If you're reading this on 14 April 2014, you're just in time! Tonight, as long as you live in North America, you can catch a total lunar eclipse from just about anywhere. While not exceptionally rare, total lunar eclipses are pretty special events and definitely worth staying up for - if it's not cloudy, that is!
What is a lunar eclipse? It's actually pretty straightforward. Eclipses occur because of the arrangement of the Sun, Earth, and Moon. Think of the Sun as a giant flashlight shining brightly on the Earth. Like anything with a light pointed at it, the Earth casts a shadow. When the Moon passes into this shadow, an eclipse occurs. Not too tricky, right? Of course, we can always add in additional complications. We call this a total lunar eclipse because the Moon will pass entirely into the darker, center region of the shadow. This area is called the umbra. Farther out, the Earth casts a fuzzier, not-so-dark shadow called the penumbra.
If you're still with me, a couple of questions may have sprung to mind by now. For one, why doesn't this happen every month? Actually, if the Earth and Moon always orbited in the same plane, an eclipse would happen every month at the full Moon. In reality, though, the Moon's orbit is a bit tilted when compared to that of the Earth. This means that during a full Moon, the Moon is usually above or below the Earth's shadow, not in it. Too bad!
So will the Moon disappear entirely? Not quite. Although the Earth will block the straight-line path of the Sun's light within its shadow, light actually bends when traveling through the Earth's atmosphere, an effect called diffraction. Diffraction is dependent on the color of the light, though, and it turns out that mainly red light makes it through to shine on the Moon This results in the dark red Moon you can see in the above picture.
The nice thing about lunar eclipses is how easy they are to observe. Unlike a solar eclipse, which lasts only a few minutes, lunar eclipses last for hours. Lunar eclipses are also safe to view without any special equipment. Just go out and use your eyes! Remember: never look directly at the Sun without the aid of special equipment.
When should you look? The total phase of the eclipse begins around 3:00 AM EDT and lasts for an hour and twelve minutes. If that's a bit too late, you can still catch the Moon entering the penumbra starting around midnight. The following list, courtesy of NASA, lists the major events of this eclipse. All times are in Eastern Daylight Time (EDT):
12:54 AM - Moon enters penumbra
1:58 AM - Moon enters umbra
3:06 AM - Total eclipse begins
4:24 AM - Total eclipse ends
5:33 AM - Moon exits umbra
6:38 AM - Moon exits penumbra
For more technical details, visit the NASA eclipse page here.