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from The Textbook Letter, May-June 1997

Reviewing a high-school book in physics

Conceptual Physics
1997. 692 pages. ISBN of the student's edition: 0-201-46697-X.
Addison-Wesley Publishing Company, Inc., 2725 Sand Hill Road,
Menlo Park, California 94025.

This Redesigned Textbook Is
Marked by Flash and Clutter

William J. Bennetta

Paul G. Hewitt teaches physics at the City College of San Francisco. In Conceptual Physics Hewitt attempts to explain essential principles of physics, to high-school students, while making little use of mathematics.

This is the third version of Conceptual Physics. Like the earlier ones, which were dated in 1987 and 1992, it stands somewhere between a middle-school physical-science text and a standard, formal physics text. Hewitt's prose is friendly, frugal and sometimes playful, recalling the science writing that appears in newsstand magazines, and his narratives will be readily comprehensible, I believe, to any student who has mastered elementary algebra.

The most striking differences between the 1997 version and its immediate predecessor are differences in appearance. In the 1992 book -- which was printed in only two colors -- there were few sidebars or other distracting gewgaws, and the artwork was dominated by Hewitt's delightful sketches, cartoons and diagrams. The 1997 book has new, faddish sidebars and other decorations that clutter the pages; it is full of four-color photographs and other four-color illustrations, including ones that seem to contribute nothing but flash and gaudiness; and it even has some cheesy computer-generated diagrams that, I guess, are supposed to look hip. In my judgment, the 1997 book is harder to read than the older book was, and it lacks the older book's idiosyncratic charm.

The new book's main text shows various changes, but few of these seem to be significant. With respect to scientific content, the 1997 version of Conceptual Physics is essentially the same as the 1992. Hewitt has a good command of his subject, and nearly all the physics in Conceptual Physics is sound.

Sometimes, though, Hewitt goes badly astray. In this context, I must call attention to some mawkish rubbish that he delivers in his first chapter, where he attempts to convince students that there is no conflict between science and "religion":

Science and religion are different. The domain of science is natural order; the domain of religion is nature's purpose. Religious beliefs and practices usually involve faith in and worship of a supreme being and the creation of human community -- not the practices of science. In this respect, science and religion are as different as apples and oranges and do not contradict each other. The two complement rather than contradict each other.

When we study the nature of light later in this book, we will treat light first as a wave and then as a particle. To the person who knows only a little physics, waves and particles are contradictory. Light can be only one or the other, and we have to choose between them. But to the enlightened physicist, waves and particles complement each other and provide a deeper understanding of light. Similarly, people who are either uninformed or misinformed about the deeper nature of both science and religion often feel they must choose between them. But if we have an understanding of science and religion, we can embrace both without contradiction.

The attempted analogy involving waves and particles is clearly desperate nonsense, and it requires no further comment. What does require comment is Hewitt's categorical declaration that one can embrace science and religion at the same time. Hewitt presents this as fact, but it is no such thing. It is a particular philosophical view based on particular conceptions of what "religion" is and of where the boundaries of "religion" lie -- with the boundaries set so that "religion" does not get into the business of explaining the workings of nature.

This philosophical view has been widely accepted in the West, during the past 150 years or so, but the acceptance certainly has not been universal. Is it possible that Paul Hewitt has never heard of fundamentalism? The fundamentalists explicitly reject Hewitt's philosophy, and they explicitly assert that the job of explaining nature lies in the domain of religion. The fundamentalists hold religious beliefs that directly contradict, and are manifestly irreconcilable with, various findings of science. And the fundamentalists assert, quite correctly, that one can embrace their brand of religion or one can embrace science, but one can't embrace both. If Hewitt doesn't know about this, then he has a lot to learn. If he knows about it and has concealed it, then his passage on science and religion is all the more reprehensible.

