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John S. Rigden, Hydrogen : The Essential Element. Cambridge, MA : Harvard University Press, 2002. vii + 280 pages, with notes and index. Illustrated with photographs, charts, and line drawings.
This is a book about the physicists' "hydrogen", namely, the hydrogen atom: one proton, one electron, plus occasional variations (isotopes, molecules, ions, Rydberg atoms). The hydrogen atom is considered (by physicists) the simplest atom, so it has served as the incubator, laboratory, and critical test case for all theories about atoms.
Because the hydrogen atom is central to atomic theory, the hydrogen atom is central to the development of quantum mechanics in the early twentieth century, and a major player in a number of other significant advances, notably radio astronomy, high-precision measurement (particularly of time, with the development of hydrogen masers), and nuclear magnetic resonance (NMR), which later developed into the now-familiar magnetic-resonance imaging (MRI).
I thought that this recounting of scientific episodes in the history of the hydrogen atom was exciting and very engaging. Some of that may be because it's material that relatively familiar to me, but I think even the interest of readers for whom this is new ground will be captured and kept by the author's lively writing, not to mention his own interest in the subject. The author's language is clear and, to his credit, he does not avoid technical terms or the occasional mathematical symbol, but all that's required is a little extra thought to absorb the new ideas as they are presented. Caution: good books about science may require that the reader learn something about science!
The quest for unity is a staple of physics. in the chapters that follow, we shall see that the simple hydrogen atom has been a vital presence in that quest. [p. 18]
The chapters in the book move along mostly chronologically, but that also means moving from one big idea to another. Each chapter had a subheading that named one or two scientists and a year, largely to emphasize how understanding of the hydrogen atom was advancing through a succession of watershed experiments and breakthroughs in theory.
In the early part of the twentieth century it seemed popular for the press, and not a few scientists, to indulge in hyperbole about the inscrutability of "modern physics", that relativity was only really understood by maybe three people in the world, or that no one really understood quantum mechanics—especially if they thought they did!
That was wrong. It was wrong to advance the idea that physical concepts are somehow beyond normal human thought—it's not and it alienates the nonscientist culturally from science. It also was an error because scientists understood perfectly well the theories of quantum mechanics and applied those ideas in adventurous and productive ways, even if they proclaimed themselves baffled by the "nonintuitive" behavior of very small things.
Localization and delocalization express the ideas of discreteness and continuity. The quantum world with its atoms, electrons, and photons is characterized by discreteness. By contrast, the living world, that is, the world of our experience, is characterized by continuity. As we seek to understand the quantum world, we are handicapped because our imaginations are the products of our experience. To our way of thinking, localization (discreteness) and delocalization (continuity) are contradictory. Yet both the electron and light do what they do despite our conceptual chagrin. The electron is just the electron and light is just light. The challenge is to construct a conceptual bridge between these disparate worlds. In 1925 the young German physicist Werner Heisenberg began work on just such a bridge. [pp. 61—62]
The reader of this satisfying historical and scientific excursion gains in both those areas, discovering that concepts from quantum mechanics and the physics of NMR are comprehensible, and making new connections between those concepts and other cultural ideas through the insight that comes from historical insight.
This book was born, however, while I was listening to a talk at a meeting of the American Association for the Advancement of Science. The speaker was expounding boldly on current physics and how a single theory of everything was likely to become a reality. "Come on," I said to myself, "the hydrogen atom, the simplest atom, still beckons. We are still learning from the hydrogen atom" After all, H stands not only for hydrogen, but also for humility. The hydrogen atom still beckons—its story far from over. On occasion we hear that all basic knowledge in science has been acquired. Whenever someone makes such claims, it would be advisable to remember that the simplest atom, one proton and one electron, is still providing insights into natural phenomena. As long as scientists are learning from the essential element, hydrogen, science itself is in no danger of ending. [p. 255]
-- Notes by JNS