
Explanation of Solar Eclipse
Solar eclipse occurs when the Moon
is in line between the Earth and the Sun (see Figure 1). The Moon cast a shadow
on the Earth's surface and obscurs some parts on the Sun. The porportion of
the Sun being blocked depends on the position of the observer on the Earth.
When only the Moon's penumbral shadow strikes the Earth, a partial eclipse of
the Sun is observed. However, if the Moon's dark umbral shadow sweeps across
Earth's surface, a total eclipse of the Sun is seen.

Figure 1 Relative
positions of the Sun, the Moon and the Earth during a total solar eclipse
Sometimes the Moon is farther away
from the Earth and its umbral shadow is not long enough to reach the Earth.
The Moon appears smaller than the Sun and cannot completely cover it (see Figure
2). Instead, the 'antumbral' or negative shadow reaches the Earth. If you are
within this shadow, you will see an eclipse where a ring or 'annulus' of bright
sunlight surrounds the Moon at the maximum phase. Those within the penumbra
would observe a partial eclipse.

Figure 2 Relative
positions of the Sun, the Moon and the Earth during an annular solar eclipse
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