Subject Grouping: Praxis

by Steven Weinberg, Harvard University Press, ISBN 067400647X, £17.95 (€ 28).

These 23 essays written by Steven Weinberg from 1985 to 1999 make a nice collection around the theme of reductionism. Each is preceded by a page or so describing the context, which is often a valuable addition to the main texts of the essays. Professor Weinberg’s introduction to the set led me to believe that the book would be about facing up to the reality of a neutral universe: Tycho Brahe’s statue looking up to the sky is on the cover. The secondary title is more apt: the majority of the essays are in defence of the scientific approach to understanding our surroundings. Flaws in other approaches, especially constructionist, are pointed out.

Weinberg makes a strong case for reductionism. Phenomena can be explained in terms of others, but these explanations come in a hierarchy, which clearly points back to a theory of everything, as yet to be discovered. Physics is closest to this origin and physicists are closing in.

Not being a physicist myself, I found that many of the essays are brilliant formulations of our understanding of physics, better than anything I have read before. Apart from two more or less political statements, which I felt were out of place, the collection is very homogeneous. However, this is also its weak side: points are necessarily repeated and I will now certainly remember that the Standard Model has 18 parameters that we cannot yet calculate. From 1985 to 1999 many things happened to high-energy physics, such as the cancellation of the Superconducting Super Collider. Unless one knows the dates of these events, it is somewhat confusing to the non-physicist to follow the arguments as there is neither a synoptic nor a statement of the current state of affairs.

One thing I am not so sure of is the “emergence” argument. According to Weinberg, apart from historical accidents (initial conditions), what we observe can be understood exclusively in terms of the hierarchy of explanations, with physics at the root. However, computer simulations (for example of neuronal systems) seem to indicate that more than one underlying “physics” can indistinguishably lead to the same behaviour, by construction. Does that not mean that the mathematics governing this behaviour is independent of those physics? Then there may be independent sciences after all.

My favourite essays are the one in which Weinberg takes the humorous view that non-physicists are somewhat odd, and the 19-page overview of the history of physics in the 20th century. The latter is by far the clearest article on the fundamental ideas behind relativity and quantum mechanics that I have encountered.

The argument that science advances and that it does so independently of the cultural background is certainly in agreement with my own limited experience. Wherever in the world you walk into a university you suddenly feel this, whether lunch is eaten with chopsticks or a totalitarian regime has just been shed.

I greatly enjoyed this collection – it makes me want an entire book in which Weinberg expands on the individual views rather than repeating them in the condensed form of the essays. We need more of this eminently clear exposure of how science works.

by Bernard Pullman (late professor of Quantum Chemistry at the Sorbonne, and director, Institut de Biologie Physico-Chimique, France), Oxford University Press, ISBN 0195114477, £14.95 (€23). Translated from the original French, Editions Fayard, ISBN 2213594635, 729.3.

“This book endeavours to describe the turbulent relationship between atomic theory and philosophy and religion over a period of 25 centuries,” states the preface – a daunting task by any standards. Pullman admits that he is neither a philosopher nor a man of religion, but a chemist “having long lived side-by-side with atoms”. As such, he achieves a great deal.

The book begins with the birth of the atomic theory – the “Greek miracle” of the 7th-5th centuries BC in Pullman’s words, when a few Hellenic thinkers shed the Greek pantheon in favour of a natural philosophy. This began with theories advocating various primordial substances – water (Thales), air (Anaximenes), fire (Heraclitus) and earth (Xenophanes) – from which all things come to be. The two fundamental concepts of atomism – impenetrable, indivisible (atomos) corpuscles and void through which they travel – were formulated around 450 BC by Leucippus and Democritus, and refined a century later by Epicurus and Lucretius to a logical structure that remained essentially unchanged for the next 2000 years. The book also touches on Hindu and Buddhist atomism, which evolved independently at about the same time, but had no impact on the atomic theory of the Western world.

The book then moves on to “a few scattered revivals” during the 1st-15th centuries AD. After describing the antiatomistic position of the Church as put forward by Basil of Caesarea, St Augustine and Thomas Aquinas (among others), some mediaeval Christian atomists make an appearance. These are divided into chroniclers (such as Isidore de Seville), sympathizers and proponents. The sympathizers include Adelard of Bath (a translator of scientific Arab texts) and Thierry of Chartres (a reviver of the works of antiquity). Among the proponents are Constantine the African, a physician from Carthage who explicitly defined atoms as the fundamental constituents of substances; William of Conches; and William of Ockham.

