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This coming February 26th, we will be treated to another celestial event in the unending dance of the planets. On that day, the moon will move exactly between the earth and the sun. The moon's shadow will fall across the earth, and a few lucky people in the right places will see a total solar eclipse. Those of us not lucky enough to live in these places will travel thousands of miles to see this event.
To see a total solar eclipse, you have to be in just the right spot on the earth. When you look up in the sky at the sun and the moon, you notice a strange coincidence--both look the same size in the sky. Now, they're not really the same size. The sun's diameter is actually 400 times the moon's diameter. But, you must also take into account that the sun is also 400 times further away from the earth, reducing its apparent size to the same as the moon's. Because of this relationship, when you are standing on the earth, looking up at the two, you must be in a very limited area to see the moon cover the entire face of the sun. If you were to move a little north, the sun would peek out over the top of the moon; a little south, and the sun shines past the bottom of the moon. The match is so good that the "path of totality" is never more than 167 miles in diameter, and is usually less. This means that very few people have seen a total eclipse because the shadow only covers a very small area on the earth. |
This
diagram (wildly out of scale) shows a side view
of the alignment. From anywhere in the
grey penumbra, you will see some part of the sun
shining from behind the moon. The
penumbra is the area of partial eclipse. Only
from within the tiny area where the
dark umbra touches the earth will you see the
sun completely covered and witness a
total eclipse.
The earth
and the moon are not fixed objects. The moon is
busy orbiting the earth. The earth is busy orbiting
the sun and also rotating on its axis. This means
that the spot on the earth where the umbra falls is
always moving and actually traces out a
path.
This diagram (wildly out of scale) shows a side view of the alignment. From anywhere in the grey penumbra, you will see some part of the sun shining from behind the moon. The penumbra is the area of partial eclipse. Only from within the tiny area where the dark umbra touches the earth will you see the sun completely covered and witness a total eclipse. The earth and the moon are not fixed objects. The moon is busy orbiting the earth. The earth is busy orbiting the sun and also rotating on its axis. This means that the spot on the earth where the umbra falls is always moving and actually traces out a path. |
This
diagram shows the path of the umbra for the
eclipse on February 26th, 1998. Only the central
lines mark out the path of the umbra. The much
wider area shows the path of the larger
penumbra, where a partial eclipse can be seen.
(Note the percentages of total in the penumbral
regions.)
This diagram shows the path of the umbra for the eclipse on February 26th, 1998. Only the central lines mark out the path of the umbra. The much wider area shows the path of the larger penumbra, where a partial eclipse can be seen. (Note the percentages of total in the penumbral regions.) |
The shadow first touches down near the equator out in the Pacific Ocean. It travels eastward and first sees land at the Galapagos Islands, where it brushes past the northen-most island. Then it falls in Panama and Colombia, where the eclipse passes over the cities of Montería, Sincelejo, Magangué, Valledupar, and Maracaibo. The path nicks northern Venezuela and then heads out into the Carribean, where it will pass over the islands of Aruba, Curaçao, Montserrat, Antigua, and Guadeloupe. From there, the shadow sweeps out into the Atlantic Ocean before it takes off into space.
 Go Back |
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Why Eclipses Happen |
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This resource is presented by The Exploratorium and NASA's Sun-Earth Connection Education Forum. |
The Exploratorium 1998 |