The Comprehensible Cosmos: Where Do the Laws of Physics Come From? [Hardcover]

Review of Victor Stenger's Comprehensible Cosmos

January 24, 2007

Where do the laws of physics come from? The Power of P.O.V.I.

In this admirable new book, physics professor Victor Stenger once again exhibits his notable ability to convey complex ideas of physics with simplicity and elegance, while not sacrificing mathematical rigor and detail. Moreover, the book offers a "big-picture" perspective that will appeal to both physicists and non-physicists. However, although not required, a basic familiarity with physics and a mathematical background will greatly enhance readers' appreciation and comprehension of the book, particularly concerning the helpful mathematical supplements provided at the end.

Here Stenger takes on "ultimate" questions, such as, Where do the laws of physics come from? and Why is there something rather than nothing?- answers to which are commonly believed to be found exclusively within the province of theological and philosophical discourse and to be inherently beyond the reach of empirical and theoretical science. Stenger argues that the extraordinary empirical success of our current models of physics, though still incomplete and provisional, gives us good grounds to assume that they are on the right track: the cosmos is indeed comprehensible, and our current physical models provide a description of nature that is likely to faithfully reflect aspects of a reality that exists independently of our thoughts and particular physical models.

Stenger argues that, contrary to some popular views, the so-called "laws of physics", such as the great conservations laws, are not restrictions on the behavior of matter imposed by an external agent or by a world of abstract Platonic mathematical forms. Rather they arise from the self-imposed requirement that physicists' descriptions of nature be independent of the particular point-of-view of observers- that they be point-of-view invariant. In order to ensure universal applicability and to describe reality as objectively as possible, physicists aim to construct mathematical models that describe nature in such a way that these descriptions do not depend on the particular point of view or reference frame of observers. For instance, the law of conservation of energy is a manifestation of time-translation invariance. A description of nature that does not depend upon the absolute time at which observations are made will automatically entail the conservation of a quantity called `energy'. Similarly, the law of conservation of momentum naturally arises from the requirement that physicists' descriptions of nature are space-translation invariant- that they do not depend upon any particular point in space.

Stenger's account builds upon the work of mathematician Emmy Noether, who proved that certain mathematical quantities called the generators of continuous space-time transformations are conserved when those transformations leave the system unchanged. Hence, the great conservation laws are consequences of point-of-view invariance and thus are reflections of the symmetries of space and time. As Stenger puts it: "If you wish to build a model using space and time as a framework, and you formulate that model so as to be space-time symmetric, then that model will automatically contain what are usually regarded as the three most important "laws" of physics, the three conservation principles". Stenger further demonstrates how Newtonian mechanics, quantum mechanics, and special and general relativity also arise naturally from the point-of-view invariance and symmetries of our physical models.

In addition to showing the intimate connection between the laws of physics and the symmetries of space and time, Stenger argues that features of our complex lower energy universe may be accounted for by the spontaneous breaking of symmetries that were present during the higher energy state of the big bang. Our universe is akin to a less symmetric snowflake that froze out of a more symmetric sphere of water vapor. Stenger discusses the possibility that our universe arose via a well-understood process of quantum tunneling from a highly symmetric void, empty of energy, particles, space, and time- a featureless state essentially equivalent to `nothing' . Since the void also exhibits space-time symmetries, the laws of physics are ultimately derived from the symmetries of the void. Indeed, Stenger argues that the laws of physics are not really laws at all, in the usual sense of the term. On the contrary, they are reflections of the absence of laws- they are what Stenger refers to as "lawless laws". Other aspects of nature, such as the apparent indeterminism of quantum mechanics can be accounted for by an element of randomness in the universe (which, Stenger notes, is itself a manifestation of invariance). Ultimately then, symmetry and randomness lie at the bedrock of reality. Hence, the universe is not only comprehensible, but may have arisen in the simplest way possible: randomly and spontaneously from a highly symmetric void, that is, from a state essentially indistinguishable from `nothing'. But then why is there something rather than nothing? Indeed, if the universe came from a void, then why did it not remain as a void? The answer Stenger offers, and which gains support from the work of other physicists, is that a symmetric void is unstable- hence there had to be something. Our universe is simply a different phase of `nothing', just as ice and steam are different phases of water.

