Quantum mechanics, relativity, and their progenies of particle physics and modern cosmology continue to intrigue and baffle students, working physicists, and laypersons alike. In the century since modern physics began, progress has been astonishing, and some current ideas seem as outlandish as the probabilities that so disturbed Einstein in the 1920s. What were once idealized textbook examples or hotly debated theories (quantum wells, entanglement, and gravitational waves) are now the subject of precise and sometimes incredibly expensive experiments, have garnered Nobel Prizes, and even become mass-market technologies. In this collection of essays, Massachusetts Institute of Technology particle physicist/cosmologist and historian of science David Kaiser takes readers on an engaging and informative tour through the quests of twentieth-century physicists to understand space, time, and matter at its most fundamental levels. Kaiser does not try to teach his readers physics; rather, the emphasis is on the connections between scientific exploration and the human condition as viewed through the lives of individual scientists and how they were influenced by the times and places in which they worked, political externalities, collaborators, and evolving institutional priorities. Scientists too are embedded in their cultures.

Kaiser divides his 19 essays into four sections plus an Introduction; there is also a charming Foreword by Alan Lightman, who remarks that the human drive to find patterns may be what holds off insanity. For readers who wish to dig into more background, over 40 pages of notes list a wealth of source material. Most of the essays appeared in other books and articles (notably the London Review of Books), but having them gathered into one place will bring them to the attention of a much broader audience.

In his Introduction, Kaiser explains that by “quantum legacies,” he has in mind the development of shared understanding that emerges between individuals and across generations. Some of these legacies are explored by examining the efforts of individuals and small groups of collaborators, while others involve the influences of machines such as enormous accelerators and programmable computers, and yet others are entangled with institutions and government agencies. The essays could be read at random, but are best taken together in their respective sections.

Kaiser's sections are Quanta, Calculating, Matter, and Cosmos. In brief, Quanta focuses on discrete moments in the transformation of understanding of the microscopic world from the 1920s onward; here we encounter, among others, Dirac, Einstein, Schrödinger, Pontecorvo, Pauli, Fermi, Bell, and Zeilinger. Calculating is not about computing per se, but about how and why the young people of new generations became physicists within the United States during and after WW II, influenced by the Manhattan Project and generous government funding, even while they “learned to calculate” as new technologies emerged. Matter brings the story back to efforts to understand the subatomic realm, with external influencers being the machines of big science; here Peter Higgs is the main personality. Cosmos examines steps in the development of modern cosmology as it grew from being regarded as a slightly disreputable area into a precision science, where cyclic multi-dimensional universes and SETI are topics of serious analysis. The landscape runs from the subatomic to the cosmological, but with human beings always in the foreground.

Kaiser touches on seemingly everything from the sophistication of modern creationist movements to Hawking radiation. Rather than dissect each essay, I will focus on a few items which particularly caught my attention. I especially enjoyed those in “Calculating,” which describes the post-war training of physicists in the United States. In effect, this was the educational analog of a classic economic bubble. Overhyped and careless misinterpretations of studies of Soviet training of scientists and engineers led to fear of a manpower gap, which universities were happy to exploit to rake in funding. Ironically, US graduation rates for scientists and engineers were actually ahead of those of the Soviet Union, as well as programs being far ahead in quality. As with any bubble, the bottom inevitably fell out; the crash began about 1970 with funding cutbacks and growing opposition to the Vietnam war. A second bubble emerged in the 1980s when the National Science Foundation warned of another looming manpower shortage, coupled with increased defense funding during the Reagan administration. The breakup of the Soviet Union prompted another crash, which took the supercollider with it. Supply side boosterism disconnected from reality is not limited to just the latest marketing gimmick or questionable investment.

Tied to enrollment booms and busts is an interesting survey of the evolution of the teaching of quantum mechanics in the United States as reflected through generations of textbooks. In the early (pre-war) days, there was considerable emphasis on interpretive and philosophical issues, but with the postwar boom in enrollments and emphasis on applying physics to national defense issues, attention focused much more on practical calculation-grinding training of quantum mechanists, illustrated by the contrasting approaches of texts by Schiff and Bohm. The 1970s downturn and emergence of the new-age generation saw the pendulum begin to swing back, as exemplified by the publication of Capra's The Tao of Physics. Contemporary texts go for more of a superposition of the two approaches; as Kaiser concludes, there is no best way to teach quantum mechanics.

This book is full of striking statistics, commentary, and lovely analogies and metaphors. Some of the latter are Kaiser's own while others are attributed; even if a reader is familiar with the physics, they will help crystallize concepts otherwise known only known through formalities and equations. A sampling: The quarter-century after World War II saw more physicists trained than had been, cumulatively, in human history. Wavefunction collapse is likened to having no definite weight until you step on your bathroom scale. Gluons are elves who skitter around, enforcing symmetry. Entanglement is illustrated by correlated or anti-correlated dessert choices of far-separated twins. Richard Feynman's remark that particle-collision experiments are like hurling two pocket watches at each other and examining the remains to divine the intricate mechanisms that were within cannot help but inspire a vivid image, as does the comment that “As far as a photon is concerned, time simply does not flow.” (Reviewer comment: Does a photon see the entire universe as Lorentz-contracted to a point?) The Higgs field is molasses through which particles attempt to slog. Cosmology is a poor man's accelerator, and has been a succession of seemingly absurd proposals from Copernicus on up. Chandrasekhar's remark that Misner, Thorne, and Wheeler's Gravitation was “… written with the zeal of a missionary preaching to cannibals” has an elegance that most reviewers can only hope to emulate. LIGO is the largest project funded by the NSF, having spawned some 600 dissertations in the US alone since 1992. Every essay illuminates the reader about something.

My only quibbles with this book are that it can be MIT-centric in places, and Kaiser's tendency to dabble in amateur psychologizing. After chiding Dirac biographer Graham Farmelo for speculating that Dirac's personality traits, which would now probably now be regarded as lying on the autism spectrum, were crucial to his success as a physicist, Kaiser goes on in his very next essay to speculate that in the face of a looming world war and genocide, Erwin Schrödinger's thoughts turned to poison, death, and destruction, with the result being his eponymous cat. Later, Alexander Friedmann's cosmologies which emphasized potentially violent change over time are linked to the political tumult of post-World War I Russia.

Overall, however, these are engaging, though-provoking, fun-to-read essays that are compact enough that one can get through several in an evening. They will make you consider familiar physical concepts in new ways. All readers will come away richer in their knowledge of the people and circumstances behind how physics arrived at where it is. You will enjoy this book.

Cameron Reed is the Charles A. Dana Professor of Physics at Alma College, emeritus. He served as the editor of the American Physical Society's “Physics & Society” newsletter from 2009 to 2013, and is currently an Assistant Editor with this journal. His interests lie in the physics and history of nuclear weapons; his book Manhattan Project: Story of the Century was published by Springer in 2020.