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Eclipses occur
when the moon moves into a position where it is directly
aligned with the sun and the earth. At this time the sun, the earth and
the moon must be very nearly, if not precisely aligned.
There are two basic types of eclipses – lunar and solar. A total LUNAR
ECLIPSE occurs when the full moon passes through the shadow of the earth.
In this case, the earth is between the sun and the moon. During a lunar
eclipse you can see the bright moon darken - sometimes to a reddish brown
color. A lunar eclipse can last for an hour or more.
A
total SOLAR ECLIPSE occurs when the new moon passes directly between
the sun and the earth. For a few minutes, the moon totally obscures
the bright sun and casts a narrow shadow on the earth, turning
daytime into an eerie darkness.
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 This narrow shadow on the earth is called the umbra. The umbra
sweeps across the earth at over 1,000 miles an hour. The umbra in
2008
will be no wider than 223 kilometers (138.5
miles) across.
Just outside this narrow path of
totality, there is a partial shadow called the penumbra, where a section
of the sun’s bright disk can be seen.
Before totality, a phenomenon
called "Bailey’s beads" occurs. |
The beads appear around the edge of the moon,
when the last rays of sunlight shine through the irregularities
 of
the moon's surface.
During totality birds begin to roost; nocturnal animals prepare to start
their day; diurnal animals prepare for the night; and the stars become
visible. It is during these few minutes as the moon totally obscures the
sun, that the sun’s halo, the corona, comes into view.
Total solar eclipses are rare. They do not occur every month. This is
because the orbit of the moon is tilted by about five degrees in relation
to the earth’s orbit. And normally the moon passes just above or below
the line between the sun and the earth. So at most new and full moons, the
shadows miss the earth and there is no eclipse. The right eclipse
conditions occur about every six months.
There are fewer than 70 total solar eclipses each century, so for most
folks, this is a once-in-a-lifetime happening! |
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