Early in the morning of Dec. 21 here in the Ohio Valley, we will witness one of the most spectacular nighttime sky events, a total eclipse of the Moon, often called a total lunar eclipse. There are two kinds of total eclipses we normally think about. A solar eclipse occurs during the daytime when the Sun, Moon and Earth line up. The shadow of the Moon falls on the Earth blocking out light from the Sun. The Moon phase is always a new Moon during a solar eclipse. A total solar eclipse is limited to narrow areas on the Earth from where the Moon casts a small shadow.
Lunar eclipses happen when the Sun, Earth and Moon are in a line and the shadow of the Earth falls on the Moon. The Moon phase is always a full Moon during a lunar eclipse. Lunar eclipses are seen by skywatchers over half the world, or by anyone that can see the Moon during the lunar eclipse.
Another difference between a solar and lunar eclipse is how you watch it. To watch a solar eclipse you need special filters to block the Sun's bright and eye-damaging light. Without taking the precaution of using special filters to watch a solar eclipse, your eyes could be permanently damaged. A lunar eclipse is completely safe to watch and requires no special equipment.
Lunar eclipses come in two varieties. The first is called a "partial eclipse" where only part of the Moon is covered by the shadow of the Earth. The second variety is more spectacular and happens when the entire Moon that we see from the Earth is totally covered by the Earth's shadow. We call this kind of lunar eclipse a "total lunar eclipse"
The last total lunar eclipse for us here in North America was in February 2008.
A total lunar eclipse has multiple stages. The very beginning and very end stages of a lunar eclipse are difficult to see; the changes are slow with small changes minute to minute. The lunar eclipse will begin at 1:33 a.m. This is when the Moon first contacts the Earth's shadow. A slight dimming on the east side of the Moon will be seen. The Moon slowly will enter the Earth's shadow. The Moon will be totally within the Earth's shadow at 2:41 a.m. and will stay in the total shadow of the Earth until 3:53 a.m.. At 3:53 a.m., the eastern side of the Moon will slowly brighten as it emerges from the shadow of the Earth. The Moon completely leaves the Earth's shadow at 5:01 a.m..
Lunar Eclipse Sleepover
Watch the lunar eclipse with family and friends. Invite family members and or friends over and have a "lunar eclipse sleepover." Everyone brings warm clothes, blankets and lawn chairs. Don't forget your lunar eclipse snacks, moon pies and lots of hot chocolate. Make a party out of the lunar eclipse event.
Staying up late for a lunar eclipse is actually a great reason of a family outing or a sleepover in the backyard. Besides, no one really sleeps much on a sleepover. Remember if you have school the next day, take an early nap. Ask your parents if you can go to bed early and set the alarm for the lunar eclipse.
1. Decide whether the Earth is spherical or flat. While watching the lunar eclipse, observe the shape of the Earth's shadow on the Moon. A flat Earth will make a straight-line shadow, a spherical Earth will cast a shadow on the Moon that looks like part of a circle.
2. Which is bigger the Earth or the Moon? Look at the shadow of the Earth on the Moon. If the Earth is smaller than the Moon, the Earth's shadow will be smaller than the Moon. If the Earth is bigger than the Moon the shadow of the Earth falling on the Moon will be larger than the size of the Moon.
3. Record what you see! Bring a clipboard, paper and pencil to draw what you see during the lunar eclipse. Bring along a clock or a watch to record the time of your recorded observation. Crayons might come in handy as you record any color changes.
4. While watching the lunar eclipse, use your imagination to imagine yourself sitting on the Moon (safely in a warm spacesuit) looking back at the Earth. What would the Earth look like during the lunar eclipse? What phase would the Earth be in from the Moon? Do you think you could see any of the light pollution from large cities as a glow around population centers?
5. During the time the Moon is totally within the Earth's shadow, the expected color of the Moon should be darkened to grey or black. However, from the Moon looking back at the Earth, the Sun would be completely blocked and all you would see would be a ring of sunrises and sunsets. This sunrise/sunset ring would be the only light falling on the Moon. What color do you expect the Moon to appear during a total lunar eclipse? What color was the Moon during this time?
Have fun moon watching and have a safe and happy holiday!
Libby and Robert Strong and Richard Pollack work with the SMART Center, a hands-on science outreach and education organization in the northern Ohio Valley, the headquarters of which is located at the SMART Centre Market, 30 22nd St., Wheeling. Visit them at www.smartcenter.org.