Jewish philosophy from the 9th to the 13th centuries is discussed. This was largely opposed to atomism, although Moses Maimonides (1135-1204) described the teaching of the Arab atomists. The schismatic Jewish sect of the Karaites (founded in the 8th century) adopted the atomic theory borrowed directly from teachings of Muslim philosophers and theologians.

While Greek atomism was to free mankind from invisible powers, Arab atomism is decidedly religious in nature. The Arab atomic doctrine is expressed in the Kalam, a set of 12 propositions, one of which introduces the notion of “accidents”. These reside within atoms, and include characteristics such as life and intelligence, along with inanimate properties such as colour and odour.

Moving into the Renaissance and the age of enlightenment, Pullman describes the resurgence of atomic theory starting with Pierre Gassendi, who is counted among the Christian atomists along with the likes of Galileo, Bruno, Newton and Boyle. Gassendi criticized Aristotle and defended ancient atomists, especially Epicurus, whose teachings he tried to make acceptable to the Church. The doctrine of John Locke, who doubted any future experimental proof of the existence of these atoms, is labelled “agnostic atomism”. Pullman also discusses Maupertuis and Diderot, with their sensitive and intelligent atoms; Holbach, with his materialistic atoms; and Maxwell, who believed that atoms exist due to the action of a creator.

Christian antiatomists – philosophers or scientists who use religious arguments to reject the theory – include Descartes, who rejected the concept of void; and Leibniz with his metaphysical atoms (monads). Others mentioned are Roger Boscovitch, who tried to blend Leibniz’s monads with Newton’s laws of attraction and repulsion; George Berkeley, who rejected matter, material corpuscles and void; and Immanuel Kant, who is labelled an “atomist turned antiatomist”.

The final part of the book moves into the modern era with the advent of scientific atomism through the 19th and 20th centuries. Pullman begins with the demise of the 2000-year-old theory of four elements by the demonstration of Lavoisier that water, and of Cavendish and Priestley that air, have a compound structure. Elements came to be defined as substances that could not be decomposed. Confusion over nomenclature followed until Canizzaro formulated a distinction between atoms and molecules in 1860. Soon afterwards, Mendeleev arranged the first 63 elements in the periodic table.

Controversy, however, continued. Philosophers such as Hegel and Schopenhauer were both opposed to atomism. So were die-hard antiatomists like Berthelot, Mach and Ostwald, and a few that Pullman calls “nostalgic philosophers”, such as Nietzsche, Marx and Bergson.

Nevertheless, atomic theory was almost universally accepted by the time J J Thomson discovered the electron in 1897, bringing the hypothesis of indivisible atoms to an end.

Pullman then brings us into the quantum age in 1900 with Planck’s famous constant. He guides us through Rutherford’s 1911 conclusion that atoms are mainly vacuum with a tiny nucleus surrounded by electrons, to Bohr’s 1913 observation that Planck’s constant leads to stable orbits in the atom and to discrete spectral lines. The rest of the modern atomic picture is carefully covered, with Chadwick’s 1932 discovery of the neutron; de Broglie’s postulation of the wave-like character of matter particles, and its subsequent confirmation by Davisson and Germer; and Schrödinger’s wave mechanics leading to serious conceptual difficulties among scientists.

Chemical bonding naturally plays a large part in the book, given that its author was a chemist. Covalent bonding, where electrons are shared between atoms, leads Pullman to an interesting analogy developed in the chapter “Society of atoms: marriage”, where he concludes that “as always in life, this implies the ability and even obligation both to give and to receive”.

In a closing chapter, Pullman delves into the nanoworld. Here he describes how the scanning-tunnel microscope and the atomic-force microscope led to visualization and manipulation of single atoms interacting with bulk surfaces, and how complete isolation of single (charged) atoms surrounded by vacuum was accomplished using ion traps.

No-one can contest that the atoms conceived 2500 years ago as invisible and indivisible impenetrable philosophical constructs have today become divisible and visible objects of reality. But are they really in human thought? They are certainly in the thoughts of scientists and philosophers, but I doubt they are uppermost in the minds of most people, as Pullman suggests when he claims that “quantum physics has stoked an interest in the ‘problem of God’ among a general public”. The book is let down by its index, which is difficult to use and occasionally inaccurate. That said, however, to read this book is a fruitful learning exercise, and it has a host of informative notes.

by Andrew Holmes-Siedle and Len Adams, 2nd edn (2002), Oxford University Press, ISBN 019850733X, £65 (€102).

