Why doesn't the sky fall?

[spbyrum]

Jim

Adam ate the apple.  That's where he got it trouble.  Should have known
better.  The girl was pulling one on him.

Steve Byrum 

-----Original Message-----
From: discussion-request at nsrca.org [mailto:discussion-request at nsrca.org]
On Behalf Of Jim Ivey
Sent: Monday, August 15, 2005 7:09 PM
To: discussion at nsrca.org
Subject: Re: Re: Why doesn't the sky fall?

Wayne
Tho't that was ADAM.
 Jim Ivey
> 
> From: "Wayne Galligan" <wgalligan at goodsonacura.com>
> Date: 2005/08/15 Mon PM 06:32:37 EDT
> To: <discussion at nsrca.org>
> Subject: Re: Why doesn't the sky fall?
> 
> SO..... in other words... Newtons theory about the apple falling on
his head about sums it up.... right?
> 
> WG
> 
>   ----- Original Message ----- 
>   From: randy10926 at comcast.net 
>   To: discussion at nsrca.org 
>   Sent: Monday, August 15, 2005 4:35 PM
>   Subject: Re: Why doesn't the sky fall?
> 
> 
>         At the top of a planet's atmosphere, particles are running
around in all directions, at all of the various speeds corresponding to
the kinetic temperature, and to the predictions of the Maxwell-Boltzmann
distribution. Some of the particles will be headed upwards, some
downwards, and some sideways. Some of them will be moving slowly, some
at an average speed, and some very quickly. Whether a planet will hold
onto an atmosphere will depend upon the motions of those particles which
happen to be moving upwards at a much higher than average speed. If
those particles are moving upwards at less than the planet's escape
velocity (the speed which an object must be traveling at in order to
escape the planet's gravity, and go off into space), then the particles
will follow curved paths which are ellipses with a focus at the center
of the planet, and will go up for a while, and then fall back into the
atmosphere. (This discussion assumes that we are in the very outermost
reaches of the atmosphere, where there is so little gas that the
particles don't collide with other particles very often. If we were
talking about a lower region, the particles would be deflected from
their paths, and change their energies, so frequently that any
discussion of motions which resemble orbital motions would be
pointless.)
>         However, if the particles were moving upwards faster than the
planet's escape velocity, they would follow hyperbolic paths which would
take them out into space, never to return. Of course, only those
particles which happened to be heading upwards at very high speeds would
follow such paths, but as already discussed, there is a continual
shuffling of particle motions and speeds, and as a result, in a short
while, particles which did not originally have such motions would end up
with motions identical to those particles which had been lost, and then
those particles would also be lost.
> 
> 
>   Simple ain't it.
> 
>   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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