What Gives a Snowflake Its Intricate Shape

Why do snowflakes have 6 arms? What causes the symmetry? Why are snowflakes unique?

How Are Snowflakes Formed

Snowflake’s journey begins when water vapor in the air freezes onto a tiny dust particle. As a result, a small ice crystal is formed. As it falls down, more water vapor freezes onto it and the crystal grows up to a snowflake with six arms.

Why Six Arms

The way a water molecule is structured, (one hydrogen + two oxygens) causes them to freeze into a hexagonal structure. As a result, the snowflake ends up having six arms:

There is actually nothing magical in this hexagonal structure. It emerges naturally since being in a hexagonal structure is physically the most optimal/efficient way for the water molecules to align themselves when freezing.

The Overall Shape of the Snowflake

A snowflake always has six arms due to water freezing into a hexagonal structure. However, the way the arms look varies a lot among each snowflake.

The atmospheric conditions affect how snowflakes get their final form. Especially, the temperature and humidity are key factors on the way of how falling ice crystals grow up.

E.g. in warmer conditions, the crystals are more needle-like whereas in colder conditions they tend to be flat and more plate-like. As a result, different-looking snowflakes are produced.

Why No Two Snowflakes Are Identical

As you already know, the shape of the snowflake depends on the atmospheric conditions that the ice crystal experiences as it falls down.

The fact that there are no identical snowflakes originates from the fact that the atmospheric conditions vary depending on the path a snowflake takes.

But how can two snowflakes from the same cloud experience different atmospheric conditions by taking a different route?