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san francisco is hexagonally aware
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Book Lesson:  Visions of Symmetry by Doris Schattschneider
Chapter 3, page 106 - 107

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some hexagons at a place i was at..... yep...
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Snowflake-a-Day #54
Tiny hexagonal plate-life snowflakes are anything but boring. Even crystals without much surface detail will have intricate patterns inside them! As luck would have it, these patterns can also create some lovely and unexpected colours. View large!
 
This snowflake is on the tiny end of the scale. Yesterday’s snowflake measured 7.6mm, and this one is much less than 1mm in diameter. Too small to even notice with our own eyes, and it’s also pushing up against the physical limits of light to make this photograph. At these extreme magnifications, diffraction causes light that is supposed to hit one pixel to spread out over a larger area of the camera sensor, effectively blurring the results. Greater magnification doesn’t always mean greater resolution and details!
 
The colour here is more vibrant than most, resembling a melted puddle of rainbow sherbet. These colours are natural, and caused by thin film interference between layers of ice and air inside the snowflake. Tiny bubbles often form inside snowflakes and if these bubbles are just the right thickness, we can see light interacting with itself. Here’s the pages of Sky Crystals that give a full explanation of the magic: http://skycrystals.ca/pages/optical-interference-pages.jpg
 
It’s not often that the proper conditions exist to see these colours. So far this year, only one snowfall creates these kinds of crystals in abundance. While I hope for more, it’s completely unpredictable when that might happen.
 
This particular snowflake has something odd about it. The colours form when the bubbles are the right thickness, and you can see the boundaries to that around the edges of the crystal (and multiple-order interference patterns faintly seen in other areas). But right near the center, there is a ring of features that look like bubbles, but there already seems to be bubbles formed underneath. It could be that, when one bubble is forming, the edge of the ice can produce an additional cavity and form layered bubbles, but this is not something I have ever seen before. These features could also be indentations in the surface of the ice, but their brightness seems to show another reflective surface (indicating a bubble).
 
There is an entire section of the book Sky Crystals dedicated to the colour found inside these tiny snowflakes. If you want to know the science of how these beauties form or the special photographic techniques to capture them, give it a read! http://www.skycrystals.ca/ - at 304 pages, it’s got everything you wanted to know about the subject and then some. :)
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