When I turn from the main text to the sidebars, I find that many of the sidebars in the 1997 book are needless fluff. A prominent exception is the short article called "Scientific Truth and Integrity," on page 171. It deals with pseudoscientific claims that appear in advertisements, and it makes the point that companies often employ true statements to create false impressions. Here are the article's concluding sentences:

An advertiser who claims that a certain brand of cooking oil will not soak through foods is telling the truth. What the advertiser doesn't say is that no other brands of cooking oil soak through foods either -- at least not at ordinary temperatures and pressures. While the facts stated are true, the implications conveyed are not. There is a difference between truthfulness and integrity.

On the other hand, a sidebar that purports to deal with pseudoscience per se (on page 146) is a disappointing exercise in obscurity. Hewitt offers vague generalizations but fails to examine any examples of pseudoscientific scams. An exploration of faith healing would have worked wonders here.

A sidebar titled "Noting Blood Pressure" (on page 275) is both inept and misleading: Its text deals with venous (hydrostatic) pressure while the illustration shows a physician measuring arterial (hydrodynamic) pressure with a sphygmomanometer. And the sidebar called "Atom Migration" (on page 247) is sheer nonsense: A droplet of ink spreads quickly through a container of water because the ink is carried by convection currents, not because the "atoms or molecules in the drop . . . are perpetually moving."

All in all, the 1997 version of Conceptual Physics is a good and useful book, but I am not convinced that, all in all, it represents any actual improvement over the 1992 version. Hewitt and his editors have made their book look flashy and cluttered, but I do not think that they have made it better.

A Lively and Worthy Book,
Despite Some Weak Points

Laurie A. Fathe

The 1997 version of Addison-Wesley's Conceptual Physics, a textbook created by Paul G. Hewitt, replaces the version that was issued in 1992. Conceptual Physics retains its identity as a lively and generally engaging treatment of physics for a high-school audience, even though the new version -- in keeping with one of the current trends in schoolbook design -- has been loaded with four-color illustrations.

The book is organized in a standard way and has six major units: "Mechanics," "Properties of Matter," "Heat," "Sound and Light," "Electricity and Magnetism," and "Atomic and Nuclear Physics." On the whole, the subject matter is explained well, and the physics is sound. Hewitt does not deal with "hot topics" such as lasers, elementary particles, or atomic-force microscopy, but there is more than enough material here. I hope that teachers will judiciously choose from Hewitt's offerings, rather than attempting to charge through all 40 chapters in a single school year.

There are many things to like in this book, beginning with the pictures, cartoons and graphs. These are eye-catching and generally are suited to the text with which they appear, though I've noticed that a few are pointless, baffling or wrong. For example:

Some of Hewitt's explanations of basic physics are wonderful, surpassing those in many higher-level texts. His introduction to centripetal force falls into this category, and so does his discussion of the difference between center of mass and center of gravity. His passages about everyday phenomena -- like his explanation of the "sweet spot" on a tennis racquet, or his account of how an airport metal-detector works -- are good and are likely to arouse the interest of new students.

There are also some things that I wish were different. For example, the book opens with a picture in which a very animated Hewitt -- standing before a blackboard that is covered with diagrams -- declares that "You can't fully enjoy a game unless you know its rules." In another context, this statement might be welcome. But when it appears at the very beginning of the book, it immediately gives the impression that physics is a set of rules to be memorized. This impression is already too common among students, and teachers have to work hard to dispel it.

Hewitt's philosophizing in Conceptual Physics may give some readers pause. On page 1, for instance, he pronounces physics to be "the most basic of all the sciences." On page 7 he tries to turn space vehicles into sacred objects by equating them with cathedrals and other religious structures that people made in earlier centuries. "To the people of that time," he says, "the structures they erected were their `spaceships of faith' -- firmly anchored but pointing to the cosmos." (Really? Did the people who built Europe's great cathedrals really call them "spaceships of faith"? And how can space vehicles serve their purpose if they're "firmly anchored"?) Although Hewitt's aim may be to stimulate thought, I think that he could have achieved this end without inserting so much of his own bias into the text.

