about art, or love, but about science, and in science we give logical analysis an important role for the very good reason that without it we can't tell good theories from bad. I see no reason not to apply the same logical analysis to philosophies, and if that makes me a "technician", then so be it.
Here are some notes on particular scientific misunderstandings or omissions that I spotted in the book. I will refrain from commenting on Zukav's personal philosophy and on the "paranormal" suggestions that he thinks he sees in quantum mechanics, since the object of this review is not to disparage his philosophy as such, but only to make the point that that philosophy has little or nothing to do with the new findings of modern physics. So I'll just comment on the straightforward science.
(1) Zukav's discussion of the collapse of the wave function incorrectly states that the wave function collapses "from a reality with a theoretically infinite number of dimensions into a reality which has only three". In a footnote a little later on he states that "the state of a system containing n particles is represented at each time by a wave function in a 3n dimensional space. If we make an observation on each of the n particles the wave function is reduced to a special form--to a produce of n wave functions each of which is in a three-dimensional space". From this and other statements in his discussion of wave functions it appears that Zukav doesn't recognize the distinction between the dimension of the space the wave function lives in, and the number of degrees of freedom available to the system; they are not always the same, and it would be more correct to say that a system containing n particles moving in three-dimensional space has 3n degrees of freedom (provided the particles have no spin). But the more important point is that, whether you think of the dimension of the wave function space or the number of degrees of freedom, it doesn't change when the wave function collapses. A collapsed wave function may have a special mathematical form, but its specialness has nothing to do with reducing the dimension of the space it lives in or the number of degrees of freedom of the system.
A brief note on the mathematics of wave functions will help to clarify the problem with Zukav's exposition. Wave functions do not exist in the ordinary three-dimensional space that we perceive; they exist in an abstract mathematical space called Hilbert space. For some systems, such as a single quantum particle moving in three-dimensional space, the full definition of the Hilbert space can be ignored for some purposes, and the wave function can be thought of as a function that assigns a single number to each point in three-dimensional space--but even then the number is a complex number, which is sort of a "two-dimensional" number all by itself, so saying that the wave function is in three-dimensional space is at best misleading. Even in this simple case, however, the Hilbert space is not three-dimensional; it is, in fact, infinite-dimensional (because it has to have one dimension for each possible position the particle can have, and there are an infinite number of them). This fact may be why Zukav states that the wave function before collapse lives in a "theoretically infinite number of dimensions", but as was noted above, this is true after the collapse as well. (Also, there are many quantum systems that have finite-dimensional Hilbert spaces.) By itself this is not necessarily a fatal error; after all, these abstract spaces can't be visualized directly anyway, so we have to have some sort of crutch to make mental pictures of what we think might be going on. But the view of wave functions living in actual three-dimensional space at least some of the time plays a key role in Zukav's philosophy, so the fact that the view is in error is not insignificant when judging the claims he makes.
The fact that a wave function that has just collapsed (because of a measurement made on a quantum system) can have a special mathematical form is also somewhat misleading as Zukav uses it here. Zukav does not seem to understand the fact that any wave function in Hilbert space can be described using more than one "basis". The "basis" of the Hilbert space is more or less analogous to the coordinate axes in ordinary three-dimensional space; we know from ordinary vector analysis that we can describe the same three-dimensional space using different coordinate axes that are rotated or translated relative to each other, without changing any physical predictions (the individual coordinates we assign to events will be different, but the actual physical content of our theories will not change). Quantum mechanics says that the same is true of Hilbert space: we can express the same wave function in more than one basis, without changing the physical predictions of the theory about the results of experiments. The reason this is important is that, in general, a wave function that has the special property Zukav talks about (of being a product of individual wave functions for each component of the system) only has that property in a particular basis; if we change to a different basis the property will no longer hold. For example, if we measure the position of a particle, the resulting collapsed wave function does have a special form in the position basis (it has a nonzero value only for one position, the one we measured the particle to be at), but it does not have that special form in a different basis called the momentum basis (where the wave function is expressed as assigning a probability amplitude to each possible momentum for the particle instead of each possible position). So the fact that collapsed wave functions can look "special" is really only an artifact of the particular basis we choose to look at them in.
(2) In his discussion of the principle of relativity, Zukav makes this curious statement:
Unfortunately, there is one catch in all this. No one yet has found a co-ordinate system in which the laws of mechanics are valid!
