Figure 1
pQFWhat kind of solar eclipses are there ? |
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There are two kinds of solar eclipse, total solar eclipse and annular solar eclipse. The reason why two kinds of solar eclipse occur is as follows.The sun's real diameter is 400 times as large as the moon's diameter, but distance till the sun is 400 times as far as the moon. Therefore, both the sun and the moon can be seen almost in the same apparent size. However, apparent size of the sun and the moon changes. If the moon's apparent size is larger than sun's, then total solar eclipse can be seen. On the other hand, if the moon's apparent size is smaller than sun's, then annular solar eclipse can be seen. The reason why the apparent size of the moon and the sun changes is as follows. The moon's orbit is elliptic, so the moon's distance from the earth changes, and apparent size of the moon changes. Also, the earth's orbit is elliptic, too. Therefore the sun's distance from the earth also changes a little bit, and apparent size of the sun changes a little. Apparent size of the moon changes much more than sun's, since moon's orbit is much more elliptic than the earth's. Earth's orbit is elliptic, but it is almost circle. Therefore, when the moon is close to the earth (and sun is far), then shadow cone by the moon reaches the earth, and it makes umbra. In the umbra, total solar eclipse can be seen (Figre 1). On the other hand, when the moon is far (and sun is close to the earth), then shadow cone by the moon does not reache the earth, and annular eclipse can be seen (Figure 3). Partial eclipses can be seen around the area where total eclipse or annular eclipse is seen. |
