Saturday, January 16, 2010

10 things you must know about eclipses

Whenever an eclipse occurs, a lot of questions come to our mind which those remain unanswered. Here are a few things that you must know about the eclipses:

1. What is an eclipse? What are its types?UP
Eclipse is a total or partial obscuration of light from a celestial body as it passes through the shadow of another body. Or simply, eclipse is a temporary disappearance of sun or moon obscured by shadow of either moon or the earth respectively. Primarily, eclipses are of two types: solar and lunar. These are further classified as complete or partial eclipses. Annular eclipse is a special forma of solar eclipse.

2. How does an eclipse occur?UP
While revolving in their respective orbits when sun, moon, and the earth happen to be in a same plane, an eclipse would occur. When the moon comes between the sun and the earth, it obscures the sun from an observer at the surface of earth and a solar eclipse occurs. Similarly, when the earth comes between sun and moon, a lunar eclipse would occur.

3. Do eclipses occur on some special days?UP
Yes. A solar eclipse can occur only on new moon day and a lunar eclipse can occur only on a full moon night, because these are the only days on which these three bodies come in a same plane. But not on each new moon or full moon day an eclipse would occur. They occur only when the sun, moon, and the earth comes exactly in a same plane.

4. How is it possible for the moon to obscure the sun completely though it is too small compared to the sun?UP
Indeed the moon is 400 times smaller than the sun, but it is also 400 times nearer the earth. As a result, sun and moon have almost exactly the same angular size (about 0.5%) so that it is possible for the moon to obscure the sun. We can hide the sun from our sight by just bringing our palm in front of our eyes. It's just like that.

5. How do the complete and partial eclipses occur?UP
The earth and moon both cast two types of shadows in sunlight: the shadow having a dark cone-shaped inner region--the umbra--and an outer lighter penumbral region. A solar eclipse occurs when the moon passes directly in front of the sun so that the earth lies in the moon's shadow. When the moon is sufficiently close to the earth so that its apparent diameter exceeds that of the sun, then the umbra of the moon's shadow just reach the earth's surface. It moves in a general west to east trend over a very narrow curved zone on the surface, which can be up to 250 km wide, but averages about 160 km. An observer at a point where only the penumbra will move can only see a partial eclipse. An observer in the path on umbra will experience a total eclipse.

6. What is an annular eclipse? What is a diamond ring?UP
If the moon is far enough away to appear smaller than the sun, a rim (or annulus) of light will be seen around the eclipsed sun and an annular eclipse will occur. The period of annularity never exceeds 12.5 minutes and is normally much less.

At the time of complete solar eclipse, when only a small corner of sun is visible behind the moon, it looks like a diamond. When this phenomenon occurs with an annular eclipse, it looks like a diamond ring and is generally termed so.

7. How long can an eclipse run?UP
As already stated, an annular or complete eclipse never exceeds 12.5 minutes and the average time or it is much more less. However, a solar eclipse from its first touch to its complete release can take up to four hours. The maximum duration of a complete lunar eclipse is 1 hour 42 minutes.

8. Why does not the moon disappear even during a complete lunar eclipse?UP
The moon can usually be seen throughout totality of the eclipse being illuminated by sunlight refracted by the earth's atmosphere in the shadowed area. Since the bluer wavelengths are removed by scattering, the moon has a coppery red colour.

9. Is an eclipse a rare phenomenon?UP
No. Up to seven eclipses can occur in a year, either five solar and two lunar or four solar and three lunar.

10. Do eclipses cause any harm to human life?UP
10. No. An eclipse is a completely celestial phenomenon and it has noting to do about human beings. The funny mythological fables about eclipses that Rahu and Ketu swallow sun and moon during the eclipses are noting but superstitions.

Here is a video link about how an eclipse occur. Just check it. Any questions? Queries? Comments? Let me know.

1 comment:

  1. hey gr8 info about eclipses...
    keep up the good work...


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