Reviewing a high-school physics text

Heath Physics
1992. 848 pages. ISBN: 0-669-25793-1. D.C. Heath and Company,
125 Spring Street, Lexington, Massachusetts 02173.

This Sloppy and Confused Book Is Unusable

Lawrence S. Lerner

Some parts of Heath Physics, especially in the early chapters, are knowledgeable and reliable. The generally fine section on kinematics, for example, incorporates clear description, excellent use of graphs, a judicious use of exercises and worked examples to promote comprehension, and steady progress through the subject matter. Most of the illustrations in this section are good (though Heath's failure to number the figures creates inconvenience and confusion), and some of the laboratory exercises are good, too (even if they seem superfluous in a book that is accompanied by a lab manual).

A good beginning, however, cannot compensate for a bad middle and a worse end. As a whole, Heath Physics is riddled with errors and with dumb, bewildering statements that escaped the editors' notice. As a whole, it is a careless, confused product in which the reliable passages are swamped by mistakes, guesswork and obscurity. It is not improved by the writers' insistence on administering the usual dose of "ecological" piety, though these are offset, to some degree, by a mostly rational discussion of nuclear power.

The book's title page lists five authors but gives only their names. It doesn't tell where they work or what they do. Four of the names are unfamiliar to me, but I recognize the fifth -- Mark A. Carle -- because it has also appeared on the title page of Heath's physical-science book. [See "A Book So Poorly Done That It Should Be Withdrawn" and "Down in the Mud with Mark A. Carle" in TTL for July-August 1991.]

The copyright page says that Heath Physics was "Published simultaneously in Canada," which may account for some of the book's idiosyncracies and inconsistencies. I suspect that Heath first created a book for the Canadian market, then put it through some quick-and-dirty editing to produce a version for sale in the United States -- the version that I am describing here. I see, for example, that the introductory discussion of kinetic energy (page 187) uses references to curling, a sport that is popular in Canada but is seldom seen in the United States. Canadian spellings occur on many pages, and some words appear in both their Canadian and American forms. For instance, the measure of speed is "meters per second" in some places but "metres per second" elsewhere, and an airplane wing is both an "air foil" and an "aerofoil." Such words as "colour," "syphon" and "updraught" will seem odd to students in this country, and so will such phrases as "different to."

Those, however, are only minor displays of the sloppy work that characterizes this book. More serious editorial mistakes are manifested as contradictions and as strange repetitions which suggest that Heath's writers didn't read each other's stuff. For instance, the text says that electrons are emitted with neutrinos but positrons are emitted with antineutrinos -- yet these claims are followed by equations that say exactly the opposite. (Will students know that the text is wrong while the equations are right?) The kilowatt-hour is introduced on page 180 -- and then it is introduced again on page 609, as if it were something new. The concepts of period and frequency are presented in some detail on page 22 -- and then they are presented again on page 309, as if the student has not seen them it before. Even worse, the term optically dense is introduced and defined in the first paragraph on page 465, and then is introduced again in the fifth paragraph on the same page!

I had the bad judgment to make a list of the misconceptions and other faults that I found in Heath Physics, categorizing them as scientific mistakes, pedagogic mistakes, false "historical" claims, and so on. The list eventually filled 23 single-spaced pages. Here are a few items from my catalogue of Heath's scientific mistakes:

• On page 105 the text says that "astronauts on a trip to the moon find their weight slowly decreasing toward zero," and a table purports to show this: It indicates that an astronaut's weight decreases with distance from Earth, that the astronaut becomes weightless when he has traveled 9/10 of the way to the Moon, and that his weight then increases. In reality, astronauts find no such thing; they experience weightlessness during their entire trip, except during the brief periods when their spacecraft's engines are running. Heath's people have everything wrong because they have embraced the "Jules Verne fallacy": Their idea of what happens during a space flight comes from Verne's story From the Earth to the Moon. But Verne was a novelist, not a physicist, and he was writing fiction. If Heath's editors had thought about the meaning of weight, they would not have published this nonsense.

