Thursday, January 7, 2010

beginner's guide to appreciating snowflakes

Interesting story in the Chicago Tribune about snowflakes:

Kenneth Libbrecht, [Professor of Physics at CalTech and creator of] has now defined more than 35 different shapes, from radiating plates to capped columns, to bullet rosettes. For snowflake-watchers who don't have a microscope handy, however, here's a beginner's guide to appreciating the snow.

TEMP. (F) 32(degrees) to 25(degrees)

TYPE OF SNOW CRYSTAL = The mash: As temperatures near 32 degrees Fahrenheit there is a greater mix of crystal formationss including plates, columns and dendrites. The structures are more compact, tend to stick together and are perfect for making snowballs and snowmen. "Now you?re getting into your heart attack snow," said CalTech physics professor Kenneth Libbrecht.

TEMP. (F) 25(degrees) to 15(degrees)

TYPE OF SNOW CRYSTAL = Columns and needles: These snowflakes tend to be relatively small and melt easily. "This is kind of forgettable snow," said Libbrecht. "These are kind of the sparrows of the snowflake world. They don't really jump out at you."

TEMP. (F) 15(degrees) to 0(degrees)

TYPE OF SNOW CRYSTAL = Dendrites: The most traditional-looking snowflake -- a stellar dendrite -- forms in higher humidity. It is perfect for skiing, light and fluffy. "These are your standard shopping mall snowflakes," Libbrecht said.

TEMP. (F) Sub-zero

TYPE OF SNOW CRYSTAL = Plates and prisms: Plates and prisms tend to occur at very low temperatures and at low humidity. They make for very dry snow that scintillates in the sun due to the flakes' flat mirrorlike surfaces. Usually the snowfall is so light that no shovels are needed. "This is what I call diamond dust," Libbrecht said. "This stuff just sparkles."

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