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RE: Whats in Helium?



Here is my theory:  When the balloon is "at pressure", the pressure gradient
between inside and outside is greatest, and the interstices in the rubber
are largest, due to the fully stretched condition of the membrane.  As the
helium diffuses out, the pressure falls and the holes become smaller,
reducing the rate of flow.  The test for this would be an analysis of what
remains to see if is Helium of the same purity as what was originally put
into the balloon.  Perhaps one could extract the remainder and use it to
pump up a much smaller balloon to full inflation.  If that floats, we would
have some evidence for my theory.

Well, it has been almost 37 years since my last physics course.  73 de Brian
W3BW

-----Original Message-----
From: owner-AMSAT-BB@AMSAT.Org [mailto:owner-AMSAT-BB@AMSAT.Org]On
Behalf Of Phil Karn
Sent: Friday, March 10, 2000 7:43 PM
To: kp4te@mail.tld.net
Cc: bruninga@nadn.navy.mil; amsat-bb@AMSAT.Org
Subject: Re: [amsat-bb] Whats in Helium?


>Helium is a noble gas, that it is not a natural occurring gas.  It is not
made
>by compressing the atmosphere air.  It is a United States strategical
element

Uh, Helium *does* occur naturally, though it is present in the earth's
atmosphere only in trace amounts. That's because the thermal velocity
of a helium atom at earth temperatures exceeds the earth's escape
velocity, i.e., the earth's gravity cannot retain it in its
atmosphere. This means helium is not a renewable resource; once you
let it go into the atmosphere, it is gone forever.

The primary source of helium is as a constituent of certain natural
gas supplies, primarily in the US. It is produced over geologic time
(i.e. very slowly) by the alpha decay of naturally occurring
radioactive elements such as uranium and thorium; an alpha particle is
merely the nucleus of a helium atom.

Phil
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