Water crystals

Optical microscope photographs of snow crystals.¹ Their characteristic 6-fold symmetry is related to the molecular structure of water, which stabilizes in hexagonal lattices at earth temperature and pressure.² Each crystal has about 10¹⁸ molecules of water, and its very specific shape is due to a complex dependence on temperature and humidity change, and to nonlinear diffusion leading to structural branching instabilities and dendritic patterns. Each snowflake registers a history of interactions with the environment, like “a hyeroglyph sent from the sky”.³

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1. © Kenneth G. Libbrecht (Caltech) [↩]
2. Water has several other possible solid phases, depending on pressure and temperature, with different crystal symmetry. Eg. ice-Ic forming at earth pressure and temperature lower than -80°C has cubic symmetry. [↩]
3. U. Nakaya, “Snow Crystals: Natural and Artificial”, Harvard University Press (1954) [↩]