This book is aimed at specialists – engineers and applied physicists – employing electronic systems and materials in radiation environments. Its prime role is to explain how to introduce tolerance to radiation into large electronic systems. The reader is expected to be familiar with the theory and operating principles of the various devices. The book mainly addresses components used in space, but also discusses issues specific to other fields, such as military and high-energy physics applications.

The book starts with a quick overview of radiation concepts, units and radiation detection principles, followed by a brief review of the various radiation environments likely to have a degrading effect on electronic devices and systems as encountered in space, energy production (fission and fusion), high-energy physics and in military applications (nuclear weapons). This is followed by a chapter dedicated to a general description of the fundamental effects of radiation in materials and devices: atomic displacement and ionization; as well as colourability of transparent material, single-event phenomena and other transient effects.

Seven central chapters form the core of the handbook, addressing in detail the mechanisms responsible for the degradation of performance of various devices. Each chapter is dedicated to a class of devices: MOS; bipolar transistors and integrated circuits; diodes and optoelectronics such as phototransistors and CCDs; power semiconductors; various types of sensors; and miscellaneous electronic components. The physical problems of total-dose effects and how to predict the electrical changes caused in MOS devices are discussed, along with some of the best solutions to the radiation problem. Long-lived effects, which can be separated into surface and bulk mechanisms, of various radiation types on bipolar transistors are described. How these effects influence the radiation response of bipolar integrated circuits is discussed. The response of the many different types of diodes to radiation is thoroughly discussed in a dedicated chapter. Optoelectronic devices in a hostile environment are subject to multiple effects, and radiation can cause mulfunctioning in a highly tuned, high-technology system. Silicon power devices used as regulators in power subsystems of large space equipment, radiation-generating equipment and nuclear-power sources also suffer from radiation damage. One chapter is devoted to discussing the physics, chemistry and practical problems associated with windows, lenses, optical coatings and optical fibres. Another chapter concentrates on the effects of radiation on polymers and other organics, classifying the main forms of organic degradation under irradiation and summarizing some of the most important examples and problems met with polymers in engineering and science.

Two chapters are dedicated to aspects of radiation shielding of electronic devices and various computer methods for particle transport, essentially with reference to space applications (very thin shields). The three final chapters discuss radiation testing, equipment hardening and hardness assurance. Radiation testing is made unavoidable by the variability in the sensitivity of semiconductors and electronic devices to radiation, which makes it impossible to rely on theory alone to predict the effect on a device of a certain exposure to a given type of radiation. The authors provide guidelines on radiation sources that may be used in irradiation tests, in test procedures and in engineering standards. Finally, they discuss the technologies and methodologies employed in fabricating radiation-hard devices, as well as providing rules of hardening against various types of radiation and for various applications, including remote handling equipment and robots.

Each chapter ends with a summary of its most important points. Besides the usual subject index, a useful author index helps greatly in searching through the large number of references provided at the end of each chapter. With respect to the first edition (1993), the book has been enriched with many references to useful websites, including databases. Surprisingly, the old units rad, rem and curies are used throughout the book, although SI units are provided in brackets. The authors admit they thought hard about what to use, and finally opted for the old system.

It is unfortunate that this otherwise excellent volume contains, here and there, a number of typographical and punctuation errors, and mistakes in some formulae. In a few cases there are contradictory statements a few paragraphs apart. The impression is that the text was not proofread carefully enough before going to print. There are also a few statements that are clearly wrong, such as that X-rays and gamma rays leave no activity in the material irradiated (what about photonuclear reactions above a given threshold?); and others that are confusing, such as in discussing the whole-body dose limit for members of the public. In general, activation phenomena and related problems are also somewhat generally underestimated throughout the book.

Nevertheless, this volume contains a lot of valuable material and is not only a handbook, but also an excellent textbook.

by Jonathan Allday, Institute of Physics Publishing, ISBN 0750308060, £16.99 (€27).

This edition is a revised and updated version of the King’s School, Canterbury teacher’s popular high-school introduction to particle physics and cosmology.