Every so often, more often than you might think, a lunar eclipse happens somewhere in the world. Tonight, there will be a total lunar eclipse visible from the United States and numerous other regions. This can only happen when there is a full moon, but not every full moon results in a lunar eclipse. If the moon is directly along a line drawn from the Sun to the Earth, then the Earth’s shadow falls across the face of the moon, typically giving it a reddish hue. If you aren’t afraid of a little bit of cold weather and weather permits, you might try to see the eclipse yourself.
You can study eclipse phenomena, both solar and lunar, in real-time using this Demonstration.