• Page 111: A graph supposedly shows the elongation of a coiled spring as it is stretched to breaking. Beyond the elastic limit, the graph is totally wrong and is implicitly contradicted by the accompanying text.

• Page 129: Heath's writers try to recount the beautiful thought-experiment, involving a rolling ball, by which Galileo justified the law of inertia. They get it tangled up, however, confusing it with Galileo's interrupted-pendulum experiment.

• Page 140: This book's explanation of the tides is the usual one -- lame and inaccurate. Few textbook-writers seem to grasp that what causes the tides is not the Moon's gravitational force, as such, but the gradient of that force.

• Page 144: "When you walk, you push with your feet, but your feet do not push on you." Of course they do. If they didn't, the rest of you wouldn't go anywhere.

• On page 174 the writers say that work is done when a chicken is roasted in an oven. This and numerous other mistakes show that the writers don't understand the first law of thermodynamics. The transfer of heat into a chicken (or anything else) is explicitly not work, and the distinction between heat and work is the main distinction made by the first law. The confusion is reinforced by the claim (on page 181) that "Work is the transfer of energy"; energy may be transferred through work, but it also may be transferred in the form of heat.

• Page 207: The description of the tidal electric-power plant on the Rance estuary is wrong. It is not true that water is trapped at high tide and is released through generators at low tide. The generators are driven by variable-pitch turbines that can operate at any tidal stage. When the tide is high or low, the turbines exploit differences in head; at other times, they exploit tidal currents.

• Page 224: The writers list seven "features" of the "Kinetic Molecular Theory" of heat, but only two of these "features" are essential: A gas is a multitude of molecules that interact weakly or don't interact at all, and the molecules are in motion. The writers say no more about the kinetic theory, and the student must accept on faith the statement that temperature is a measure of the average kinetic energy of molecules (page 228).

• Pages 230 and 231: The writers tell the student to look at a list and "Note that the coefficients of volume expansion for liquids are typically larger than those for solids." But the values given for solids are coefficients of linear expansion rather than volumetric expansion, so the comparisons will be meaningless.

• Page 234: Here the writers refer to "the First Law of Thermodynamics -- also called the Law of Conservation of Energy." This may be the worst "physics" in the whole book. Though the first law is consistent with the conservation of energy, no respectable physicist or chemist would imagine that these two principles are the same thing. Heath's writers have again shown that they don't know what the first law does. It divides all the energy entering a system into two parts: heat and macroscopic work.

• Page 281: The writers discuss the operation of a siphon (or "syphon") as if the underlying principles were poorly understood or controversial. Nothing could be further from the truth -- and the writers' analogy between a siphon and chain moving over a pulley is far-fetched and inaccurate.

• Page 311: Here the writers equate a "pulse" with a "shock wave," though a pulse and a shock wave are not even similar. On page 315 they wrongly apply the name "the wave equation" to an equation that relates a wave's speed to its frequency and wavelength. On page 393 they wrongly use "sound barrier" to denote a shock wave.

• Page 414: "Today we have very accurate measurements [of the speed of light] made with lasers. The currently accepted value for the speed of light in a vacuum is c = 2.997 924 . . . x 10 to the 8^th power m/s." This wrongly tells the student that c is a measured quantity. In fact, c has been a defined quantity since 1983; specifically, c = 299 792 458 m/s exactly. This value of c has replaced the meter as a fundamental unit, and the meter is now a derived unit (expressed in terms of c and the second).

• Page 522: "Rods [in a human retina] are only sensitive to low-intensity light . . . ." Wrong and silly.

• Page 527: The writers say that a spectrometer produces "a pure spectrum." What's that? And why do the writers confuse the terms spectrometer and spectroscope?

• Page 561: In an article on photocopiers, the writers confuse photoconductors with photo-sensitive materials, and the account of how a copier works is wrong. If the drum were to roll directly over the copy paper, the copier would yield a mirror image, rather than a true image, of the original.

