There is a familiar feeling to those for whom winter is a special season—the tingle one feels on seeing the first flakes of snow drift from the sky or upon drawing open the curtains to find the first snowy morning. Fresh snow brings brightness and new activities following late fall's muddy ground and dreary light. Even when we are no longer young, many of us still tilt our heads skyward and chase falling snow in an attempt to catch the perfect flake on our tongues. When we tire, we may look down at our sleeves or the back of our gloved hands and realize we already have that perfect flake amongst a cornucopia of crystals that fell from the sky and landed perfectly preserved for a moment in time.
Kenneth Libbrecht is clearly one for whom snowflakes remain hypnotic, and he has shared this fascination through nine previous books featuring photographs of snowflakes. If you've seen a photograph of a snowflake, chances are it was taken by Libbrecht. The beauty of snowflakes inspires scientific wonder, and his images serve to share this wonder with a wider audience.
Now Professor Libbrecht adds a somewhat more scientific monograph to his visual snowflake morphology library: Snow Crystals: A Case Study in Spontaneous Structure Formation. The book is the newest in a long series of treatises, perhaps in modern scientific times originating with Johannes Kepler's 1611 “Strena, seu de Nive Sexangula” (On the snowflake, or the six-angled crystal), wherein emergent patterns form the basis for fundamental exploration. Libbrecht's contribution is printed in the format of a textbook, and it appears to have the ambition to cover snow crystals as comprehensively as possible. Given that monographs like Hobbs's 1974 Ice Physics, Pruppacher and Klett's Microphysics of Clouds and Precipitation, and Petrenko's Physics of Ice are several decades old, there is certainly room for an updated reference text.
Libbrecht begins the task with some general descriptions of snowflake phenomenology, which provides context for a short historical account of how many eminent scientists have been inspired by the beauty and uniqueness of the crystals. From Chinese philosophers to Descartes and Kepler, the symmetry, clarity, and diversity of crystals have inspired many thinkers. In fact, attempts to explain their symmetry led to the development of proto-atomistic theories, proposing that the crystals consisted of fundamental building blocks.
The obstacle that Libbrecht faces is that the striking appearance of snow crystals is only the tip of the proverbial iceberg one can explore in the context of ice. On the one hand, ice is unusual among polycrystalline solids in having both liquid and gas forms at temperatures easily accessible in the lab, enabling studies, for example, of the effect of surface disorder on bulk melting. This range of accessible forms makes defining the bounds of icy problems quite a difficult task. On the other hand, the uniqueness of ice, or rather H2O, is its essential role in our environment and lives. The phenomenon that Libbrecht clearly wants to explore is the emergence of visual structures from frozen water molecules. Fundamentally, this is a manifestation of non-equilibrium growth, where the equally stimulating questions related to, for example, how the initial seed forms (nucleation), or what is the surface state (disordered, quasi-liquid, premelted), are of secondary importance when there already exists the driving force for growth.
Libbrecht is most successful when he provides glimpses of the plentiful underlying physics but quickly moves on to the phenomenological. He appears to recognize this and by the halfway mark the text refocuses on creating and cataloging all manner of snow crystals. From creating crystals in the laboratory to observing and imaging fallen snow, the text becomes a handbook for a modern-day Wilson Bentley.
I have spent a good deal of time reflecting on where this book fits into a physicist's library—especially in the age of digitized media. At its heart it is not a textbook, or at least not one I could imagine utilizing in any course beyond a specialized seminar. However, Libbrecht's images are wonderful and best viewed on paper, and the book's high quality paper stock and printing make them stand out. This is a book that is fun to return to for the pictures, the technical descriptions—and simply for the wonder. It is well-suited to the scientifically curious, analog generation, and a worthwhile addition to Libbrecht's multitude of more purely artistic contributions.
Erik S. Thomson is a Senior Lecturer in Experimental Atmospheric Chemistry at the Department of Chemistry and Molecular Biology, at the University of Gothenburg in Gothenburg, Sweden. Erik's research focuses on phase transition behavior in the atmosphere and other aspects of physics and chemistry at interfaces—with a keen eye towards icy surfaces.