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Gas density and mass (Attraction towards Earth)

  1. Feb 12, 2015 #1
    How ozone having higher molecular mass then oxygen and CO2 is on a certain upper level of atmosphere?
    Doesn't the more dense objects come closer to ground by gravitation?
  2. jcsd
  3. Feb 12, 2015 #2


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    Staff: Mentor

  4. Feb 12, 2015 #3
    Okay but what about the high molecular mass?
    Why above CO2?
  5. Feb 12, 2015 #4


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    Ozone is constantly being created by sunlight in the upper atmosphere, but it is also breaking down constantly as well, because ozone is unstable.

    Also, gases stratify by molecular weight only in a situation where conditions permit. One of those conditions is that no mixing is occurring, due to temperature differences, for example. The atmosphere is a dynamic object, with the uneven temperature conditions created by having one portion heated by the sun causing winds to develop, which winds promote mixing of the atmosphere's constituent gasses.

    There is a small amount of ozone present closer to the ground, but at these low altitudes, ozone is considered a pollutant, due in part to its oxidizing characteristics.
  6. Feb 12, 2015 #5
    What is that particular condition that ozone is being created in upper atmosphere?
    By distance above the ground what is happening?
  7. Feb 12, 2015 #6
    Photochemical reactions.
  8. Feb 12, 2015 #7
    Sorry, I am meaning that why can't photochemical reaction start at ground level?
    Why only small amount of ozone at ground level?
    Last edited: Feb 12, 2015
  9. Feb 12, 2015 #8


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    To a certain extent, the reaction creating ozone does occur close to the surface of the earth, but at ground level, the intensity of the solar radiation reaching the ground is diminished by the blocking effect of the atmosphere itself. In the upper levels of the atmosphere where most of the ozone is created, the great majority of the atmospheric mass lies below, and the solar radiation responsible for creating ozone is much stronger.
  10. Feb 12, 2015 #9
    Thanks to all of you.
  11. Feb 12, 2015 #10
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