more about me
The recent publication of the seventh book of my experimental and theoretical researches, A Certain Uncertainty: Nature’s Random Ways (Cambridge, 2015), closely followed by the newly released Second Edition of my first book, And Yet It Moves: Strange Systems and Subtle Questions in Physics (Cambridge, 2015), has motivated me to look back over a long career as a physicist and educator. From the time I was a child, absorbed in the books of James Jeans, Arthur Eddington, George Gamow, and other physicists and astronomers, to the present day, I have always been fascinated by the intricacies of physical phenomena and driven to understand their underlying causes. There was never any doubt in my mind as to what I wanted to do with my life. And so, I became a physicist (Ph.D. Harvard University). Working primarily at academic institutions, I have had the good fortune to be able to research whatever problem interested me—and in the course of a long career I have chosen eclectically.
I started out in atomic physics, working on a method to study short-lived excited quantum states of neutral atoms by first accelerating the ionised atoms to a high speed and then passing them through a target whereupon they were neutralised, excited, and transported to a chamber downstream for spectroscopic observation. Employing this method on hydrogen, the simplest atom of the periodic table, I investigated quantum electrodynamics (QED), which provides a theoretical description of all known electromagnetic processes with breathtaking accuracy, as confirmed by experiments of truly awesome precision. Non-physicists might find dull the endeavour to measure some physical quantity to high precision, but it is the discrepancy between careful measurement and theoretical prediction that guides physicists to the next level of understanding of how nature works. We know now, for example, that QED is but part of a more inclusive theory that encompasses the weak nuclear interactions in addition to all electromagnetic phenomena.
The physicist who, more than any other, served as my role model was Nobel Laureate Enrico Fermi, a man as adept with theory as he was at home in the laboratory. Like Fermi, I wanted to do both theoretical and experimental work with comparable facility, an ambition not common among physicists. Thus, for example, prior to and during my experiments on the hydrogen atom, I also developed a comprehensive quantum theory of single- and multi-photon interactions of atoms with radiofrequency and microwave fields. A part of this research particularly significant to precision atomic spectroscopy was my generalization to finite-lived excited states of the theory of “separated oscillatory fields”, initially developed for infinitely long-lived states by Norman Ramsay who eventually received the Nobel Prize in Physics for his work. My theoretical and experimental work in atomic physics was eventually published as my fourth book, Probing The Atom: Interactions of Coupled States, Fast Beams, and Loose Electrons (Princeton, 2000). The title, a lightly mischievous play of words, was inspired by the originally conceived title “Base Pairs” of James Watson’s famous book.
In the years that followed, quantum physics constituted a significant part of my research. I investigated a broad spectrum of intriguing quantum phenomena in a wide variety of ways—with electron interferometry, electron microscopy, radiofrequency and microwave spectroscopy, coherent laser spectroscopy, nuclear magnetic and electron paramagnetic resonance, atomic beams, radioactive nuclei, and of course pencil, paper, and computers. One of the most satisfying experiences of this phase of my career resulted from the time I spent in Japan as Visiting Chief Researcher at the Hitachi Advanced Research Laboratory near Tokyo. At Hitachi, I proposed to the electron microscopy group an experiment to demonstrate the buildup of an electron interference pattern one electron at a time. This classic two-slit interference phenomenon—which is one of the most dramatic illustrations of the wave-particle duality of nature—was designated in 2002 the “most beautiful experiment in physics” by readers of Physics World, the flagship publication of the Institute of Physics. My investigations of quantum mechanics became the subject matter of my second book, More Than One Mystery: Explorations in Quantum Interference (Springer, 1995) and sixth book, Quantum Superposition: Counterintuitive Consequences of Coherence, Entanglement, and Interference (Springer, 2008).
Being fascinated with the behaviour of light from childhood onward, I have also done extensive research in physical optics, conducting and analysing numerous experiments on the reflection, refraction, diffraction, interference, polarisation, and scattering of light. For example, using polarised light and a device known as a photoelastic modulator, I devised a method for detecting and imaging hidden objects immersed in a light-scattering medium of the opacity of whole milk. The same methodology made it possible to observe and measure for the first time the difference with which a naturally chiral substance reflects left and right circularly polarised light, thereby completing, in a sense, the epochal 19th Century work of Augustin Fresnel, who first demonstrated the difference with which a chiral substance refracts circularly polarised light. A chiral molecule is one which is not superposable on its mirror image, just like a right-handed glove cannot be superposed on a left-handed glove without turning it inside out. Since molecular chirality is the hallmark of all life on Earth (and probably elsewhere as well, although this is just speculation for now), my research provided a versatile new way to explore systems critical to biology and medicine, as well as materials science. In another phase of my optics work, I devised a method of lensless diffractive imaging by which to isolate and project symmetry patterns from a complex object with high noise content. Since no lenses are used, this method of imaging can be useful for structure determinations with spectral sources for which effective lenses may be difficult or impossible to produce, such as in X-ray and neutron diffraction. I described these and other optical investigations in my third book, Waves and Grains: Reflections on Light and Learning (Princeton, 1998).
