Tuesday, August 21, 2012

The Stellar World of Snow Flakes

I saw this on 22 words This was suggested to me by a loyal reader (me) and I thought it was an excellent idea for a post.

Snow flakes come in many forms but the most recognizable are the star shapes and experts call those dendrites because they have to use fancier words than the rest of us or their student loans will have been for naught. Yes, naught!

Researchers at Beltsville Agricultural Research Center have been using an electron microscope designed for very low temperatures, where the phrase very low temperature is a relative term because I've walked to my car in very low temperatures and that was nowhere near as low as this microscope goes, to capture all kinds of snow particles. These are some of the pretty ones.

Hexagonal snow crystal with offset branches is pretty!

Ordinary hexagonal dendrite

In snow classification, a dendrite is a class of snowflakes that has 6 points, making it somewhat star shaped or the classic - dare I say quintessential - snowflake shape. 

You may have heard the story that Eskimos have many words to identify specific types of snow. This legend is problematic - exactly what defines an Eskimo? - and wrong. The language of the Innuit people describes snow in about the same amount of words as English does. However there are many different varieties of snow and these pictures show why that is the case.

Stellar snow crystal

Hexagonal plate with dendritic extensions

Different conditions form different types of snow. Also, once the snow flake has landed, conditions will dictate how well it keeps its form.

Snow after several days in snowpack exhibiting rounding and if I'm not mistaken, 
two little beady eyes as well

A common hexagonal plate snow crystal

This looks like another hexagonal plate with dendrite extensions.
Look at me classifying snowflakes!

Sampled shortly after landing

You might think this is another dendrite but it's really 
Atlantis from Stargate: Atlantis. I kid!

Depth hoar crystal

Sometimes a snow crystal passes through a cloud with supercooled water droplets, the kind that CANNA CHANGE THE LAWS OF PHYSICS! Or that can exist in an unfrozen state down to temperatures of -40C. When the snow comes into contact with this very cold water it freezes onto the surface and changes the shape of the snow flake. This process of crystal growth is called accretion.

When an ice crystal has frozen droplets on it, it is called a rime. The particles that form in frozen fog are rimed crystals. 

If this process accumulates to the point of changing the shape of the original snow crystal, the resulting crystal is called a graupel, which is soft hail or snow pellets.

Rimed plate crystal

Rimed dendrite

Rimed column crystal



And these are man made snow blobs in all their glory. *slow clap*
Well played Mother Nature.

This is the Low Temperature (HAH!) Scanning Electron Microscope
Or the LT-SEM as they call it.

Copper plates are used to catch the flakes and are coated on one side with methyl cellulose - a gel like solution. As far as I can figure out, this plate is then immersed in liquid nitrogen. So the words "low temperature" Scanning Electron Microscope seems to be an understatement. Cold Enough To Freeze the Balls Off a Brass Monkey Scanning Electron Microscope would be more accurate if we could agree on what exactly a brass monkey was. Anyway the acronym - CETFTBOABMSEM - is a tad clumsy. I know what you're thinking and you're wrong.  ADCOMSUBORDCOMPHIBSPAC is the longest English acronym in the world. It's a navy term which stands for Administrative Command, Amphibious Forces, Pacific Fleet Subordinate Command. I guess ACAFPFSC was too pedestrian. Damn my digressions!!!

If you want to check out more snowflake classifications this was an interesting site. It had pictures with the classifications. I like pictures.

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