A lunar eclipse may not match the magic of an eclipse of the Sun, but it is still one beautiful sight. First of all the circle of the Earth gradually covers up more and more of the Moon, like the Earth does to the Sun in a solar eclipse, then if the conditions are good, the Moon develops a beautiful blood-red hue.
The good news is that it will be possible to see this spectacle in Europe and the U.S. this week, on Wednesday February 20. The total eclipse will be visible from 10:01 to 10:51pm ET (add 5 hours for GMT), with a partial eclipse visible for a couple of hours before and after. (Click here for an excellent guide from Sky & Telescope)
So what exactly is a lunar eclipse, and what’s with the red coloration? Basically, it’s when the Sun, Moon and Earth align in a certain way so that the Earth is directly in the middle of the Moon and Sun. This means that the Earth blocks all the light going from the Sun to the Moon, so the Moon appears dark.
Or at least nearly dark. Some rays of sunlight pass through Earth’s atmosphere and hit the surface of the Moon. These rays are turned red in color, because the light has passed through so much atmosphere – it’s basically the same reason why sunsets are red. This is what gives the Moon that eerie red color only seen during eclipses.
How common are lunar eclipses? There are actually several every year (click here for details of future eclipses until 2100), though a total eclipse usually only happens once every few years. In fact, the next total eclipse won’t occur until 2010, so you’d better make the most of this one!
This graphic from National Geographic (below) sums up nicely everything you want to know about lunar eclipses.