Why do snowflakes have six sides?
For grown-ups: the science
Snowflakes have six sides because frozen water begins with a six-cornered shape.
Water molecules form a hexagonal crystal lattice when they freeze. Snowflakes usually begin on tiny particles in clouds, then water vapor deposits as ice onto the growing crystal. Temperature and humidity change as a flake travels, making its six arms branch in different ways.
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Transcript
A snowflake is twirling down from a cold cloud. Why does it have six sides?
High in a cold cloud, tiny drops of water freeze around a speck of dust. The frozen water begins in a six-cornered shape.
More water vapor in the air freezes onto each corner. Six arms grow outward from the same little center.
As the snowflake floats through the cloud, its arms can grow different branches. But each arm still follows the first six corners.
So snowflakes have six sides because frozen water starts with six corners. Each snowy arm grows from one of them!