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<DIV>Even in the bottom half of the atmosphere the density of air is so low that it is mostly space. But even at this low density - on average an 'Air molecule' collides 5 times a nanosecond. 'Air Molecule' is a generalization for the air mixture which contains O2, CO2, H2, etc. Some particles are molecules, some atoms, some ions, some ad nasuem. The generalization is used to develop mathemical or computer models of the atmosphere.</DIV>
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<DIV>And at the size of an 'Air molecule' we are starting to get in the areana where just plain old classical physics has some problems and other forms of physics are introduced to help explain what is going on.</DIV>
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<DIV>randy</DIV>
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<DIV><FONT face=Arial size=2>That probably explains why I smell it so fast when somone lights a match in the house.</FONT></DIV>
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<DIV><FONT face=Arial size=2>BTW, I don't think there is an "air molecule", it is a gas mixture and it is packed rel tight on the bottom. Half of the atmosphere is below 18,000 feet. </FONT></DIV>
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<DIV>John Ferrell <BR><A href="http://dixienc.us/">http://DixieNC.US</A><BR></DIV>
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<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B> <A title=randy10926@comcast.net href="mailto:randy10926@comcast.net">randy10926@comcast.net</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A title=discussion@nsrca.org href="mailto:discussion@nsrca.org">discussion@nsrca.org</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Monday, August 15, 2005 5:22 PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: Why doesn't the sky fall?</DIV>
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<DIV>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). </DIV>
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<DIV>Randy</DIV>
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<DIV><FONT face=Arial size=2>I thought it was time to stir the pot while we wait for the results from the Worlds.</FONT></DIV>
<DIV><FONT face=Arial size=2>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?</FONT></DIV>
<DIV><FONT face=Arial size=2>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.</FONT></DIV>
<DIV><FONT face=Arial size=2>Jim O</FONT></DIV></BLOCKQUOTE></BLOCKQUOTE></BLOCKQUOTE></body></html>