Eclipses: Solar and Lunar
|There has long been confusion
about exactly who gets in front of whom during an eclipse. The following diagrams
and explanations may help you sort out what is happening when you see either a solar
eclipse or a lunar eclipse.
Eclipses are named for the body that is being darkened by a shadow, either totally or partially. Therefore, if you have a Solar Eclipse, the sun will be covered by a shadow. If you have a Lunar Eclipse, the Moon will be covered by a shadow.
Our sun's name is Sol. A
solar eclipse occurs when the New Moon comes between the Earth and the sun.
The term New Moon refers to one of the Moon's phases. When you have a Full Moon, we can see the entire face of the Moon, because Earth is positioned in such a way that we can see the entire face of the Moon because of reflected sunlight hitting the Moon. A New Moon is a Full Moon that isn't lighted by either sunlight or reflected light from Earth, because it is between us and the sun, and the sun is lighting the Moon's "backside" from our point of view.
solar eclipse of December 25, 2000 was a partial solar eclipse, with only about 1/3 of
the sun covered by the New Moon.
There are several different types of solar eclipse.
The most common kind of solar eclipse is the Partial Eclipse. During a Partial Eclipse, the Moon is not positioned close enough to the Earth, or directly on the Earth's equatorial plane, so that it would completely block out the sun. It only blocks an edge of the sun.
A Total Solar Eclipse occurs when the New Moon is placed just right that it completely covers the face of the sun, as we see it from Earth.
The most rare solar eclipses are the annular eclipses. Annular Eclipses are so named because the New Moon almost covers the entire face of the sun, but...not quite. A thin ring (annulus) remains. Of the Annular Eclipses, the most rare is a Broken Annularity.
Here is an example of a Broken Annularity. The Moon was so close to the Earth that it almost completely blocked out the sun. The ring is "broken" by mountains on the Moon, and the Lunar Maria (seas) dip in enough that more sunlight can get past, and you see a few gold areas where the sunlight is trying to escape.
One of the most interesting things about solar eclipses is the way that they affect Earth.
During partial eclipses, you can enjoy tiny eclipse images sparkling on the ground as the sunlight is filtered through leaves. Each tiny hole formed from the spaces between the leaves allows a projection of the eclipse image to shine through onto the ground, much like a "pin-hole projector." Sometimes, if it is close to being a Total or Annular eclipse, the wind will blow, and the temperature may drop quite a bit.
During Total or Annular
Eclipses, you begin to understand just how important the sun is to Earth. Not only
does the sky get as dark as night as the sun's light is blocked, but strong winds spring
up due to the rapid and uneven cooling of the Earth in the path of the eclipse. Even
in summer, it might get so cold that you want to put on your winter
Another interesting effect of these dark eclipses is the presence of "shadow bands." The sighting of shadow bands is relatively rare...they are not always spotted during an eclipse, but if you ever see them, you won't forget them. They resemble clear, dark grey strips of crepe paper lined up row after row with about the same amount of open space between the strips as the strips are wide. When the event begins, they appear to simply be lying on the ground. As the event progresses, however, they appear to move toward you, undulating over the ground, following the contours of the ground that they appear to move over. It can be a rather frightening experience, even if you know what is happening. Your body has its own idea of what is "right," and strips of ground crawling toward you are not acceptable...even if your mind says it's OK. Your body may want to run and hide, anyway.
And...during some eclipses, different areas along the path may experience monochromatic (one color) light. This follows the entire spectrum--red, orange, yellow, green, blue, and violet. Indigo is more difficult to distinguish from the blue and violet, however. Interesting things happen when you are exposed to monochromatic light. For instance, if the light is green, each blade of grass seems to stand out in 3-D...even the blades partially covered by other blades of grass. In green light, red turns to the grey scale. Red clothing looks black or dark grey. People's skin looks greyish, too....that can be rather unnerving.
There are a lot of myths about the danger of solar eclipses. Although it IS dangerous for you to look directly at the sun at any time, glancing at an eclipse would pose less danger in that a portion of the sun's rays are blocked. The temptation to keep looking, however, makes looking at an eclipse dangerous. There are special filters made so that people can look at the sun safely, and without them (used properly), you should never look directly at the sun. There are also other ways to look at a solar eclipse without looking directly at the sun. You can use "pin-hole projection," or a "pin-hole mirror ."
Eclipse light can't make you go insane, or any of the other myths that abound regarding the filtered light from the sun. It is the same light that you normally get, except for the fact that some of it is being blocked by the Moon getting in the way.
It is easy to understand why
Solar Eclipses are the subject of superstition, however, if you have ever experienced a
total or annular type of eclipse. It can be frightening...the strong winds almost
knocking you over, and the temperature dropping just as the light goes out.
Our Moon's name is Luna. A Lunar Eclipse occurs when the Earth gets just in the right place between the Sun and the Moon, and Earth casts a shadow on the face of the moon.
This shadow can be a partial eclipse of the Moon, or a total eclipse, just as for solar eclipses.
If the shadow cast is just a partial covering, it generally looks shadow-grey. If it is a total eclipse of the Moon, however, the light that does bend around the Earth from the sun is mainly the red spectrum, and it colors the face of the Moon red...sometimes, even a bright cherry red.
During a Lunar Eclipse, you don't have the drastic effects on Earth that you have with a Solar Eclipse. Although both Full Moon and New Moon affect the tides, there is no great change in temperature, or winds. The light that we see on the face of the Moon is reflected light...the Moon does not make its own light. Since it doesn't make light, it also doesn't make heat. Therefore, there are no great temperature differences if the light on the face of the Moon is blocked by our (Earth's) shadow for a while.
You don't need any special filters to view a Lunar Eclipse.
One of the most interesting things about a lunar eclipse is that it shows the shape of Earth...the eclipse shadow demonstrates a circular object casting the shadow. It also demonstrates that the body casting the shadow is considerably larger than the Moon (4 times). Otherwise, if it was a smaller body so close to the Moon that it could cast that large a shadow, it would be drawn by gravitation to impact the Moon, and that would probably destroy both bodies.
Other than the reddish color generally evident with a Total Lunar Eclipse, there isn't really much excitement about Lunar eclipses--no scary myths and legends. They are nice to watch, however, because it is fun to see our planet's shadow projected into space as though the Moon was a giant projection screen put up just for us to enjoy.
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