• Page 634: "The most up-to-date theory suggests that the Earth's magnetic field is due to the presence of swirling currents of molten magnetic iron in its interior. As this lava flows, the position of the north and south magnetic poles shifts . . . ." In fact, all theories of terrestrial magnetism invoke convection in a conductive core; and though the core is largely iron, its magnetic properties aren't important because its temperature is far above the Curie point. Finally, the core isn't "lava." Lava is molten rock that has risen from Earth's mantle and has been ejected onto the surface of the lithosphere.

• Page 641: Here the writers misstate Oersted's law, falsely call it the "basic principle of electromagnetism," and falsely imply that Oersted was aware of the existence of electrons. Later they misstate Ampère's law and Faraday's law, too!

• Page 746: "Scientists are at a loss to explain exactly why `stimulated emission' occurs." Wrong; stimulated emission is as well understood as any atomic phenomenon that I can think of.

• Page 770: A margin-note says, "Hadrons are nucleons . . . ." No. Some hadrons are nucleons, some are not. In the main text, hadrons and leptons are defined in terms of the strong and weak nuclear forces, but the definitions are useless because the strong and weak forces are never explained. The accompanying diagram is both erroneous and incomprehensible.

• Page 771: "[Murray Gell-Mann] divided his three quarks into flavors, which he called up, down, and sideways, [which were designated by abbreviations]. Later it became apparent that sideways had to with strangeness, but the abbreviation remained the same." What does any of this mean?

The pedagogic defects in Heath Physics include inconsistencies, evasions, questions that involve implausible numbers or situations, and many instances of putting the cart before the horse. Here are a few examples:

• On page 29 a "Discussion" item shows a graph representing uniform displacement, with a cumulative displacement of 3 x 10⁸ meters after 1 second. The student is supposed to tell why this cannot represent the motion of a real object, but the reasons involve the theory of relativity -- a subject that the book has not yet mentioned.

• Page 103: Gravitational force is defined in terms of mass, but the concept of mass hasn't been introduced yet.

• On page 115 and several others, the student finds careless free-body diagrams that don't make sense. Sometimes the individual forces acting on a body are shown as arrows attached to the body, but their resultant floats in space. In a diagram of a parachutist (on page 148), the force of air resistance is shown as an arrow attached to the parachute, but the parachutist's weight is shown as an arrow attached to nothing, and the resultant is shown only as a number.

• A margin-note on page 179 says: "The world's highest free standing structure is the CN Tower in Toronto, Ontario. A record for climbing its 1760 steps was set in August, 1980 by Michael Round who climbed the steps in 10 min and 10 s. Try estimating his average power during the climb." No, thanks. We cannot form even a crude estimate of his average power unless we know his weight and the vertical distance through which he climbed; merely knowing that he climbed "1760 steps" doesn't suffice.

• Page 202: "[Natural gas] is used primarily for home heating and cooking. Of the 18 780 billion cubic feet consumed in this country in 1988, 25% was used residentially." How's that again? How could the primary use account for only 25% of consumption?

• Page 205: A "Practice" problem says: "Describe all the transformations of energy that take place in producing electricity from hydroelectric power." Alas, the student will not have all the necessary information until he arrives at chapter 23, which starts on page 687.

• Page 219: Problem 16 asks the student to "Calculate the work done by a 0.47 N force pushing a pencil 0.26 m." Never mind the work -- look at the acceleration. A typical pencil, with a mass of 5 grams or so, would respond to a 0.47-N force by taking off like a rocket; its acceleration would be almost 10 g. Problem 17 involves a huge pencil whose mass is 26 grams and whose progress is opposed by a frictional force of 0.23 N. The coefficient of friction is therefore about 0.9, which is implausibly high; but even so, the pencil's acceleration turns out to be nearly 1 g.

• Page 247: A margin-note gratuitously introduces the word entropy but doesn't explain it. The writers tell the student to "Ask your teacher what entropy and the Law of Entropy mean."

