Customer Reviews

The Discovery of Subatomic Particles Revised Edition

5 star:		(4)
4 star:		(2)
3 star:		(0)
2 star:		(0)
1 star:		(0)

 

 

I wavered between four or five stars and finally gave the authors, a brilliant scientist, the benefit of the doubt. The book is actually a chronological review of the exploration of the atom. Starting with electricity and the discovery of the electron, we then go on to weighing the atoms to the discovery of the nucleus. A truly fascinating observation of Einstein's work notes that the "energy released by a moving body is larger than when at rest by an amount proportional to the square of its velocity"..e=mc2 was originally expresses as m=e/c2.

After the nucleus we descend further into all the subatomic particles. One must remember that although this book is a revised edition, the 1983 original version seems almost innocent in many of its assumptions. A LONG appendix is provided as much for explanation as for reference.

This book is a deviation from the author's usual books about complex cosmological issues. The Discovery of Subatomic Particles is accessible to anyone, an easy read revealing much about scientific method. It's more a history of how scientists and physicists with rather rudimentary tools devised innovative ways to probe and measure atomic particles with surprisingly accurate results. This book will be appreciated by the mechanically inclined. For the mathematically inclined, you will see in the appendices calculations developed in such a way that requires only a basic background in algebra to understand.

The author guides the reader through the history of processes that refined our understanding of the subatomic world. The subject matter is covered in a logical timeline progression and consistent format. Quantum theory is outside the scope of this book, but Niels Bohr is included in the history for using some of the discoveries to formulate his view of electron dynamics. The reader will gain a higher appreciation of how much can be measured and discovered using the basic tools and instruments available at a given level of scientific development.

Extensive appendices amount to a concise development of fundamental physics, itself creating much value owning this book. My favorite appendix has the author describing how much of Rutherford's formula for the scattering of alpha particles can be derived through simple dimensional analysis, continuing the historic application of basic tools to analyze, measure, and discover subatomic particles. The appendices give the technical details supporting much of the scientific development described so well in the main text. Steven Weinberg's book, The Discovery of Subatomic Particles, is an easy read that can be appreciated by anyone.

In this book we see the older Weinberg who still
thought in terms of mathematics and experiment
and not in terms of defending his theories
against an uncertain future.
This book I can give to the younger generation in conscience
and say : be wise and read this and learn.

Steven Weinberg was awarded the Nobel Prize in Physics in 1979. He is a prolific writer and has published a number of "industrial-strength" physics texts. This book is intended for a general audience. It details the historical evolution of scientific discovery of the fundamental building blocks of matter - electrons, protons and neutrons.
Only one chapter of 14 pages deals with quarks and leptons, so the title is somewhat misleading (hence 4 stars).
Nonetheless, the historical narrative in this book is fascinating and would be of interest to laymen, physicists, chemists, and engineers. The experimentation upon which atomic theory is built is discussed in detail and the evolution of the periodic table would be of particular interest to chemists. Weinberg fleshes out the science with a delightful discussion of the characters and institutions that played a central role in this endeavor. A SPECIAL NOTE TO FEYNMAN DEVOTEES: Steven Weinberg writes with the same sense of wit and wonder that were the hallmarks of America's favorite bongo player, safecracker, and quantum electrodynamicist. If you liked Richard you'll like Steven.

If a general reader were to take an interest in physics, and had time to devote to only a few books, this one by Professor Weinberg would be very near the top of the list. (this review pertains to the softcover edition published in 1990. about the only major change since then I am aware of is that the neutrino has been found to possess a small nonzero rest mass.)

Ironically, Weinberg is a theoretical physicist (winner of Nobel Prize for his seminal contributions to the modern theory of the weak force and the Standard Model). Yet his book details the series of experimental discoveries in atomic and sub-atomic physics made (mostly) at the Cavendish Laboratory in Britain in the early 20th century.

Weinberg begins chapter one with the historical notion of the atom, and also gives its modern understanding, which is the main concept to be developed throughout the course of the book. Then he introduces the setting of most of the book's action, the Cavendish Laboratory at Cambridge UK. For nonscientists, he presents a summary of units of scientific notation, which will be indispensible.

Chapter two introduces the electron and its discoverer, J.J. Thomson. In a five-and-a-half "flashback" section (one of several in the book), he explains how the concept of electricity first arose back in ancient Greece and medieval Europe and proceeds with its historical development through the time of Ben Franklin up to Thomson's time. He notes that even today, triboelectricity is not well understood. Then electrical discharges produced in cathode ray tubes are presented as the first devices that could allow systematic study of electric currents. Even these were not well suited until effective vacuum pumps could evacuate the tubes sufficiently to eliminate the spurious effects of electron collisions with stray air molecules in the tube. It was noted that the glow and its shadows could be deflected by magnets and electrically charged plates, indicating that the rays were charged particles.

