With all the trillions of snowflakes that are piled up in your driveway, coating the mountain tops, and plowed from the road, it’s probably true that no two snowflakes are alike. Proving this would be quite a feat, for obvious reasons, but you’ll as you read below, you’ll see why the old adage it probably true.
Snowflakes are very sensitive to micro-environmental variables such as wind, temperature, humidity, air pressure, cloud condensing nuclei, and air particles. Add an element of chaos theory to the mix and you’ll see below that there are numerous factors which affect snowflake growth.
When temperatures are between 27°F and 32°F (-2.8°C and 0°C), only a 6 degree variation, tiny snow crystals take the form of six-sided plates. When the temperature falls below 27°F, needles form. When it gets just a few degrees colder, hollow columns start to form. And when it gets even colder, fern-like stars form. Once it gets even colder, the whole cycle repeats itself with six-sided plates, columns, needles and fern-like structures reforming.
Different humidity levels also affect how the flakes grow. When the humidity is low, snow crystal growth occurs on flat surfaces. When the humidity is higher, snow crystal growth occurs along edges, corners and extremities.
Snow crystals need something to form on, such as a dust particle, debris or cloud condensing nuclei. Just like a raindrop, snowflakes don’t simply form out of “nothing”. Once water molecules start to freeze onto the the particles surface, the beautiful shape of the snowflake starts to form, and it’s growth accelerates as the snowflake gets bigger in size.
Photograph Source: National Geographic
During its formation, the snowflake might bump into another snowflake which can cause it to deform rapidly grow in a different direction. By the time the snowflake reaches the ground, it may have taken an hour or more to get there due to wind currents and the terminal velocity at which a snowflake falls.
If the sun is shining, even just a little bit, it too can affect the snowflake’s shape. As the sun heats the ground or becomes obstructed by clouds, minute temperature variations occur at various elevations. These are enough to either slow growth, or change the overall shape of the snowflake. And because the wind mixes the air of varying temperatures, all sorts of chaos ensues during the growth period.
And these are just the known causes of snowflake formation. Scientists openly admit that there are probably many other factors at play and the old adage that ‘no two snowflakes are alike’ is nearly impossible to prove.
However, the faster the snowflakes fall to the ground and the more homogeneous the environment, the less time there is for the environmental factors to affect their shape. The odds of finding two snowflakes that are very similar or perhaps even the same, is more likely.
However, when you bring a powerful microscope into play, the odds are astronomically against such a feat. That’s because there are an estimated 10,000,000,000,000,000,000 water molecules in a typical snowflake. For all those molecules to arrange themselves in the same exact shape twice is very unlikely, indeed! However, considering the number of snowflakes that have fallen to the ground since the beginning of time is something like 10 followed by 34 zeros, the odds are starting to look a little better the perhaps two snowflakes are alike, but we’ll never know.