• In chapter 20 the writers unwisely depart from standard practice and employ a reversed convention for dealing with electric currents: They define the direction of a current as the direction of the electron flow. This convention was adopted by the armed forces during World War 2, for use in the training of electronic technicians, though it is not used in science or engineering. The writers of Heath Physics, however, not only use it but even glorify it: They claim, falsely, that it is "favored by many physicists"! Students will learn otherwise if they go on to study physical science or engineering in college, and they doubtless will have difficulty in learning the right-hand convention for cross products. What Heath's writers have done is a real disservice to students, but it is not unique. I have found the same blunder in Prentice-Hall's Physics: Its Methods and Meanings; see The Textbook Letter, January- February 1992.

• Pages 627 and 628: ". . . Earth's magnetic field has remained quite constant during the seven centuries since the magnetic compass came into use. But the magnetic field is slowly changing?" Well, which is it? -- constant or changing?

• Page 652: Ampère's law is labeled "the motor principle," a bizarre, misleading name that is used throughout the text.

• Pages 655 through 690 are rich in obscurity. The explanation of an electric motor is incomprehensible, and the diagrams are worse. The activity titled "Constructing a Simple DC Motor" is impenetrable. The one-sentence description of magnetic-resonance imaging explains nothing. The text about transformers refers to "mutual induction," but mutual induction is never defined or explained. And so on.

One of the glories of physics is its tight internal logic: Given a few basic laws, everything else seems to follow in a clear, ineluctable way. But of course, that is not how physics developed. Like every other intellectual endeavor, physics has a history marked by blind alleys, misconceptions, partial understandings, and lengthy efforts to find the fundamental rules that lie behind observable phenomena.

You would never deduce this from reading our high-school physics books, most of which have been written by persons who know virtually nothing about the history of science. These writers often invent "oughta-wuz" history. They assume that physics must have developed in a completely logical way, and then they work backward to fabricate events which, they imagine, must have happened or ought to have happened. Here are some examples of the oughta-wuz history in Heath Physics:

• Page 109: The writers claim that Newton the law of gravitation in its modern form, evaluated G, and used SI units. None of that is true, and the earliest ancestors of SI units didn't appear until seven decades after Newton's death.

• Page 131: "Aristotle's description of motion was abandoned primarily because it was not as simple as Galileo's and Newton's . . . ." Wrong. Simplicity had nothing to do with it, especially because 17th-century thinkers offered many different opinions about what was simple and what was complex. The Aristotelian view of motion was abandoned because Galileo's ideas were much more fruitful in suggesting new lines of inquiry and explaining new observations; even Galileo's mistakes (such as his erroneous theory of the tides, and his adherence to the idea that planets moved in circular orbits) were readily corrected by his successors. By Newton's time, the matter was settled.

• Page 207: The windmills that were built in North America in the early 20th century were used chiefly for pumping water, not for generating electric power -- and they did not gradually disappear "as electric transmission lines were extended." Lots of them are still at work.

• Page 234: The long margin-note about James Prescott Joule, William Thompson, and "the democratic world of science" is pious nonsense, and the effort to portray Joule as lowly, humble brewer is silly. Like many British scientists of the 19th century, Joule was a wealthy man -- until he dissipated his fortune in pursuing his experiments.

• Page 390: "The frequencies that are used for musical scales were chosen on the basis of experience and mathematical theory to provide the greatest possible number of pleasing combinations." Double nonsense. The invention of tradition scales had nothing to do with mathematics (though the mathematical relationships in established scales are interesting), and the standard scale used in Western music is not the most pleasing to Western ears; it is a system of compromises, developed in the 17th century, that permits a given instrument to play in many different keys.

• Page 413: Albert Michelson did not invent the rotating-mirror method of measuring c, the speed of light. Nor did his measurements of c bring him a Nobel prize; his Nobel prize commemorated his work in interferometry. Nor did he die before any results were calculated from the experiments that he had performed in 1923.

• Page 595: Even if it oughta wuz, the "discovery of Ohm's Law" was not made by Ohm! The law was put forth (and named for Ohm) by Kirchhoff.

• Page 640: The distinction between electricity and magnetism was known long before "the beginning of the 19th century." William Gilbert recognized it before 1600. In fact, this was his greatest scientific achievement.