Turning to Thomson's mathematical analysis of these projectiles, Weinberg goes into another four-page flashback to present the basics of Newton's laws of motion, then he takes up the thread again with Thomson's mathematical treatment of the deflection of cathode rays. He relates "Unlike the electric force, the magnetic force acting on a particle is proportional to the particle's velocity as well as to its electric charge. Therefore, the displacement of the ray by magnetic forces depends on a different combination of ray-particle parameters than the displacement due to electric force. By measuring the deflections due to electric and to magnetic forces, Thomson was able to learn the values of two different combinations of ray-particle parameters, and in this way he could determine both the ray-particle velocities and the ratio of their charge and mass."

In another flashback, the facts of life pertaining to the electric force is presented (four and a half pages), then on to electric deflection of cathode rays, and a six page flashback on the magnetic force, and then the magnetic deflection of cathode rays. Finally, the results of Thomson's analysis is presented.

Here Weinberg has to start over once again, as Thomson was not completely satisfied with his analysis of cathode ray deflection (although the data presented is reasonably consistent and convincing). "He also employed another method based on measurements of heat energy deposited at the end of the tube." Now Weinberg goes into a four and a half flashback to present the basics of the concept of energy, and then Thomson's results of this energy relations-based analysis. "The cathode ray was directed into a small metal collector that would capture the electric charge of the ray particles and would also capture their kinetic energy, converting it to heat. The ratio of the heat energy and electric charge deposited in the collector then gives the ratio of the kinetic energy and the charge of each ray particle...Thomson had no idea of the detailed physical processes that occur when a cathode ray hits a metal collector, but he could be confident that the increase in heat energy of the collector had to be equal to the kinetic energy lost by the cathode-ray particles when they were stopped by the collector."

Finally, the idea of the cathode ray particles, now known as "electrons", as elementary particles, concludes chapter one. "There was no way the existence of smaller particles within the atom could be verified on the basis of Thomson's 1897 experiments. Thomson did not claim that he had proved it, but there were a number of hints that led him to his far-reaching conclusions. The first was the universality of the measured ratios of mass to charge, [which] did not seem to depend on any of the circumstances under which it was measured...Thomson also quoted a result of Zeeman that indicated similar values of mass/charge ratio that characterized the electric currents in atoms that are responsible for the emission and absorption of light." In a two page flashback the Zeeman effect is explained. Further, evidence indicated that the cathode ray particles bear similarities to the particles produced by the photoelectric effect, and their charges are of similar magnitudes to the ions produced by electrolysis. Although Kaufmann produced more accurate results than Thomson in similar experiments, only Thomson took the bold step of proposing the cathode ray particles as fundamental constituents of the atom because, not being an adherent of the "Vienna Circle" or applied logical positivism, "he [Thomson] thought it was part of the business of physics to discover fundamental particles."

Chapter three, "The Atomic Scale", greatly broadens the range of topics covered. Weinberg makes the point that Thomson was unable to measure the charge or mass of the electron, only their ratio. Weinberg upps the stakes of the investigational effort by stating that "The physicists and chemists of the 19th century had measured a great many other ratios of atomic properties...All that was needed was one good measurement of either the charge of the electron, the mass of the electron, or the mass or volume of any single atom, and all these ratios could be converted into values for the mass of the electron and the charge of the electron and the mass and volume of every sort of atom. In short, the scale of all atomic phenomena would then be known." In my words, the very linchpin of atomic and molecular physics!

In this chapter we get flashbacks on the foundational concepts of chemistry: atomic weights, Avagadro's molecular concept, and electrolysis. Then Weinberg proceeds with the work of Townsend and Wilson, with water droplets, which led directly to Millikan's measurement of the fundamental electronic charge with droplets of mineral oil.

Chapter four, "The Nucleus", starts with the question of the source of the positive charge within the atom that is necessary to cancel out the negative charge of the electrons in order to make the atom electrically neutral. Thomson's own "plum pudding" model and Nagaoka's "Saturnian" model are suggested as candidates. But Weinberg must, of course, start at the beginning, and for the atomic nucleus, that was the discovery of radioactivity by Becquerel. Here Rutherford himself enters the picture, with his and Soddy's investigations of the alpha, beta, and gamma nuclear radiations. Weinberg goes into their discoveries of elemental transmutations, decay series, the displacement laws, elemental half-lives, and the particle characteristics of the three main nuclear radiations: alpha particles being essentially helium nuclei (and radioactive substances being strongly associated with helium gas), beta particles being the same as electrons, and gamma rays being high-energy light rays (the term "photon" was not then invented). Most astonishing about radioactivity were the calculations of the enormous energies that were being liberated. Even our friend Albert Einstein enters the picture here with the cameo appearance of his E=mc2 energy-mass equation, as it relates to the changes in atomic mass and the resulting liberation of energy in radioactive nuclei.

