On the night of March 23rd, while many of us are celebrating spring, the moon will be putting on a show of its own. Around 10 P EST, the moon will begin to undergo a partial eclipse.

      A lunar eclipse occurs when the moon is full and it passes through the shadow of the Earth. The moon does not shine by its own light, but by reflected sunlight. So as the moon passes into the shadow we see it darken and nearly disappear.

       Earth's shadow has two parts, the umbra and penumbra. The umbra is the region of total shadow, if we were within this portion of the Earth's shadow, we could not see the Sun at all. The penumbra is the region of partial shadow, if we were in the penumbra, we would see part of the Sun peeking around the edge of the Earth. A good demonstration of this is to stand outside on a sunny day and hold your hand out at eye level over smooth ground. You will see that your hand's shadow has both an umbra and penumbra. The higher you hold your hand, the more obvious the penumbra will become.

 
    It takes the moon several hours to pass completely through the umbra. Partial eclipses are of less duration. During this time the moon begins to dim and turn a copper-red because the only sunlight reaching it is sunlight passing through Earth's atmosphere.

      It is somewhat of an eerie sight to see the moon dim like this. We know what is happening, our ancestors did not, and it sometimes frightened them badly! In fact, the word "eclipse" comes from the Greek word ekleipsis, which means abandonment. Our ancestors feared that their world had gone awry. They feared these unpredictable menacing events they were sure brought evil.

      We know now that we can predict eclipses with great accuracy. We know that the moon has a cycle of 18.6 years. You might wonder why we do not have a lunar eclipse every month.

      Just as the Earth's axis is tilted 23.5 degrees, the moon is also tilted 5 degrees on its axis. This makes the moon's path go above and below the plane of the Sun ( the ecliptic plane). So the moon is not exactly the same place each month as it moves behind the Earth. When the moon's path takes it directly over the ecliptic plane, we experience a total lunar eclipse. If the moon's path takes it very close to the ecliptic, we have a partial eclipse.

     This eclipse is a partial eclipse, but it moves so deeply into the shadow that only a thin crescent will remain unblemished. Look for it to begin late into the evening. At 9:58 the moon's edge begins to move into the Earth's penumbra. The shadowed part of the moon should take on a deep copper-red color.

    Mid-eclipse occurs at 11:29PM EST. It is during this phase that there will only be a sliver of the moon that remains outside of the shadow. An added attraction of this eclipse is that the red planet Mars is only 10 degrees away (two fists at arm's length) from the moon.

     The moon escapes the Earth's shadow around 1:21 AM, and around then, if you look to the north, you just might find comet Hale-Bopp has peaked into view!