As a plain statement about whether suitable inertial reference frames (frames in which the principle of inertia holds--bodies not acted upon by any external forces remain either at rest or in motion in a straight line at a constant speed) are known, this is simply false. Spacecraft en route between planets or other astronomical bodies provide just such frames of reference, and this had been experimentally verified in 1979. (Among other things, it was verified by the experience of the Apollo astronauts on their way to and from the Moon.) Even a spacecraft in orbit about the Earth is a fairly good approximation of such a frame--better than a laboratory at rest on Earth's surface, which, as Zukav observes, exhibit non-inertial effects due to the Earth's rotation (the obvious non-inertial effect of the Earth's gravity can be ignored if only horizontal motion is considered). Orbiting spacecraft still see (small) tidal effects due to the Earth's gravity, which is why a spacecraft not in orbit is a better choice for a truly inertial frame.
It is true that there were not yet any spacecraft in the late 19th and early 20th century, when these issues were being debated in physics, but Newtonian physics predicted quite clearly what would be observed in one, and those predictions were correct as far as the inertial nature of the reference frame. The deviations from the exact Newtonian predictions due to special and general relativity do not affect the inertial nature of the reference frame of any given spacecraft; they only affect the relationship between its coordinates and those of other inertial frames, such as other spacecraft. Everyone understood quite clearly that the non-inertial nature of the Earth as a reference frame was due to its rotation and its gravity, and those effects could be, and were, corrected for in order to verify Newton's laws of motion. So Zukav's apparent belief that without a "perfect" inertial frame of reference, the laws of mechanics cannot be verified, is also false.
A little later on, Zukav says:
This problem [of not having found a truly inertial coordinate system] is related to relativity, which is the problem of determining absolute nonmotion, in an intimate way. If such a thing as absolute nonmotion were detected, then a co-ordinate system attached to it would be the long-lost inertial frame of reference, the co-ordinate system in which the classical laws of mechanics are perfectly valid.
This is also false; in fact, it is by no means logically guaranteed that a co-ordinate system that was found to be in absolute non-motion would be an inertial frame of reference. The only theories that made this claim were ether theories, and Zukav's discussion later in the same chapter makes it clear that ether theories were ruled out by experiment. Furthermore, it is contradictory as a statement about the principle of relativity (Galilean or otherwise); the principle of relativity is all about working with inertial frames of reference without having to discover one that is in absolute nonmotion. Discovering such a frame would amount to falsifying the principle of relativity.
Zukav seems to clearly recognize all this earlier in the same chapter, and it's not clear why he suddenly turns around and contradicts it here. It is possible that he is trying to make a philosophical point: that somehow, the laws of mechanics--whether Newton's, Einstein's, or anybody else's--are not really "verified" unless a reference frame can be found that is inertially "pure", free of all forces, so that we can check that yes, in such a frame, the principle of inertia holds exactly. But that's false too; another key point of the theory of relativity is that the idea of a global inertial reference frame--a single inertial frame that can cover the entire universe--is an idealization; in the real universe, there are only local inertial frames. The immediate vicinity of a freely falling body, such as a spacecraft in transit between, say, the Earth and the Moon, is such a local inertial frame, because locally--within the spaceship--the principle of inertia holds: put a small object like a pen at rest in front of you and it hangs there, remaining at rest, until you apply a force to it. To verify the "laws of mechanics", such local inertial frames are good enough.
(3) Zukav talks about spacetime diagrams and how useful they are in relativity, but it's not clear that he really understands how to use them. If he did, he wouldn't have said, after his discussion of Penrose-Terrell rotation (which is not bad, but for a better and more current discussion with more details, see the Usenet Physics FAQ entry here), that "as yet, no analogous explanations have been found for the time dilation that accompanies moving clocks or the increase of mass that accompanies moving objects, but the effort, relatively speaking, is young". Actually, spacetime diagrams can fully explain length contraction and time dilation, including both what an observer in a stationary frame actually sees of an object in a moving frame, and what space and time coordinates the stationary observer assigns to events in the moving frame. Also, there are energy-momentum space counterparts to spacetime diagrams (where the "space" dimensions are the momenta in each direction and the "time" dimension is energy) which make quite clear the relationship between rest mass and the full relativistic energy and momentum of a moving object. (By the way, I'm also confused by the statement that "the effort...is young." Spacetime diagrams have been around almost as long as relativity itself--Minkowski first introduced them in 1908, three years after Einstein published his special relativity paper, and they have been basic tools in relativity physics ever since.)
