This has been, by far, the most difficult snowflake to include in this year’s series. Partly because of the complex structure, and partly because of the less effective equipment at hand. I hope you’ll all agree that it was worth the effort. View large!
Stellar Dendrite crystals like this have a classic “feel” to them. They are the kind of snowflake you might imagine or see on television. The beauty of natural snow however, is the balanced imperfections across every branch. There are “rules” that snowflakes follow, that define how they grow. The simple physics of freezing water is a wonderful thing to explore when this kind of creation is the result!
The “balance” we see here is all based on a simple and pervasive rule: Whatever sticks out the farthest will grow the fastest. The exposure to new building blocks (water vapour) allows certain parts of a snowflake to grow faster. This simple rule defines the footprint of this crystal. Branches cannot grow farther when the meet another branch, there’s no water vapour there and in most cases you see small gaps between almost-fused branches. They might touch if the conditions are right, but there are very few building blocks in these areas.
It’s a race. Whatever branch or side-branch can grow faster will have the advantage. This extends to plates competing for water as well, as we see in the very center. There is a roughly hexagonal “button” plate in the center, which lost the battle for building blocks against the main branches. Imagine a small column connecting two small plate crystals as this snowflake was an infant. If the wind was blowing against the backside, the rear snowflake would grow and stick out farther. This would effectively choke off most of the growth of the twin plate, giving the features we see in the center.
Snowflakes are complex, yes. There is endless detail in surface contours and cavities within the ice. At the heart of it, they are all based on a few simple rules. The “branching instability” is what I described above. There is also the “knife-edge instability” that makes snowflake grow faster when they are thinner. The angle at which they fall affect how they grow, and electromagnetism plays a role to some degree as well in very specific situations. Air pressure, temperature, humidity, they all work together to create a snowflake. Change any one of these variables and you change the results. Because of the organized chaos of nature, you’re seeing this snowflake.
The universe is beautiful, isn’t it?
To further explore the beauty and physics of snow, and to follow a comprehensive tutorial to photograph your own snowflakes, take a look at Sky Crystals: https://www.skycrystals.ca/book/ - a 304 page hardcover book dedicated to the ideas discussed above. Not only does it make winter more tolerable, it makes you perceive natural beauty with new knowledge and understanding.