Xref: utzoo talk.politics.misc:8575 sci.misc:1162
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From: orb@whuts.UUCP (SEVENER)
Newsgroups: talk.politics.misc,sci.misc
Subject: Darren Leigh at the Edge of Space! :Part I
Message-ID: <4009@whuts.UUCP>
Date: 25 Mar 88 13:20:24 GMT
References: <3405@bloom-beacon.MIT.EDU> <3884@whuts.UUCP> <2177@mit-amt.MEDIA.MIT.EDU>
Reply-To: orb@whuts.UUCP (45263-SEVENER,T.J.)
Organization: AT&T Bell Laboratories, Whippany, NJ
Lines: 48

In article <2177@mit-amt.MEDIA.MIT.EDU> dlleigh@media-lab.MEDIA.MIT.EDU (Darren L. Leigh) writes:
>In article <3884@whuts.UUCP> orb@whuts.UUCP (45263-SEVENER,T.J.) writes:
>>
>>My, what a crop of scientific genuises we are training
>>up at MIT!!
>     I suggested there might be an abrupt shift from the atmosphere
>     to space at the edge of the atmosphere.  A poster has suggested
>     this is not correct.  Personally I don't know.
>     Logically, it seems to me that there will be some kind of
>     abrupt shift or discontinuity at the point of escape from the
>     Earth's gravity.  On the other hand, air is an amorphous gas
>     which is not rigidly bound and constantly in motion.  So this
>     will blur the boundary.
>
>Isn't this rich?  Obviously Tim hasn't heard Newton's law of universal
>gravitation (F = GMm/(r^2)) or at least he doesn't understand it.
>With Tim's understanding of physics at this level, I feel it best that
>we ignore his postings on the subject for the time being.

I repeat again:
My, what a crop of scientific geniuses we are training up at MIT!!

Mr. Leigh, I beg to bring your attention to the following article
in the Britannica Micropedia, p.554, on a concept I suppose you haven't
heard of, called "escape velocity":

"escape velocity, in astronomy and space exploration, the velocity
that once attained is sufficient for a body to escape from a
gravitational centre of attraction without undergoing any
further acceleration.  Escape velocity decreases with altitude,
and is equal to the square root of 2 (1.414) times the velocity
necessary to maintain a circular orbit at the same altitude.
At the surface of the Earth, if atmospheric resistance could be
disregarded, escape velocity would be about 11.2 km (6.95) miles
per second.  The velocity of escape from the less massive Moon
is about 2.4 km (1.5 miles) per second at its surface.  A planet
(or satellite) cannot long retain an atmosphere if the planet's
escape velocity is low enough to be near the average velocity 
of the gas molecules making up the atmosphere."

One might also add that there comes an altitude at which the
escape velocity approximately equals the average velocity of
the gas molecules making up the atmosphere.  This is the
"abrupt end" of the atmosphere.

More from a classic paper on the subject in Part II...

tim sevener  whuts!orb