In fact, Zukav doesn't even fully understand Terrell's explanation of length contraction (and the apparent rotation that goes with it), because if he did, he would realize that the diagrams he draws to illustrate the rotation aren't labeled with any time coordinates, and when you do so label them, you find that time dilation pops out as well as length contraction. This is really just another way of understanding what spacetime diagrams tell you about the situation: that both the space and the time coordinates of a moving object are "projections". One of the great virtues of spacetime diagrams is that this becomes visually obvious.
(4) Zukav's sketch of the history of the study of black holes is, to say the least, garbled. Finkelstein's 1958 paper was indeed important in the field, but it could hardly be said to have been the first to "theorize" about black holes (that name, incidentally, was coined by Wheeler in the late 1960's). The Schwarzschild solution to the Einstein field equation was discovered in 1916, and the presence in it of what we now call the "event horizon", from which nothing that once passes inside can escape, was known in the 1920's. Eddington discussed it in several papers and in his popular work on physics from that time. Oppenheimer and Snyder's 1939 paper was key because it was the first calculation of how what we now call a black hole could form from the gravitational collapse of a sufficiently massive star. However, all these studies did labor under a conceptual block imposed by the particular coordinate system that Schwarzschild used to describe his solution to Einstein's equation; what Finkelstein's 1958 paper did was to introduce a new coordinate system (dimly previsioned by Eddington) that made it much easier to visualize the spacetime structure of the solution, lifting the conceptual block and enabling the flowering of black hole studies in the 1960's and 1970's. Kip Thorne's Black Holes and Time Warps gives a good, fairly detailed treatment of this history and puts the Finkelstein paper in its proper perspective. Thorne's book was written in 1993, well after Zukav's original publication of this book, but the historical events leading up to the "golden age" of black hole studies in the 1960's and 1970's were well known when Zukav first published (not to mention that he could have done some checking up for the new 2001 edition).
(5) Zukav's view of the state of particle physics current when the book was published (in 1979) is not a good reflection of what was then the general consensus. (It is an even worse reflection of the consensus in 2001, when the new edition was published, but we'll get to that.) First, it portrays as questionable or speculative theories that may have been so in the 1960's and early 1970's, but which were well established by 1979. He compares the present state of particle physics to Ptolemaic theory, calling the accumulation of theoretical devices "analogous to the addition of epicycles piled on an already unwieldy theoretical structure." It is true that a fair number of physicists held that opinion when the underlying structure of "the particle zoo" had not yet been worked out and tested experimentally, but that process--the development of quark theory and quantum chromodynamics and the development of electroweak theory--was well-nigh complete in 1979, and Zukav seems to be either unaware of or unwilling to credit this consensus. He barely mentions quark theory at all, and electroweak theory only in a brief footnote, where he says that "recent evidence gives growing credence" to that theory, a considerable understatement in 1979 given that it was the very year Weinberg, Salam, and Glashow received the Nobel Prize for it, the experiments which decisively confirmed the theory having been completed in 1978.
It is true that there were still contrarians among physicists concerning these theories in 1979, and some of them are listed in Zukav's Acknowledgments, so his sentiments about epicycles may come from talking to them; but here again, he is presenting, not the basic physics, but his own personal philosophy about the physics--or perhaps his personal opinion about how the consensus ought to have worked out. In any case, his discussion is certainly very much out of date as to progress in the field. He talks about S-matrix theory, which was known to have failed a number of tests by the 1970's, as though it were still viable, and the main reference work he cites on particle physics dates from 1965. (It is true that S-matrix theory can still be of value as an approximation in some contexts, but Zukav never talks about that kind of theoretical work at all, perhaps because he considers it merely "technician" work--he is solely concerned with theories that are supposed to tell us about the fundamental nature of reality.) In such a fast-changing field, using information that much out of date, without any disclaimers, is certainly misleading, particularly when it gives a highly inaccurate view of the state of knowledge. And even if this might have been marginally excusable in 1979, there is no excuse for it in a new edition published in 2001, when the intervening years have vastly increased the experimental constraints on theories, so that now there is no dispute whatever that, at the energies accessible to our current experiments, the Standard Model of particle physics (which is quark theory combined with electroweak theory) is the correct theory.
