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What if there were no atmosphere

  1. Mar 2, 2013 #1
    What would be the effect on day night period if there were no atmosphere? I mean would the days become longer or shorter? Why?PS:Admims,Trust me its not my homework...
     
  2. jcsd
  3. Mar 2, 2013 #2

    Dale

    Staff: Mentor

    The days and nights would be the same length, but there would be no twilight.
     
  4. Mar 2, 2013 #3

    russ_watters

    User Avatar

    Staff: Mentor

    Depending on how precise you want to be, you'd get a few less minutes of the sun being up due to the elimination of atmospheric refraction. Roughly 1 solar diameter at the horizon equals about 4 extra minutes each at sunrise/sunset if the sun is setting vertically:
    http://en.wikipedia.org/wiki/Atmospheric_refraction

    [edit: er - I calculated 2 min, but thought I remembered it being 4.]
     
  5. Mar 2, 2013 #4
    The earth's moment of inertia would be less,so angular velocity must increase to conserve the angular momentum... So day and night should be shorter...
    Actually I asked the question,because many things can happen... I want to know what else are the factors?
     
  6. Mar 2, 2013 #5

    Dale

    Staff: Mentor

    Oh, interesting.
     
  7. Mar 2, 2013 #6

    Dale

    Staff: Mentor

    No, its angular momentum would also be less, so there would be no change.
     
  8. Mar 2, 2013 #7

    russ_watters

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    Staff: Mentor

    Conserve from what? We have to make up a story about how it lost its atmosphere or came to exist without one without changing its angular momentum. Now this is just idle speculation and storytelling.
     
  9. Mar 2, 2013 #8
    russ_waters: yeah that's a big effect... Do u think my logic is logical?
     
  10. Mar 2, 2013 #9
    now the earth has to rotate with its atmosphere... So wouldn't the 'w' be a higher value if there's no atmosphere...
     
  11. Mar 2, 2013 #10

    Dale

    Staff: Mentor

    No, why should it. The atmosphere has angular momentum. If it didn't exist then the earth would have less angular momentum.

    Now, if you are not just thinking of a "with vs without" scenario, but are rather thinking of a "before vs after" scenario, then you need to specify the process you are considering for removing the atmosphere.
     
  12. Mar 2, 2013 #11
    If there was no atmosphere the oceans would evaporate. If the earth had lost it's atmosphere 4 billion years ago, just as mars did, it would now rotate at a higher speed since the tidal forces would be smaller.
     
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