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The Optics of Life: A Biologist's Guide to Light in Nature

Optics (a physical science) and Biology (a natural science) have been brushing up against each other to such a great extent that visual ecology and physiology have become significantly productive subdisciplines in biology. Unfortunately much of the physical principles that govern optical phenomena have been burdened with arcane units and language that prevent interested biologists from having a more complete understanding. Thankfully, Sönke Johnsen serves as a conduit between these two fields, as he gracefully presents the physical principles of optics in a simplifying manner that makes the reader want to apply new found knowledge to their own research. As Dr Johnsen states in the introduction, ‘‘This is not a book about visual ecology.’’ Instead, it is a book that describes and explains some of the more important physical phenomena that govern how various animals make use of light. So much about this book is excellent—even the cover is good eye candy: it shows partially transparent and partially iridescent Tetrorchis jellyfish swimming in a dark black environment. The color being reflected by the animal in this photograph is a result of transparency, pigment spectral absorption, and iridescence caused by coherent scattering. This is an apt description of the book’s subject matter because it perfectly illustrates how animals take advantage of their light environment to generate the myriad of colors found in nature. The book contains 10 chapters as well as 7 appendices. The chapter topics are intended to provide biologists with ‘‘90% of what is necessary to know in order to study optical related issues in biology.’’ As such, it is written simply and clearly and should serve as a do-it-yourself physics course specially written for scientists who study light (e.g., optical scientists, opticians, physiologists, and ecologists). The chapter topics range from a discussion about units and geometry, emission, absorption, scattering, and interference, to chapters about fluorescence, polarization, and measuring light. The book contains over a hundred black and white illustrations and images that aid his explanations immensely. There is also an eight-page section of glossy colored photographs showing spectacular images of a wide variety of optical and bioluminescent phenomena. The book ends with a chapter that is a sophisticated treatment of the physics underlying light and is intended to provide the reader with an appreciation for the complexities of studying it. This book is written in an entertaining style so it is a pleasure to read. Each chapter starts with a thought-provoking quote, and ends with an amusing and interesting anecdote or reverie. My favorite chapters contain illuminating discussions on scattering, scattering with interference, absorbance, and transparency. I have only one criticism about the book, and I am not sure it is even one that can be addressed by the author. I felt the placement of the chapter on units and geometry (i.e., Chapter 2) was problematic: This chapter was specifically written to clarify confusing terminology, and Sönke Johnsen does an exemplary job, but its placement requires one to read this before the really interesting phenomena are presented. The only drawback of this chapter’s current location is that its placement might steer away impatient individuals. Finally, I have one or two suggestions for the second edition: I believe a neat addition to this already great book would be to include a chapter on optics in which the author discusses the biology of some of the stranger examples of animal signals, vision, etc., and I believe an appropriate quote for such a chapter would be ‘‘Once in awhile you can get shown the light in the strangest of places if you look at it right’’ (Robert Hunter, from ‘‘Scarlet Begonias’’ by the Grateful Dead).