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Last Post 10/17/2011 7:25 AM by  Terry Kucera
How long are eclipses
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10/16/2011 8:39 PM

    rebecca a

    what's the difference in length of time of a "total-eclipse" of the moon, or the sun, which one last's longer?


    Terry Kucera



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    10/17/2011 7:25 AM

    Hi Rebecca,

    Totality for a solar eclipse at any one locations just lasts for a few minutes, while totality for a lunar eclipse can last for over an hour.

    During a lunar eclipse Earth casts a large shadow on the Moon and is actually cutting off light hitting the moon rather than blocking it from the observer. As a result, a lunar eclipse can be seen from anywhere the moon is visible for as long as it is occurring.

    On the other hand, in a total solar eclipse the actual moon has to come between the Earth and Sun and be aligned just right, which only happens for a few minutes at amy one location.

    Looking at sketches of the geometry might help. Here are some (none of them to scale!)

    Here is an animation of how a solar eclipse works.
    http://sunearthday.nasa.g...terials/ecl_anim.mov
    And a sketch
    http://www.total-eclipse-...eclipse/geometry.php
    The location from which you can see the total solar eclipse is very specific and shifts quickly across the globe.

    Here, on the other hand, is one of a lunar eclipse.
    http://www.mreclipse.com/Special/image/LEDiagram1c.JPG
    The shadow the the Earth on the moon is large and can be seen from a broad area.

    cheers,

    Terry




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