From about 2000 onward, I became interested professionally in the same basic themes that I encountered in the books that first drew me to physics as a child, namely nuclear physics and the evolution of the universe, galaxies, and stars. I have been investigating longstanding problems in astrophysics concerning dark matter, dark energy, and the internal structure of collapsed stars that have exhausted their nuclear fuel. I discuss this research in my fifth book, A Universe of Atoms, An Atom in the Universe (Springer, 2002) as well as in the long final chapter of Quantum Superposition (2008).
My research in nuclear physics—in particular, the investigations of different kinds of radioactive decay—made me realise that I needed to learn statistics more deeply than I had before. Although I taught courses on statistical physics, which dealt nearly exclusively with physical systems in equilibrium, the research I was engaged in called for mathematical methods to treat complex time-varying stochastic processes. And so I undertook an intensive self-instruction. As a university student, I became glassy-eyed with boredom at just the mention of the word statistics; this was the one subject I scrupulously avoided, despite having a schedule heavily laden with mathematics, physics, and chemistry courses. But later, as a professional scientist, the subject became much more interesting to me when I perceived it as necessary to my work. The more intensively I studied it, the more applicable I found it to problems outside nuclear physics as well. And the more problems I worked on, the more statistics I needed to learn. Physics and statistics became for me a mutually reinforcing pair of interests. Over time, my initial study of the statistics of nuclear decay branched into a network of diverse explorations embracing not only fundamental physics, but also issues relating to recreation, education, health and medicine, finance, sports, air travel, and other topics. I discuss this aspect of my work in my seventh book, A Certain Uncertainty: Nature’s Random Ways (Cambridge, 2015).
One of my greatest pleasures as a physicist is to recognize a significant conceptual problem, work out the theory of it, and then, whenever possible, go into my laboratory and test it. It is indescribably satisfying to find that the esoteric mathematical symbols created in one’s mind and scribbled on a sheet of paper actually foretell accurately what Nature will do.
There is an individual, personal dimension to the research choices that scientists make. As for me, a physicist who has freely elected to work at an undergraduate college—where teaching takes up most of one’s time, and there are no graduate students or postdoctoral researchers to help with research—I understood from the beginning that a research programme in competition with well-funded, well-staffed scientists at universities or national laboratories would never be successful. However, as I wrote in the last essay of Waves and Grains:
The likelihood of succeeding as a scientist under conditions of severely parceled time and inadequate resources depends critically on the projects one chooses to investigate. It is at this point where a wide-ranging curiosity can mean the difference between a satisfying career and a life of frustration.
Thus, with wide interests, there are wide choices—and I have been a scientist with very wide interests.
In more than a few instances I came to a project serendipitously, having been captivated by a particular unresolved controversy in which different researchers arrived at conflicting conclusions as to whether some phenomenon took place or not, or, if it did, then how. Among the controversies treated in my books are the following consequential issues:
- Amplified reflection – can more light reflect from a surface than is incident upon it? Answer: Yes (Waves and Grains)
- Chiral optics – are two widely used sets of constitutive relations that describe an optically active medium equivalent? Answer: No (Waves and Grains)
- Quantum mechanics – does it conflict with special relativity? Answer: No (Quantum Superposition)
- Nuclear decay – does the disintegration of one radioactive atom influence the subsequent decay of another? Answer: No (A Certain Uncertainty)
- Dark matter – can it comprise very low-mass particles, rather than very high-mass particles? Answer: Conceivably Yes (A Universe of Atoms)
- Dark matter and dark energy – are they somehow related? Answer: Conceivably Yes (A Universe of Atoms)
- Stellar collapse – can a massive star that has exhausted its nuclear fuel collapse to form a hole in space-time where the laws of physics break down? Answer: Almost Certainly No (Quantum Superposition and more recent published papers with colleagues)
The last question above is the question of black holes, a topic that has grasped the attention of news media to such an extent that to much of the public the entire field of physics is reduced to oracular pronouncements by celebrity theorists regarding the collapse and disappearance of matter, leading to a host of paradoxes concerning energy, entropy, information, and travel through space and time. These paradoxes are the product of a mathematical virtuosity unguided by the compass of experimental physics. The problem of collapsed stars is a fascinating one which has by no means received a definitive theoretical treatment. Nevertheless, there are quantum processes that can halt the collapse of a star to create an equilibrium end state of finite size and density.
My career as a physicist has also afforded me the pleasure of numerous close collaborations with colleagues throughout the world. Because of my work as a scientist, my children have grown up as world citizens whose homes have ranged from New Zealand to Finland and throughout the US, Europe, and the Far East. To accommodate this travel, my wife and I undertook the education of our children ourselves, and this homeschooling experience from kindergarten through high school has not only made for close family ties among us, but has also had a profound positive influence on my teaching of university-level science.
If there is one overarching lesson that I have learned from my career as a physicist, it is that the universe is governed by comprehensible physical laws. Nothing supernatural is needed at all to make sense of the world. If only this lesson could be inculcated everywhere myth, superstition, and tradition impede the teaching of science and lead to repression of civil rights.
Trinity's science quad. Left, bottom, and right: Math, Computer Science, and Engineering; Biosciences; and Physics.