Snowflakes

Why are snowflakes symmetrical? I really don't know. I have spent a little time researching it and I am frustrated at my lack of ability to find an explanation that is satisfactory.


 Here is a lovely picture of a snowflake. If you notice it has six basically identical slices. Even down to the little bumps and lines. If you look at explanations, like this one, it mentions that the hexagonal shape is due to the structure of water molecules. This makes total sense and is apparent in other places in nature like in minerals. A beautiful example is this Bismuth crystal.



In the Bismuth it is clear that there are some patterns brought on by the molecular structure (it likes going in straight lines and making right angles). However, there is no larger pattern or symmetry.

With the snowflake though each arm of the snowflake not only conforms to the angles dictated by the molecular structure they share additional and unique information (how many branches, how long they are, spacing, etc.).


How is this information passed between all six branches? If all snowflakes were identical I would say it is all based on the molecular structure. But they are not. We know the temperature and humidity affects how each snowflake grows. However, that doesn't explain how six water molecules all align with with rotational symmetry to freeze onto the flake in the same location and at 60 degree angles from each other.

There must be some additional force (input) to cause the exactness of symmetry in conjunction with the vast diversity we see in shapes.

My Hypothesis
I have an idea of how it happens. However, I have not found any reference of this anywhere and I am kind of skeptical of it myself. My idea is that each flake has a local electrical field passing through the center of the flake.




Imagine the flake is lying flat (horizontally) between the green bars above. As the strength of the field shifts it aligns and guides water molecules in specific locations making them merge with the existing flake structure in a guided way. As the temperature, humidity, and field strength fluctuate the snowflake grows increasingly unique but generally symmetrically.

Here is a link to some research being done on electric fields and water ice crystal growth. They don't draw any connections, but it fits with my hypothesis.