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From: cmpbsdb@gitpyr.UUCP (Don Barry)
Newsgroups: net.physics,net.space,net.research
Subject: Re: Star-Wars/Space Telescopes (parabolic mirrors)
Message-ID: <1124@gitpyr.UUCP>
Date: Mon, 2-Dec-85 02:44:07 EST
Article-I.D.: gitpyr.1124
Posted: Mon Dec  2 02:44:07 1985
Date-Received: Tue, 3-Dec-85 08:37:26 EST
References: <384@ukc.UUCP> <26@sbcs.UUCP>
Organization: Georgia Institute of Technology
Lines: 17
Xref: watmath net.physics:3649 net.space:4834 net.research:368

In article <26@sbcs.UUCP>, debray@sbcs.UUCP (Saumya Debray) writes:
> Seems to me that since air pressure is the same in all directions, this
> would give a spherical rather than a parabolic mirror.
By the same argument, a suspended string would form a spherical arc - 
instead, the form is a catenary, described by the hyperbolic functions.
I am unaware of the figure of equipressure deformation of an elastic disc,
but one technique that is used to generate true parabolas in a uniform gravity
field is that of spin-molding.  It is an easy matter to calculate the
equipotential surface of a spinning liquid, and imposing the condition of
stability, the figure is a paraboloid.

-- 

Don Barry (Chemistry Dept)          CSnet: cmpbsdb%gitpyr.GTNET@gatech.CSNET
Georgia Institute of Technology    BITNET: CMPBSDB @ GITVM1
Atlanta, GA 30332      ARPA: cmpbsdb%gitpyr.GTNET%gatech.CSNET@csnet-relay.ARPA 
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