The book suffers further when Hewitt, like many other experts, sometimes fails to define his terms adequately. This mistake is especially easy to make when one is writing about physics, because some of the words that physicists use as formal scientific terms (such as work or heat) are words that we all use, loosely and informally, in everyday conversation. The writer of an introductory physics text has to define such terms carefully and repeatedly to make their scientific meanings clear.

Hewitt also lapses into plain sloppiness from time to time. On page 14, for example, he says that "Constant speed means that the motion remains at the same speed" -- a circular statement that doesn't contribute anything to the student's understanding. On the same page, he says that "A body may move at constant speed along a curved path, for example, but it does not move with constant velocity, because its direction is changing at every instant." That may make good sense to a second-semester student, but it probably will bewilder a beginning student who has not yet read anything about the concept of acceleration. (Hewitt begins to introduce acceleration on the next page.) The occasional appearance of obscure phrases doesn't help, either. How many readers of this review understand what tail-end Charlie means?

The matter of language should be paramount in the minds of all writers of science textbooks, the more so because studies such as those done by Elaine Seymore and Nancy Hewitt have shown us that unintelligible writing and the use of "insiders' lingo" is a source of frustration and discouragement among science students. There is no point in producing an introductory textbook that cannot be understood unless its readers are already acquainted with the subject matter -- and by "readers," I mean both students and teachers. Like it or not, the persons who teach physics in many of our high schools were not physics majors when they were in college. These teachers do not possess the thorough background in physics that is required for interpreting many high-school physics texts. (See Talking about Leaving: Why Undergraduate Students Leave the Sciences, by Elaine Seymore and Nancy M. Hewitt, published in 1997 by Westview Press in Boulder, Colorado).

Now and then, Hewitt makes distracting forays down obscure sidepaths. Generally these are harmless, and certain readers may enjoy them, but his long excursion into centrifugal force is a nightmare in the making. By talking about an "outward force . . . called centrifugal force," he firmly plants in the students' minds the idea of a real force that causes things to move radially outward. He makes a weak attempt to explain that this is a misconception, but in the next three pages he does much more to reinforce the misconception than to correct it. Indeed, the mere fact that he presents two sections of text titled "Centripetal and Centrifugal Force" and "Centrifugal Force in a Rotating Frame of Reference" must lead the naive reader to imagine that there exists a real, independent entity called centrifugal force. These two sections are among the few in Conceptual Physics that I would never want my students to see.

Each chapter in the book ends with a review that contains various vehicles to assist students in recalling and comprehending the chapter's material. Typically there is a "Concept Summary," a list of "Important Terms" (which sometimes is so long that it will make the reader wonder whether all of the terms are truly important), then sets of exercises titled "Review Questions," "Plug and Chug," "Think and Explain" and "Think and Solve." Generally, the chapter reviews are valuable and offer more than the usual litany of variations on old problems. I wish that Hewitt hadn't adopted the denigrating phrase "Plug and Chug," which is a bit of student argot connoting mindless, wasteful number-crunching.

Despite my criticisms, I can recommend the 1997 Conceptual Physics as a high-school text. To a great extent it does what it promises to do, which is to deal cogently with physics at a conceptual level, with minimal reliance upon mathematics. It is well organized, it is appealingly designed, and it has plenty of connections between physics and "real life" -- enough to engage almost any reader. I hope that Hewitt, in the next version of Conceptual Physics, will eliminate his occasional lapses into obscure writing, and will put aside the philosophizing that comes from his socialization as a physicist.


William J. Bennetta is a professional editor, a fellow of the California Academy of Sciences, the president of The Textbook League, and the editor of The Textbook Letter. He writes frequently about the propagation of quackery, false "science" and false "history" in schoolbooks.

Laurie A. Fathe is a physicist whose interests include laser physics, science education, and national science policy. She has taught for more than ten years at Occidental College (in Los Angles), and she recently became the manager of the Los Angeles Collaborative for Teacher Excellence. The Collaborative, which is supported by the National Science Foundation, seeks to enhance the education of math teachers and science teachers.

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