(6) Zukav talks about quantum logic as though it somehow magically transcends mathematics, which he seems to think requires classical logic to function at all. He says:
A mathematical analysis of subatomic phenomena is no better qualitatively than any other symbolic analysis, because symbols do not follow the same rules as experience. They follow rules of their own. [emphasis in original]
Actually, quantum logic was precisely an effort to construct a symbol system that would "follow the same rules as experience", or at least the experience of doing experiments in quantum mechanics, and it more or less succeeded in doing that. It is quite true that classical logic is not a good system of rules for symbol manipulation if you are trying to understand quantum behavior; but contrary to what Zukav appears to believe, mathematics is not restricted to any one set of rules for manipulating symbols. Rather, mathematics is an ongoing effort to expand the capabilities of our symbol systems by finding ones that follow new and different rules, so that we can have more options when we are trying to pick a symbol system whose rules accurately reflect the structure of whatever we are trying to understand. Classical logic is a well-known symbol system precisely because its rules are good rules for understanding classical systems--i.e., the ones we encounter in our everyday lives, the ones which were common in the environment in which we and our minds evolved. But that doesn't mean that we have to either use classical logic or stop doing mathematics and start doing something else. Mathematics is not a single monolithic entity where everything has to play by the same set of rules; it is just a toolbox of useful abstract systems that mathematicians are expanding in an ongoing effort. Quantum logic is just one more tool in the toolbox.
(It does seem a little outlandish to claim that Zukav thinks quantum logic isn't mathematics, but I can't find any other way to make sense of what he says. He says that "symbols do not follow the same rules as experience", but he says that quantum logic does, so either he's contradicting himself, or he doesn't believe that quantum logic uses symbols. Since he calls mathematics a language, and says that a language "is constructed of symbols", then it would seem to follow that he doesn't believe quantum logic is mathematics. But of course it is, and of course it does use symbols. John Von Neumann, who first discovered quantum logic, was a mathematician, and Zukav says so early in his discussion of quantum logic, so Zukav would seem to also believe that Von Neumann was working outside his field, which would have come as a big surprise to him and everyone else since his book was titled The Mathematical Foundations of Quantum Mechanics--Zukav also mentions this title in his discussion. It is all very confusing to a simple man like me who applies classical logic in those situations where it is warranted.)
(I can't help mentioning also, thought it isn't strictly germane to a review of Zukav's book, that I personally have never understood why quantum logic was thought to be such a breakthrough. It isn't as though physicists sat around working with syllogisms in classical logic to predict the behavior of quantum systems. They used the full mathematical formalism of wave functions, state vectors, Hilbert spaces, and operators, and they still did so after quantum logic was discovered. Zukav's apparent belief that quantum logic replacing classical logic is the right way to make progress in quantum physics seems to me to be rather like a belief that giving a heavier screwdriver to a person with a screwdriver is the right way to make progress in driving in nails.)
(7) The philosophical implications of nonlocality in quantum mechanics have been a contentious issue ever since it was first shown theoretically to be an unavoidable consequence of quantum mechanics by John Bell in 1964. At the time of first publication of this book (1979), experiments had been done (the main one being the Clauser experiment which Zukav mentions) that were consistent with the predictions of quantum mechanics, but still left some "loopholes" for theorists who were unwilling to accept the full implications. The Aspect experiments in 1982 (which Zukav also mentions in the 2001 edition of the book--it is interesting that here he has taken pains to update the content of the book from the original edition, which as I have noted, he does almost nowhere else) were intended to definitively close the loopholes, and it was initially thought that they had; but theoretical work done in the 1990's has uncovered other possible ways out of the nonlocality conclusion that were not definitively ruled out by the Aspect experiments. So technically it is still an open question whether nonlocality, as manifested in violations of the Bell inequalities, is truly confirmed by experiment, but no physicists in the field seriously expect it not to be confirmed when sufficiently accurate experiments can be done.
As I noted in the review above, Zukav devotes considerable space to discussing the various philosophical positions which were known in 1979 regarding the Bell inequalities and nonlocality. For the most part this discussion captures the positions, and the implications of the various experiments that have been done or could be done, reasonably well. However, once again, as soon as he goes over into philosophy, he goes far beyond what is really implied by the theory that he is talking about. Granted, he is quoting Bohm, but he clearly believes that Bohm was stating, not his own personal philosophical position, but an unavoidable implication of the physics of his theory. The theory under discussion is Bohm's "pilot wave" model of how nonlocality might work, which is not a generally accepted theory, it is true; but the point I am making here is that what Zukav quotes Bohm as saying is not part of the physics even of Bohm's own theory--it is just Bohm's personal opinion, even though it is part of a physics lecture.
