Snow is precipitation in the form of flakes of crystalline
water
ice that falls from clouds. Since snow is composed of small ice
particles, it is a granular material. It has an open and therefore soft, white, and
fluffy structure, unless subjected to external pressure. A snowflake is either a single ice crystal or an aggregation of ice crystals which falls
through the Earth's atmosphere. Snowflakes come in a variety of sizes and
shapes. Complex shapes emerge as the flake moves through differing temperature
and humidity regimes, such that individual snowflakes are nearly unique in
structure. Snowflakes encapsulated in rime form balls known as graupel. Snowflakes appear white in color despite being made of clear ice. This
is due to diffuse reflection of the whole spectrum of light by the small crystal facets. A snowflake consists of roughly water
molecules, which are added to its core at different rates and in different
patterns. As a result, it is extremely difficult to encounter two identical
snowflakes. Initial attempts to find identical snowflakes by photographing thousands their images under a microscope from 1885 onward by Wilson Alwyn Bentley found the wide variety of snowflakes we know
about today. The process of precipitating snow is called snowfall. Types
that fall in the form of a ball due to melting and refreezing, rather than a
flake, are known as hail, ice pellets or snow grains.
