Lunar Eclipse 2010

(For my blog post "Two Profound Facts about Lunar Eclipses", click here.)

Mark your calendar!

There will be an eclipse of the Moon on the evening of Monday, December 20, 2010 and lasting into the early hours of Tuesday, December 21, 2010. This eclipse is especially well-visible from North America, and a lunar eclipse won't occur again until April 2014. (The last one occurred in August 2007).

This event is best-timed for people living on the West Coast. Here is the schedule (times listed are Pacific):

10:30pm - the Moon begins to enter the Earth's shadow
11:40pm - the Moon is completely covered
1:00am (Tuesday) - the Moon begins to emerge from the center of the shadow
2:00am - the Moon has completely left the Earth's shadow, eclipse over

(If you're in North America but somewhere other than the West Coast, simply adjust for your time zone. For example, in New York City, the eclipse won't start until around 1:30am Tuesday. For Chicago, the eclipse won't start until around 12:30am Tuesday.)

What is a lunar eclipse and why do we see it?

A lunar eclipse occurs when the Full Moon passes into the shadow of the Earth. Since outer space is black, we don't usually see Earth's shadow or even realize that it has one. But it does--for the same reason you have a shadow when you're standing in bright sunlight.

Every couple of years, the Moon's orbit and Earth's orbit line up just right such that the Moon actually goes into the Earth's shadow, which makes it seem as if the Full Moon is disappearing. Here's a diagram:

As a result of this, here is what we see from Earth (see time-lapse video below). As can be seen in the video, notice that oddly, as the Moon approaches the very center of the shadow--where you might expect it to get darkest--it actually begins to turn reddish-brown instead.

In my next post, I'll attempt to explain why that is, and you'll learn two reasons why I think lunar eclipses are so worth checking out: Click here to read it.