Every Snowflake Has Six Arms

The beautiful, six-pointed shape of a snowflake is a direct result of the chemistry of water. When water vapor freezes into ice high in the atmosphere, its V-shaped molecules link together through hydrogen bonds. The specific angle of these bonds naturally forces the molecules to arrange themselves into a stable, repeating hexagonal lattice. This microscopic hexagonal structure is the fundamental blueprint that dictates the larger, six-fold symmetry we can see, a phenomenon first pondered by astronomer Johannes Kepler in the 17th century.

As this initial ice crystal, a tiny hexagonal prism, falls through the clouds, its journey shapes its final design. The six corners of the prism are more exposed to the surrounding water vapor, causing them to grow faster than the flat faces and form the classic arms, or dendrites. The snowflake's intricate pattern becomes a detailed record of its path; minute fluctuations in temperature and humidity dictate whether the arms grow long and thin, short and broad, or form other complex features. Because each arm experiences nearly identical conditions at the same moment, they grow in beautiful synchrony, creating the symmetrical marvels that fall to the ground.