At last we come to Rutherford's famous scattering experiment conducted by his students Geiger and Marsden, which revealed the atomic nucleus. Weinberg describes the surprising large-angle scattering of alpha particles by gold nuclei, and how Rutherford's interpretation of it led to his conclusion that a massive, positively charged particle called the nucleus dwells at the center of the atom. The correlation of atomic number with atomic weight comes next, followed by the explanation for variations in atomic weights among the elements; in other words, the isotopes. This, of course, brings us to the question of the internal constitution of the nucleus itself. The first step in this investigation was the discovery of the nuclear disintegration of nitrogen nuclei due to Rutherford, and his speculation of a neutrally-charged nuclear constituent. This, of course, brings us to the discovery of the neutron by Chadwick, accomplished due to his experiements with the beryllium rays. At last, Weinberg takes up the issue of the neutron as a fundamental particle. "For Chadwick, as for Rutherford, the neutron was merely a composite of a proton and an electron...It is difficult to pinpoint the moment at which the neutron became accepted as a fully accredited elementary particle." Weinberg explains the facts confounding this concept: the molecular spectra of the nitrogen molecule, the source of the beta particles in nuclear transformations (Fermi's theory of the weak force), and ever-finer measurements of the nuclear masses and the strong force (through nuclear scattering experiments). This chapter closes with a discussion of the map of the isotopes of all the elements, and how their lifetimes and stabilities vary with their binding energies and proton-neutron ratios.

The concluding chapter, "More Particles", goes on to describe, in summary fashion only, subsequent discoveries in subatomic physics. These include: photons, neutrinos, the positron and other antiparticles, the "heavy electrons" (muon and tauon), the pion and the other mesons, the "V-particles" or strange particles (now known generally as hyperons), and the quarks. In the case of the neutrino, Weinberg briefly explains the problem of the missing energy in beta decay, and how it caused Pauli to hypothesize the neutrino, and how Fermi incorporated it and the new weak force into his theory of beta decay. In the case of the positron, Weinberg briefly explains how Dirac's relativistic quantum equation for the electron caused him to hypothesize the existence of positive energy states for the electron, which was confirmed by Anderson's discovery of the positron.

Now, the reason I'm outlining the book in such detail is because I wish to emphasize the depth and breadth of Weinberg's coverage of these foundational principles. He introduces the history of each supporting concept from its very beginning and develops their evolutions from one idea to the next. The mathematical treatment is detailed and extensive, but totally arithmetic and algebraic -- no calculus! More exhaustive treatments are referred to in the book's 36 pages appendices, and again here no calculus! The most advanced math are the logarithmic and tangent functions. Weinberg takes care to make clear the units of measure involved with each equation presented.

Each idea and the work of the entire community of physicists are explained in terms of the preceding ones, making clear how they interrelate and support one another. The narrative touches on so many foundational principles of physics so as to recommend itself as an outstanding way to introduce oneself to them.

More than that, Weinberg makes plain the trains of thought that led the physicists to their hypotheses and interpretations of their experimental results. When you're a theorist, all you really need to know is theory (though of course being informed by experimental methods can only be helpful), but if you're an experimental physicist, you have to be good BOTH with your hands, and at the blackboard as well! Weinberg's presentation makes this fact stand out in stark relief.

One thing I like about Weinberg's narrative is his awareness of the counterfactuals. When reading any history, it is all too easy to overlook the unknowns the principals had to confront in their thinking, and the choices they had to make. We now know that atoms are made of nuclei and electrons, and nuclei are made of protons and neutrons, and nucleons are made of quarks, etc. etc. But when these men were first looking deep into the atom with their primitive instruments, they had no idea of what they were looking for. Says Weinberg, "This totting up of evidence gives an altogether misleading impression of the easiness of Rutherford's task in explaining the large-angle scatterings. A great many wrong explanations must have passed through his mind." Weinberg also mentions difficulties in separating facts from confusing complications. "Rutherford concluded that the particles responsible for the scintillations were the nuclei of hydrogen, which we now call protons. However, he did not know whether these protons were just recoiling nuclei from hydrogen atoms that happened to be present on the metal source and were struck by alpha particles, or whether they were actually knocked out of elements heavier than hydrogen."

The book is replete with drawings, diagrams, and photographs.

As a detailed technical and conceptual history of atomic and sub-atomic physics, Weinberg's book stands, in my opinion, unrivalled. He explains its development with a thorough yet not-too-thorough mathematical treatment. This book has something for everyone whether they want to understand the experiments or the historical development of modern particle physics. As an introduction to the foundational concepts of physics, its breadth and depth recommends itself especially to the student physicist.

This is to alert the reader to the fact that Amazon is mistakenly attributing "The Discovery of Subatomic Particles" to the wrong writer. The author of this history is, of course, Steven Weinberg (no middle initial), who is also the author of several other books for the general reader, including "Lake Views," "Facing Up," "Dreams of a Final Theory," and the earlier "The First Three Minutes." Weinberg has also written the recent treatise, "Cosmology," and the three-volume treatise on "The Quantum Theory of Fields." Steven Weinberg has no middle initial. Perhaps in reviewing this comment, Amazon will correct the error.