There are plenty more topics discussed in this original and insightful book, including particle physics, cosmology, and thermodynamics, which are beyond the scope of this review. Perhaps some readers might complain that Stenger is too cautious in his lack of commitment to particular physical models of reality. At times he suggests that "scientific criteria cannot distinguish between viable metaphysical schemes" and that space and time are useful inventions that cannot be proven to exist. While this may be the case, this suggestion may be seen to weaken his thesis that the cosmos is comprehensible and that physics is not just another cultural narrative. On the other hand, Stenger emphasizes throughout that our physical models ultimately must be constrained by and consistent with empirical observations. Indeed, the relentless testing of the observational consequences of our physical models is what distinguishes physics from fiction. Thus, our physical models, while human inventions, are not just arbitrary cultural constructs. To the extent that they succeed in describing nature and surviving risky empirical tests, they likely represent aspects of an underlying reality independent of our specific models. Moreover, Stenger comments on how a particulate model of reality characterized by "atoms and void", which he explicitly favors, displays some virtues over a model characterized by waves, fields, and other "Platonic" mathematical constructs. If indeed physics does have implications for metaphysics, then physics might someday provide compelling empirical or theoretical reasons to prefer one hitherto observationally equivalent metaphysical model over another. In any case, readers will appreciate the elegance and simplicity of Stenger's expository style, which are paralleled by the elegant simplicity of the scenario he has described for the origin of the universe and of the laws of physics.

Yonatan Fishman, PhD

Department of Neurology

Albert Einstein College of Medicine

This small (320 pages of text) is, in essence, an epitome of the basic physics of our day. It covers space and time, classical and quantum mechanics in their fundamental form, relativity, thermodynamics, cosmology, particle physics and their interactions. Each topic is treated in rough terms in a main chapter and with precision in a mathematical appendix. What makes this work unique (and not just another textbook of physics) is an attempt to systematize the material under a few very basic principles. Most important of these is the generalized form of invariance called "point of view invariance" by the author, though other postulates are introduced as necessary. My only quibbles are: (a) these principles could be summarized somewhere, (b) the debates discussed in the book over instrumentalism, realism, etc. are too perfunctorally discussed. However as this is not a philosophy of science book on those topics, the oversights can be forgiven. Finally, (c) as a non physicist, I do find myself wondering which approximations are good ones and which not. Sometimes, to achieve equality of two terms, etc. Stenger makes mathematical approximations. This is indispensible; instead what could have been useful is some discussion of where the assumptions so made break down. This is done in some places (e.g. in the discussion of the connection between Newtonian and Einsteinian understandings of motion) but not others, so the flaw, such as it is, is not ubquitous.

Other merits of the book include a clear writing style, bibliographic suggestions for further reading, helpful diagrams and some historical perspective by including years of death for various key physicists.

This is the third book from Professor Stenger that I've read. In my mind, he's certainly the "Richard Dawkins" of general-audience physics books.

I won't repeat too much of the content of other reviewers of this book, but rather just touch on a couple areas that I found particularly interesting:

I enjoyed how the professor stresses the simplicity of nature. For example, he shows in this book how almost all of physics comes from generalized gauge invariance, which he calls "point-of-view invariance." By the end of the book, we're shown how the "laws" of physics are not really laws at all. In the professor's well-expressed view, our traditional physical laws, in fact, are not somehow built into the fabric of the universe or handed down from above, but rather emerge from natural symmetries of a void.

On a related note, I also enjoyed how he went into some detail regarding how this simple view of nature (what he calls "Atoms and the Void") is at odds against the (secular) Platonic worldview. I believe he does a fair job explaining both views and why a simpler view of nature is preferable.

Anyways, it's hard to say enough about this book. Pick up a copy and enjoy!