A graduate school adviser, Christopher Shera, recently brought to my attention Ray Goldstein’s article “Coffee stains, cell receptors, and time crystals: Lessons from the old literature” (Physics Today, September 2018, page 32). The author, as it happens, was a key undergraduate mentor to me. I recall, during a summer at the Santa Fe Institute, helping Professor Goldstein set up a loudspeaker with a water-filled petri dish on top to produce Faraday instability patterns such as those shown in the article’s figure 3b. Even more remarkable was the article’s figure 1, which reminded me of making a movie of coffee-ring formation for Greg Huber in the summer of 2000. The video aired that evening on the nightly news in connection with a now highly cited paper.1
The main thread of Goldstein’s article—the joy and value of reading “widely”—is important and deserves voicing. The task gets harder daily as the body of scientific literature keeps growing at an extraordinary rate. The article reminded me, an auditory scientist, of a once-forgotten 1948 paper by Thomas Gold that suggested the notion of an “active ear.”2 David Kemp’s discovery of otoacoustic emissions 30 years later3 reignited the idea, and it now lies at the foundation of modern cochlear mechanics. Gold’s paper is acknowledged, cited, and widely celebrated.
My recollection of that paper reminded me of a quote by Werner Heisenberg: “What we observe is not nature in itself but nature exposed to our method of questioning.” Beyond Goldstein’s narrative, I’d suggest that seeing a wider context for the convoluted and technical details of our field is crucial. Making the broad connections helps us enormously.
Consider diffusion, a central heuristic in Goldstein’s narrative. I like to pose simple yet intuitive scientific questions for my students. For example, How does one’s brain work? The short answer is that we don’t really know. The longer and better answer is that we have many of what we believe are essential bits and pieces, such as spiking neurons, excitatory and inhibitory interactions, and network plasticity. And at the core of those are key concepts learned in freshman physics: oscillations, electric potentials, capacitance, and others.
Diffusion, though, is only rarely found in first-year physics materials, yet it is essential to spiking neurons. Electrodiffusion lies at the heart of the Hodgkin–Huxley model, which was laid out in a classic set of papers.4 It also is vital to interneuron communication and plastic changes such as connection weights in Hebbian theory. Although the role of diffusion is central to many of Goldstein’s scientific examples, it is also important in everyday phenomena, which include the sensory and neural processes involved in reading this letter. Incidentally, diffusion can serve as a wonderful pedagogical means to introduce undergraduates to more sophisticated concepts—for example, multivariable functions, differential equations, probability, and bridging micro- and macroscopic domains.
Budding scientists may hear the term “diffusion,” hit that Google Search button, and immediately find themselves at a Wikipedia page. A somewhat useful general resource, it is unlikely to have any clear indications that diffusion is “a process foundational to how your brain works.” No, you need the “serendipitous kind of rediscovery” Goldstein mentions to find such connections yourself. That continual process of renewal is what keeps us going when we hit those inevitable dead ends. And the combination of reading widely and making broad connections is a fruitful form of renewal. (See, for example, Douglas Hofstadter’s 1979 classic Gödel, Escher, Bach: An Eternal Golden Braid.)
