Why doesn't the sky fall?

[J.Oddino]

Ding, ding, ding!! We've got some really smart guys on this list.
The air molecules are constantly colliding with each other in perfect elastic collisions so they don't slow down.  They are light so you don't feel them hit your skin but the combined effect is to create the pressure that keeps us together.
Jim O
  ----- Original Message ----- 
  From: randy10926 at comcast.net 
  To: discussion at nsrca.org 
  Sent: Monday, August 15, 2005 2:22 PM
  Subject: Re: Why doesn't the sky fall?


  Air molecules are never at rest. They undergo constant random thermal motions of a variety of types. The simplest type is that of uniform translation. The mean speed is about 500 m/s which is greater than the speed of sound (340 m/s). 

  Randy

    -------------- Original message -------------- 

    I thought it was time to stir the pot while we wait for the results from the Worlds.
    Can anyone explain why gravity doesn't pull all the air molecules down to earth?  Are they lighter than space?  What is their mean speed?
    I don't think this will help answer the weathervaning question and won't help us fly any better but I thought it might be fun.
    Jim O
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