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Turn the photos of this passion fl ower and snowfl ake upside down. Do they still look the same?


Symmetry in Snow You can find rotational symmetry in nonliving things, too. Bundle up and go out in the snow. Whirling and twirling snowflakes blow in every direction. It’s a blizzard. T ere’s no order within this chaos. Or is there? Zoom in on an individual snowflake. One


lands on your sleeve. Quick, take a look before it melts. You’ve just seen one of the most beautiful examples of symmetry in nature. To really see a snowflake’s patterns, though, you may need to look at it through a special microscope. A snowflake forms when water vapor


freezes. T e vapor turns into an ice crystal. Its center is a hexagon, with six sides and six points. Six matching branches grow from each point. T e branches have matching ridges and grooves. In some snowflakes, the branches look like feathers. In others, they look like spears or other geometric shapes. You may have to look at a lot of snowflakes


before you fi nd what you’re looking for. Most start out perfectly symmetrical. T en as they fall, they slam into each other. T at can damage these fragile crystals.


Branches break. Snowflakes melt. Just like that, their symmetry vanishes.


Seeing Symmetry From deep in the sea to high in the clouds, symmetry is all around you. Now it’s your turn to find it. Find a caterpillar with bilateral symmetry.


Look for a flower with rotational symmetry. See how many examples you can find. Once you start looking, you’ll see nature’s symmetry all around you.


WORDWISE


bilateral symmetry: when a line can divide an object into matching halves (also called mirror symmetry)


rotational symmetry: when similar parts are arranged around a central point (also called radial symmetry)


symmetry: a matching of parts on each side of a dividing line or around a central point


NOVEMBER-DECEMBER 2012 7


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