Theory and measurement

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scientific reader who has a broad interest in the sea floor environment, E.A. HAILWOOD (Southampton, Gt. Britain)

Physics of Planetary Interiors. G.H.A. Cole. Adam

Huger Ltd., Bristol, 1984, 208 pp., price, hardback, £22.00, ISBN 0-85274-444-4, paperback, £9.95, ISBN 0-85274-444-5. I read this book mainly from the viewpoint of a teacher of geophysics at undergraduate level. For some years I have been looking for a single text which I could recommend to students to help them improve their understanding of the basic physics forming the background to the treatment of a variety of geophysical topics: most of the popular geophysics texts quote the formulae and theorems which they use with little or no explanation. While this approach may be acceptable to students interested purely in using geophysical methods in a rule of thumb way, it is inadequate for those who wish to develop the sound understanding which is an essential prerequisite for carrying out original research or for developing new methods and techniques. Cole’s book fills a gap in the range of available texts in that it obviates the need for the serious geophysics student to have a small library of physics textbooks at hand. His book should, moreover, prove useful to a wider range of students because nowadays many potential honours physics students have an unsatisfactory grasp of classical physics. This situation has developed through the last quarter century due to the slow but unrelenting trend in the content of most undergraduate physics courses away from classical physics, progressively to more and more exotic branches of modern physics. Thus, by the present time, classical physics has become a rather neglected discipline even though the need for physics graduates with a sound grounding in its principles and its applications is still widespread. The requirement for classical physics is by no means limited to geophysicists: many of the outstanding problems of science, particularly where it interacts with tech-

nology, involve classical rather than modern physics for their solution. The ready availability of high powered computers provides the key to gaining a better understanding of the behaviour of complex interacting systems so that the present time is an opportune one for a renaissance of classical physics. Geophysical studies, and in particular the study of planetary interiors (and this is where Cole’s book comes in), •provide a background against which the application of the laws of classical physics can be illustrated in a modern context. Physics of Planetary Interiors is divided into nine chapters. The first presents observational data on the solar system. The second is concerned with the question of why planetary bodies are the size they are and discusses sources of internal energy. The third deals with hydrostatic equilibrium, the differentiation of minerals within planetary bodies and equations of state for the large compressions which exist in their deep interiors. Chapter 4 deals with the shape of planetary bodies and introduces the reader to Legendre polynomials. Chapter 5 is concerned with heat transfer processes and discusses the concept of adiabatic temperature gradients. Chapter 6 deals with magnetic fields, dynamo mechanisms and sources of magnetic energy. The last three chapters of the book discuss, respectively, large planets such as Jupiter and Saturn, terrestrial type planets and planetary bodies cornposed of ice. The points developed are concisely summarized in a concluding section to each chapter. This is followed by comments and some brief discussion of the standard reference works for those readers who wish to probe deeper. K.M. CREER (Edinburgh, Gt. Britain)

Theory and Measurement. H.E. Kyburg, Jr. Cam-

bridge University Press, Cambridge, 1984, 273 pp., bibliography and index, price £22.50, ISBN 0-52124878-7. Studies of the nature of measurement have generated an enormous literature among philosophers of science and philosophically-minded scientists during the past twenty years or so. The present

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text attempts to introduce rigour into the language of measurement by re-casting it in the idiom of axiomatics and mathematical logic and also by subjecting it to a critical philosophical analysis. The latter, however, is heavily dependent on the philosophical commitments of the author, which will now be summarised. Professor Kyburg “...doubts if there are any concepts Instead, there are “...merely down to earth propensities to learn and use language in certain ways”. He assumes that “...no observation or set of observations can be taken as implying a theory... and that a quantitative theory cannot be regarded as entailing any observations or as ruling out any observations”. He is also a conventionalist, which means that scientific theories are regarded as freely chosen definitions or axioms rather than laws legitimised by measurements. Furthermore all measurement and scientific inference is anticipated by and is heavily embedded within theory. It is not uncommon in the philosophy of science for the language employed to cut itself loose from the ordinary meanings intended by the practitioners of the science discussed. There is then a danger that the unwitting working scientist may suppose that the philosopher is speaking to him in his own language. The following quotations illustrate possible instances of such perplexity: .

“In the course of our enquiry, we shall generate five different languages”. .having a length of ir inches may well be exactly the same as having a length of 2 inches simply because there aren’t any objects having either length”. “The temperature of a body is still the equivalence class of all bodies which are at the same temperature as the given body”. “It is already clear that ... temperature is [notl what thermometers measure [nor isi area what the product of length of sides measure”, “We cannot ‘confirm’—nor even definitely test—the hypothesis that expansion of mercury between 0°Cand 100°Cis constant, since all the required measurements are subject to error”.

