Étienne Ghys is a mathematician, permanent secretary of the French Académie des sciences, and a member of the Conseil scientifique de l’Éducation nationale. He is head of research at the CNRS, in the department of pure and applied mathematics. He is known for his research in geometry and on dynamic systems, as well as for his books written for the general public.
It’s not surprising that the geometrician Etienne Ghys is fascinated by snow: a snowflake is a marvel of geometry and symmetry – capable of enthralling and inspiring the young minds to whom this very short but abundantly illustrated book is addressed. But adults will also find the same wonderment in it.
By following the history of the scientific observation of snow, we meet some colorful characters: the Swede Olaus Magnus, France’s own Descartes, the Englishman Robert Hooke, the Dutch Martinet, the American Scoresby, the Lady Cecilia Glaisher, and the Japanese Ukichiro Nakaya, before the molecular explanation is set forth by the Nobel Laureates William Bragg and Linus Pauling: the shape of snow crystals is connected to the temperature and the humidity of the places where they are formed, which, by observing a snowflake under a magnifying glass, enables the viewer to know the conditions of the surrounding atmosphere.
The final stage of this stroll in the snow is more physical (from crystals to “quasicrystals”) and mathematical: is it possible for a computer to reconstruct the shape of all existing crystals? Not only have Norman Packard and Clifford Reiter succeeded in doing this, but in passing they have demonstrated a few essential theorems.
The author’s skill is in delivering a work of science without ever giving the reader the impression that he is drowning in a laborious text of scientific pedagogy: the tone is that of a story-teller, warm, not at all intimidating, who carries the reader along…