Here is what Zukav quotes from Bohm:
The word "reality" is derived from the roots "thing" (res) and "think" (revi). "Reality" means "everything you can think about". This is not "that-which-is". No idea can capture "truth" in the sense of that-which-is.
The ultimate perception does not originate in the brain or any material structure, although a material structure is necessary to manifest it. The subtle mechanism of knowing the truth does not originate in the brain.
There is a similarity between thought and matter. All matter, including ourselves, is determined by "information". "Information" is what determines space and time.
(By the way, revi is not the Latin word for "think", and I'm not sure where Bohm picked up his putative etymology for the word "reality". According to my sources, it does derive from res, meaning "thing", but that's the only root word--the word "real" comes from the same source and was probably the earlier derived word, with "reality" having the adjectival ending "-ity" tacked on later. So "reality" is just "whatever quality it is that real things have." But that's Bohm's error, not Zukav's--I just wanted to show off my five years of Latin in high school :-).)
Etymology aside, Bohm's physical theory about nonlocality has nothing to do with the appearance-reality distinction in philosophy (the question of whether we can directly perceive or think about "that-which-is"); it has nothing to do with how perception or thinking or knowing works in the brain; and it has nothing to do with any scientific concept of "information" such as is studied by information theory. (It may be that Bohm was using the term "information" in some other sense than the standard scientific one which is dealt with by information theory--but it certainly was not a scientific sense of the term, and Zukav does not discuss what he thinks it means. Throwing around vague terms, or terms that can have several significantly different meanings, without defining them precisely may be a common practice in certain types of philosophy, but it isn't science.)
All the pilot wave theory says is that the fundamental units of physics are particles, which act just like "real" classical particles in that they have definite positions and velocities at all times and move along definite trajectories, and "pilot waves", which flow along with the particles and guide their trajectories in order to keep the results of experiments consistent with quantum statistics. The only counterintuitive part of the theory is that the pilot wave has to update itself nonlocally (meaning that the physical rule for how it evolves in time takes into account the values of physical parameters at spacelike separated locations--Zukav defines the term "spacelike separated" when he talks about relativity), so it looks as though the wave is updating itself faster than light (although, since the theory is consistent with quantum mechanics, no actual signal can be transmitted faster than light). But all of this is perfectly objective and conceptually easy to understand--in fact, if anything, Bohm's theory is more like classical physics (the "old" physics) than standard quantum mechanics! The fact that Bohm read all of these deep philosophical implications into his theory does not mean they were really there.
I said I wouldn't discuss Zukav's philosophy per se, but I can't let this quote go by without comment:
It is ironic that while Bohm's theories are received with some skepticism by most professional physicists, they would find an immediately sympathetic reception among the thousands of people in our culture who have turned their backs on science in their own quest for the ultimate nature of reality.
I talked above about Bohm's pilot wave model and what parts of his views may or may not have been received with skepticism; here I want to talk about all those people who would give his views a sympathetic reception because they've turned their backs on science. To put it bluntly, so what? How does that make Bohm's views any more (or less) correct than they would otherwise be? Nonscientists who are not familiar with the relevant theories and experiments don't have a right to an opinion about any particular piece of science; still less people who have intentionally turned their backs on science.
The real irony here is that Zukav and all those people who have turned their backs on science are the ones who are guilty of the sins with which Zukav charges scientists. Zukav seems to believe that most scientists don't really think for themselves, but just accept what is said by those in authority; yet he quotes the philosophical views of famous physicists with approval, not because he understands the physics well enough to form an opinion, but simply because they're famous physicists--whereas scientists today are quite ready to say that Einstein, Bohr, Heisenberg, or any other famous figures were just plain wrong about some things, if that's what they think. Zukav claims that most scientists lack imagination; yet Zukav's idea of being imaginative is to view the world through a philosophy that is thousands of years old--whereas modern science's idea of being imaginative is to come up with something that nobody has ever thought of before. Armchair philosophers throughout history have come up with ideas like "we are part of nature", but nobody before Newton came up with the inverse square law of gravity, nobody before Einstein came up with the curved spacetime picture of general relativity, nobody before Heisenberg came up with the uncertainty principle. Instead of continually rehashing old ideas that have no resolution, science keeps on adding new ideas to the fund of human knowledge. And the best that Zukav can do is to say that, well, these so-called new ideas must really be the old ideas after all. Well, they aren't.