The Aurora Borealis is just one of the gifts science and nature give us this winter.

The Aurora

Auroras are caused by the interaction between fast moving particles shot off the sun and molecules in the earth's atmosphere around the magnetic poles. Nitrogen and Oxygen in our atmosphere get "excited" by the influx of energy from incoming charged particles and release photons, creating the light we see in the sky. Because all you need for an aurora are charged particles from the sun, excited molecules, and a magnetic field, other planets also have auroras. This NASA picture shows powerful Earth-sized X-ray auroras on Jupiter!

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All Snowflakes Have 6 Sides

All snowflakes have 6 sides. Water molecules - the building blocks of snowflakes - can only fit together in a certain way. They always form a tiny six-cornered shape, like a hexagonal bathroom tile. And no matter how many water molecules are added, that hexagonal shape remains constant. Nonetheless, that six sided shape can take a wide variety of forms, making nearly every snowflake unique. And the limitations on shape don't mean limitations on size! According to the Guinness World Records, a snowflake 15 inches wide and 8 inches thick was found on on January 28, 1887 in Fort Keogh, Montana.

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Distance to the Sun

The Earth is closest to the sun in the northern hemisphere's winter. Since the seasons are caused by the earth's tilt on its axis and not its distance from the sun, in the United States we experience the coldest temperatures when we are actually closest to the sun. However, being a bit closer to the sun in winter does give us a slight advantage: the earth is moving 1 kilometer per second faster at perihelion which makes our winter 5 days shorter than our summer!

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Polar Bears

The heaviest polar bear recorded was 2,210 lbs. That's huge! But there is more than meets the eye with polar bears. What the naked eye doesn't see:
• their skin is actually black
• they have nearly 4 inches of blubber under their skin to keep them warm
• their thick white fur is not actually white but transparent! Just like snow, a hollow core with air inside reflects the light, making the polar bear appear white and blend in with its surroundings.

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The Poinsettia: A Master of Disguise!

While we usually see the commercialized house-plant form of the poinsettia, in the wild it is a tropical tree native to Mexico that can grow up to 15 feet tall! And those beautiful red "flower petals" actually aren't flowers at all. They are specialized leaves called bracts. The otherwise green leaves turn red because of a seasonal phenomenon called photoperiodism, in which the plant stops producing green chlorophyll because of changes in the relative periods of light and dark the plant is exposed to. Without green chlorophyll, all we see is the red pigment produced for other plant functions. Starting in early September, nurseries replicate and take advantage of this scientific phenomenon by putting poinsettias in complete darkness for 14 hours a day. By the time the holidays roll around they are the perfect shade of red.

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Insects in the Winter

Winter doesn't mean snow for everyone. In Mexico, it isn't snowflakes that fill the air but monarch butterflies completing a 2,500-mile migration. But not all insects can migrate to warmer climes in the winter. Instead, insects in cold climates (who can't produce their own heat) produce glycerol, a sort of anti-freeze, which lowers their freezing temperature and allows their insides to remain viscous!

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