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Large, Persistent Eclipse/Shadow On Earth?

  1. Jun 23, 2015 #1
    This may sound like a dumb question, but I have been curious about this for a while. What would happen if something cast a large and persistent shadow on the same part of earth? Say the shadow was the size of the umbra during a total solar eclipse. What would that do to the earth? I know the moon cannot do that, but if something could, then what?
  2. jcsd
  3. Jun 23, 2015 #2
    Well the night side of Earth is in a permanent shadow by definition, although of course the rotation of Earth means that the shadow is not always at the same place wrt Earth's surface.
    If the Earth did not rotate the darkened side would always be cooler, quite possibly frozen in parts, although I expect that this would be mitigated to some extent by atmospheric and ocean circulations.
    Last edited: Jun 23, 2015
  4. Jun 23, 2015 #3


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    Any "permanent" shadow of that type would reduce the amount of solar radiation striking the Earth, cooling it slightly. The Moon's shadow during an eclipse is never more than ~267 km across, and would block less than 1/5 of a percent of the Solar radiation hitting the Earth, so I wouldn't expect too much in the way of cooling. What effect such a permanent shadow spot would have on weather patterns is hard to say.
  5. Jun 30, 2015 #4


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    Also, where the shadow is cast is also important. Normally, during a solar eclipse the area eclipsed will see some drop in temperature. If the solar eclipse happens in say Canada in February and during an unusually warm day ie 40 degrees F, the temperature will drop to below Zero, and do so as the eclipse starts to cover the sun ie you will experience a 40-50 degree drop in temperature in about an hour. This is not speculation, but an actual personal experience (year 1979).
    On a side note; because it was so warm prior to the eclipse, there was some humidity vs if it were colder, there would have been a lot less moisture in the air. This caused all the expensive cameras to freeze up. Only one or two prepackage cheap cameras actually worked (the kind that were disposable and dropped off to be processed, another item of the past).
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