• Page 649: "Logic circuits and computers could be built with electromagnetic relays but they would be very cumbersome and slow." This falsely suggests that computers made from relays are merely hypothetical. In fact, relay computers have been built and have been used for making practical calculations. As late as 1953, the Aberdeen Proving Ground employed a relay computer to calculate trajectories.

• Page 712: After describing Thomson's famous e/m experiment, performed in 1897, the writers say that "[Thomson] called this new elementary particle the electron." That oughta wuz, but it didn't happen. First, the name electron had been coined in the 1880s by the Irish physicist G. Johnstone Stoney, who used it to denote the hypothetical elementary unit of negative charge. Second, Thomson was a cautious man, and he was not ready to say that the particles he had found were equivalent to Stoney's electrons. Until 1905 or so, he simply referred to the particles as "corpuscles."

• Page 743: Planck, not Einstein, devised the equation E = hf.

Not all of the fictitious history in Heath Physics is oughta-wuz material. Some of it is just gratuitous silliness:

• Page 132: "[Newton] became very violent whenever his ideas were challenged . . . ." Not so. Newton was egotistical and resentful of rivals, and he could hold grudges, but he was withdrawn rather than violent. History discloses no instance of his reacting violently to anything.

• Page 277: "In 1643, an Italian scientist, Evangelista Torricelli, made one of the first barometers, using water (legend has it he may even have used wine) as the liquid." This bit of ignorance scrambles two experiments and two scientists. Torricelli built the first water barometers, and the behavior of the water in his instruments gave rise to a controversy. Why was there an apparently empty space at the top of the tube, above the water column? Did the space mean that the length of the column was dictated by the pressure of the atmosphere, as Torricelli said? Or did it mean that nature -- abhorring a vacuum -- caused the space to be filled with vapor and thus kept the tube from being filled to the top with liquid? The argument was resolved by Blaise Pascal, using a barometer that contained wine instead of water. Wine is less dense than water because wine contains alcohol, but the vapor pressure of alcohol is greater than the vapor pressure of water. If vapor were preventing the formation of a vacuum, the higher vapor pressure at the top of the wine barometer would depress the liquid column, making it shorter than the column in a water barometer; but if the length of the column depended on the pressure of the atmosphere, the liquid column in a wine barometer would be taller than the column in a water barometer, because wine's density is lower. Pascal observed this latter result, and he thus showed that Torricelli was right.

• Pages 792 and 793: The production of uranium-235 for the first nuclear reactor did not take three years. The production of plutonium was done at Hanford, not at Oak Ridge. And the "cross section of a nuclear fission bomb," on page 793, is all wrong; it doesn't show the geometry of any of the bombs that are described in the text.

Despite all its sloppiness and silliness, Heath Physics does have some good parts. As I said before, the section on kinematics is generally fine. Here are some other items that caught my eye: On page 276, the illustration that shows how to make a mercury barometer is quite clear. On page 283 the discussion of Archimedes's principle is good. On page 291 there is a nice problem in which the student calculates how much Styrofoam must be added to an aluminum rowboat if the boat is to stay afloat when flooded. Page 368 offers a fine experiment in which the student determines the speed of sound by rhythmically clapping two boards together while the sound is reflected by a wall. On page 501, in a passage about the optics of the human eye, the writers properly acknowledge the refractive function of the cornea; unfortunately, the accompanying diagram doesn't show this. The extensive discussion of Kirchhoff's laws, in chapter 20, is welcome; it helps students to avoid the misconceptions that can arise if circuit theory is oversimplified into a mere consideration of series and parallel wiring. And the discussion of nuclear-reactor safety, in chapter 27, is generally well done.

Taken all in all, however, Heath Physics is unusable. I hope that the next edition will benefit from the work of some good editors who can get the existing mess straightened out. Then and only then will Heath have a physics book worth buying.

Lawrence S. Lerner is a professor in the Department of Physics and Astronomy at California State University, Long Beach. His specialties are condensed-matter physics, the history of science, and science education. He served on the panel that wrote the current framework for science education in California's public schools, and he is a director of The Textbook League.

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