Why do snowflakes have six sides?
For grown-ups: the science
Freezing water molecules make a tiny crystal with six corners, and the snowflake grows outward from them.
Snowflakes form when water vapor deposits as ice on a tiny nucleus in a cold cloud. Hydrogen bonds between water molecules favor a hexagonal crystal lattice; growth outward from this hexagonal core produces six-fold symmetry, though branching patterns vary with changing cloud temperature and humidity.
What about...?
Ask your child's own question
Transcript
A tiny snowflake is drifting past your window. How does it grow six points?
High in a cold cloud, water vapor freezes into a tiny ice crystal. Its water molecules link at angles that make six corners.
More water vapor freezes onto the six corners. Each corner grows outward, so the crystal keeps its six-part shape.
The arms can grow fancy branches in the cloud. But they all begin with the same six-corner pattern.
So snowflakes have six sides because freezing water builds a six-corner crystal pattern.