The author seems to suppose that the language of pure mathematics, and its offspring, symbolic logic, is the only rigorous language in which to talk about measurement. This, surely, is questionable since physicists seem quite satisfied that certain physical properties are accurately measured and

that many quantitative laws are well-confirmed, and they have found a simple and unambiguous language in which to communicate this information. Much could be learned by philosophers, perhaps, by examining why and how this language works so effectively. The gap between the author’s meaning and that of the practioner is most striking in the case of dimensional analysis. We are told that “the set of values of a function is the dimension of that quantity”. This is a very simple definition but it does not seem to agree at all with the meaning employed by the dimensional analyst. The concept of dimensions is indeed very obscure and it might have been unravelled with profit here, but the author appears to regard it as unproblematic. The quantity calculus is just as muddled as dimensional analysis, hut here again it is swallowed whole without any sensitivity to difficulties. We are informed that “...the product of pounds and pounds seems sensible, even though square pounds play no role in physical theory”, and “...square eggs are particularly valuable in the unstable environment of a ship’s galley”. The text is written in a fast-moving, amusing and disarming style. After a piece of particularly tortuous argument we read “whew! this works [but] it is clearly not the way we do things in real life”. Professor Kyburg is obviously a likeable person. I find myself in full agreement with him when he writes, “...measurement consists not in assigning numbers to phenomena, but in specifying the magnitudes they embody Arguing that a profound understanding leads to a greater predictive power, he states that “One thinks of the man with a deep humanistic understanding of the .

past as one who is less surprised than most by the course of present events”. The text brings us up to date on the state of this difficult subject, it discusses the problems of error in great detail and includes an excellent bibliography. What we might ask for in any future publication on the philosophy of measurement is much more effort to clarify obscure concepts before feeding them into the engine of axiomatics and mathematical logic, to where theywhy may lost for ever; a greater effort explain thebeworking language of measurement succeeds so well; an

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attempt to avoid a philosophically-laden account of the nature of measurement; and a detailed historical framework for any analysis of the concepts of measurement. J. ROCHE (Oxford, Gt. Britain)

The International Karakoram Project. K.J. Miller (Editor). Cambridge University Press, Cambridge, 1984, Vol. 1, 412 pp., Vol. 2, 635 pp., price £40.00, US$ 79.50, ISBN 0 521 26339 5.

The International Karakoram Project of 1980 with 73 scientists from China, Pakistan and Britam was the largest expedition to critical research areas organised by the Royal Geographical Society on its 150th anniversary. The two volumes of proceedings are edited by the project leader, KM. Miller, Professor of Mechanical Engineering and Head of Department in the University of Sheffield, who has wide experience of mountains, ice, people and britt~ematerials, Each volume has 34 reports and scientific papers grouped under: Geology, Glaciology, Surveying, Seismology, Housing and Natural Hazards, Geomorphology. Volume I has the proceedings of the International Conference held at the Quaid-i-Azam University, Islamabad, Pakistan, which explains the aims, organisation and methods to be used in the Karakoram field work. Much new material is gathered here, some giving results of very relevant work in other parts of the world. Volume 2 has most of the observations and results from the Karakoram; the proceedings of the International Conference held at the Royal Geographical Society, London. The topographic and seismic surveying is probably of greatest interest to the geophysicist, ranging from the problem of reducing successive ohservations of glacier movement stakes to change in the quoted length of the bar representing the Indian foot and hence change in the resulting spheroid axes and the correction for slope and curvature to the geoid. The field problems were more immediate, as well as getting accustomed to altitude, to bad weather, to fasting porters (it was the Moslem

month of Ramadan) and, most sadly, to the accidental death of one surveyor, ironically the most experienced mountaineer of the group. In 1913 to correct the survey systems of what was then Russia and India, a 480 km long N—S triangulation network was conducted across the Karakoram and Pamirs near the 73 meridian, spanning more than one third of the zone of convergence characterising the collision of the Eurasian and Indo—Australian plates. Movement after 67 y along the Southern half of this link would not be detectable unless the currently expected 4 cm y~ of uniform compression had been much exceeded, perhaps by locally large deformation. The cumulative error of the initial, essentially narrow, triangulation chain, pivoting about a single short base, is calculated as ±1.63 m (106 strain). Measuring angles, and wherever possible, distances, from the old beacon stations and with good fixes at valley sites throughout the season from the Decca Survey JMR-1 satellite doppler receiver, reduced the error over the resurveyed link to 0.52 m. Excessive movement was not revealed by the survey, though there is continuing seismicity in the region. A portable seismic array operated for one month in N. Pakistan recorded 371 local events of which 250 were in the Hindu Kush intermediatedepth seismic zone. By contrast only one intermediate-depth (140 km) earthquake was recorded from beneath the Karakoram Range. Small scale activity suggested active faults. Seismicity in Kohistan appeared confined to the crust. Thirty-three were well-located shallow events, and of three deeper in the 45—65 km range, two were beneath some of the highest topography; Nanga Parbat and Rakaposhi. Depth surveys were made on the Hispar and the Ghulkin glaciers, using an impulse radar icedepth sounding system developed in the Cambridge University Engineering Department and used on their 1977 expedition to Vatnajökull icecap in Iceland. The survey method, the apparatus and the results of the Iceland work are written as separate papers because until this time, impulse radar ice-depth soundings had not been successful in wet ice (ice at pressure melting point).