When the air turns crisp and snow begins to fall, there’s something magical about taking time to watch those delicate flakes drift gently from the sky. But there is also a fascinating blend of geometry and physics working together in the chill of the winter air.
Snowflakes are one of nature’s most stunning examples of symmetry and geometric design, and every single one tells a unique story.
The geometry of ice crystals
Simply put, a snowflake is just frozen water, but its shape is far from simple. Snowflakes form when water vapour in the atmosphere freezes and creates tiny ice crystals that grow outward from a central point. This freezing occurs either when the surrounding air is extremely cold(–35°C or below), or in warmer clouds, where the vapour can cling around a dust or pollen particle.
When water freezes, its molecules naturally arrange themselves into a hexagonal pattern. This happens because each water molecule—made of one oxygen atom and two hydrogen atoms—bonds at angles that favour a six-sided structure. As a result, every snowflake grows with six arms (or spokes) extending from a central point, like a perfectly balanced wheel.
Symmetry in a flurry
If you look closely at a snowflake under a microscope, you’ll notice that each arm of the snowflake is slightly different. As a snowflake falls through the atmosphere, it passes through layers of air with different temperatures and humidity levels. While all six arms experience the same conditions at the same time, tiny variations in the environment cause the arms to grow in similar, but not perfectly identical, ways.
Think of it like decorating a snowflake shaped Christmas cookie. You might use the same technique on each side, but tiny differences in pressure, angle, or movement lead to subtle variations. While the molecular structure of a snowflake favours symmetry, the environment introduces tiny imperfections that make each one unique.
This delicate balance between order and randomness is what makes snowflakes so captivating. They’re symmetrical enough to look organised, yet variable such that no two spokes are ever quite the same.
Why no two snowflakes are alike
You’ve probably heard that “no two snowflakes are alike”. This isn’t just poetic — it’s scientifically true (or at least, extremely likely). A single snowflake’s journey from cloud to ground is full of twists and turns. Minute changes in air temperature, humidity, and wind speed alter how the ice crystal grows.
At higher humidity, branches sprout faster while at colder temperatures, the patterns become sharper and more intricate. Even a change of one degree Celsius can transform a simple hexagonal plate into a stellar dendrite.
While quintillions of snowflakes form every year, each one travels through a slightly different atmospheric path. This means that the chances of forming the same pattern twice are astronomically small. In fact, it’s been estimated that the number of possible snowflake shapes may exceed the number of atoms in the universe!
So, as you watch the snowflakes fall this winter, remember that each one is a tiny masterpiece of geometry and physics and a frozen record of the environment it just passed through.
Festive quiz
Last quiz solution
a) Candela (Ca)
Your next seasonal question
In this article two different snowflake shapes were mentioned, hexagonal plates and stellar dendrites. Which of the following is also a snowflake shape?
a) Column
b) Stack
c) Tube
Read the next article to find out!
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