Why does it seem so quiet right after a snowfall? Why does snow look white when it's made out of ice, which is clear? How does a snowflake's shape tell scientists what conditions are like high above? A lot of questions about snow can be answered only when you look closely at snowflakes.
You may have heard that no two snowflakes are alike. That may be true. Then again, it may not. It's hard to prove, for lots of reasons. For one, since snow eventually melts, every snowflake that has ever fallen isn't around to compare with all the other snowflakes. Who knows if a snowflake that fell in Siberia 300 years ago is the same as one that fell in northern Idaho last week? An estimated 1 undecillion snowflakes (a 1 followed by 36 zeroes) have fallen on the earth. That's a lot of crystals to try to compare with each other.
"Scientists think snowflakes can't be alike because of the way snowflakes are formed," says Michael Split. He's a meteorologist (a scientist who studies weather) at the University of Utah in Salt Lake City. Tiny water droplets in the cold air high in the clouds freeze into ice crystals. More molecules of water attach to each crystal. The crystals may fall through different layers of air at different temperatures. They are banged about by winds. Some layers of air have more moisture than others, so crystals may join together.
By the time an average snowflake falls to earth, it may contain billions of molecules of ice. These molecules can join together in so many different ways, that the number of possible combinations is enormous. Big enough to make it very unlikely that two snowflakes would form exactly alike. But it's not impossible.
"To the human eye, two snowflakes may look very much alike," Mr. Split says. "But looking closer, through a magnifying glass or microscope, you would probably see many differences between them."
One researcher who learned a lot about the differences between these ice crystals was the Snowflake Man. His real name was Wilson Alwyn Bentley. He lived in Jericho, Vt., and spent 47 years observing and writing about snowflakes. He took his first photomicrograph of a snowflake on Jan. 15, 1885. He was 19.
Over his lifetime, he made about 6,000 more snowflake photos.
By the time a book of Mr. Bentley's photographs was published in 1931, he was known as the Snowflake Man. His book, "Snow Crystals," is still available today. It contains almost 2,500 photos of ice crystals, some of which are reproduced here. (You can see more snowflake photos at this Web site: www.snowflakebentley.com)
Scientists today study how a single ice crystal forms and how the small crystals join into larger snowflakes. They also look at how the snowflakes stick together. You may have noticed that everything seems quiet after a snowstorm. That isn't just because everyone is staying inside where it's warm. Newly fallen snow isn't packed down yet. The snowflakes stack lightly against each other with a lot of space in between.
This arrangement absorbs sound waves. Things really are quieter.
As the snow settles, the quiet disappears. Snow with a hard, smooth surface reflects sound waves. Sounds seem clearer and carry farther.
Scientists aren't the only ones who are concerned about snow conditions. Light, "dry" snow, called "powder," doesn't stick together well.
Skiers love it because it doesn't stick to their skis and slow them down. It's also very soft if you fall down in it. But you can't make a good snowball with powder snow. Wetter snow sticks together better and makes much better snowballs and snowmen. That's important to snow sculptors. At competitions around the world, people create castles, people, animals, dragons, and other amazing shapes out of snow.
They combine artistry and science to form the snow into the images they want and to keep it in place. At least long enough for the judges to take a good look.
But no matter how impressive a snow sculpture may be, the most fascinating and beautiful part of it may be the tiny snowflakes that form it.
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