Occurring at 6:38 p.m. ET Tuesday, the 2010 winter solstice marks the official beginning of winter in the Northern Hemisphere. The shortest day of the year boasts the year's longest shadows and fewest daylight hours.

It's all due to the Northern Hemisphere being tilted farther from the sun than at any other point during the year. As a result, the sun follows its lowest arc of the year across the sky. (Get more winter solstice facts.)

In the early morning hours of the winter solstice day, many sky-watchers will see the first shadings of a total lunar eclipse.

The entire lunar eclipse will be best seen from North America and western South America. In most of Europe and Africa, the moon