Snowflakes are one of the most recognizable and
endearing symbols of winter. Their intricate shapes have been the
inspiration for Christmas ornaments, jewelry and U.S. postage stamps.
They are the subject of song, school projects and even scientific
investigation, including a possible impact on global warming.
Jon Nelson, a researcher with Ritsumeikan
University in Japan, has studied snowflakes for 15 years, and has some
interesting insights into their delicate structures.
Is it true that no two snowflakes are alike?
The old adage that ‘no two snowflakes are alike'
may ring true for larger snowflakes, but it might not hold true for
smaller, simpler crystals that fall before they've had a chance to
fully develop. Regardless, snow crystals have tremendous diversity,
partly due to their very high sensitivity to tiny temperature changes
as they fall through the clouds.
How do snowflakes form?
A snowflake starts as a dust grain floating in a
cloud. Water vapor in the air sticks to the dust grain and the
resulting droplet turns directly into ice. And that's where the
science kicks in.
First, the tiny ice crystal becomes hexagonal (six-sided).
This shape originates from the chemistry of the water molecule, which
consists of two hydrogen atoms bonded to an oxygen atom. Because of
the angle of the water molecule and its hydrogen-bonding, the water
molecules in a snowflake chemically bond to each other to form the
six-sided flake. The flake eventually sprouts six tiny branches. Each
of these branches grows to form side branches in a direction and shape
that are influenced by the clustering of water molecules on the ice
crystal surfaces.
Why are scientists interested in the study of
snowflakes?
The study of snowflakes, which are really ice
crystals, has recently become important due to the possible influences
that these crystals have on global climate change. Researchers now
believe that ice crystals play a crucial role in ozone depletion,
possibly by acting as a catalyst to break down ozone. Ice crystals in
the atmosphere also play a key role in building up electric charges in
clouds and are therefore believed to influence the production of
lightning, although the mechanism is unclear.
Source / Further
information:
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Publishing date: 13-Dec-2006
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CLICK HERE to view illustration about how snowflakes are
formed
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The American Chemical Society's "WonderNet"
Web site has a step-by-step hands-on activity for children to make
their own snowflakes.
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Jon Nelson has written several research papers
on snowflakes, including one in the American Chemical Society
journal, "Crystal Growth & Design." That paper, published in 2005,
helped explain several previously unanswered phenomena about
snowflakes:
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