(+++) BYWAYS OF A SIMPLE QUESTION

Sky in a Bottle. By Peter Pesic. MIT Press. $24.95.

     This is one of those books that would likely be described the same way by those who enjoy it and those who do not: offbeat, capricious, skewed, quirky.  Those who consider those positive adjectives will enjoy Peter Pesic’s meandering study of blueness.  Those who find the adjectives pejorative had best avoid Sky in a Bottle altogether.

     Pesic’s book has a disarmingly simple starting point: the common childhood question, “Why is the sky blue?”  The scientific answer is straightforward enough: atmospheric particles scatter the redder wavelengths of sunlight less than the bluer wavelengths.  The more-scattered wavelengths are more visible – so we see blue when we look up at a clear sky.  But to Pesic, a physics Ph.D. who is now Tutor and Musician-in-Residence at St. John’s College in Santa Fe, New Mexico, this phenomenon, known as Rayleigh scattering, barely scratches the surface of blueness.  From the opening of his book’s first chapter (“A mystery must emerge before it can be solved”) to an appendix showing how readers can try to duplicate color experiments of times past, Pesic pulls in art and history as well as science in his discussion of celestial blueness.

     In fact, Pesic is less interested in why the sky is blue than in the ramifications of the question “why is the sky blue?” itself.  A given page is as likely to contain a bit of a poem by William Wordsworth; a sketch by the elder Lord Rayleigh (his son also held the title) of his first observations on the blue of the sky; or an illustration from 1815 of Arago’s cyanometer, which allowed light from different areas of the sky to be seen against a color scale.

     Sky in a Bottle switches, sometimes disconcertingly, from plainspokenness to scientific discussion: “Avogadro [a 19th-century natural philosopher] could not determine the number of molecules per one mole because at that time chemistry had no way of counting the individual molecules.  Not knowing that number meant that he did not know the size of one molecule, if the number of molecules in one cubic meter of a liquid or solid equals that volume divided by the volume occupied by a single molecule.  Conversely, determining the size of atoms and molecules would fix the number.”  This sort of writing can be bracing for those of a scientific bent, but it requires a scientist-artist like Pesic himself to switch so often between poetry and analytical mathematics, chemistry and physics.  Indeed, it is hard to escape the suspicion that Pesic essentially wrote this book for himself and perhaps a small coterie of the like-minded.  If you are one of those, you will find Pesic’s musings and his ramblings from science to poesy and back again to be charming; otherwise, you will find them merely discursive.