From: Chuck Simmons
Organization: You jest.
X-Mailer: Mozilla 4.61 [en] (X11; U; Linux 2.0.33 i586)
Subject: Re: O.T. Math help
References: <3DC730B0.5FDAB60E@rica.net> <3DC738EC.44458C98@webaccess.net> <3DC7C3FF.7ABC2433@webaccess.net>
Date: Fri, 08 Nov 2002 02:26:07 GMT
NNTP-Posting-Date: Thu, 07 Nov 2002 18:26:07 PST
Jim Thompson wrote:
> On Thu, 7 Nov 2002 19:32:37 -0600,
> "jcurtis" ,
> In Newsgroup: sci.electronics.design,
> Article: ,
> Entitled: "Re: O.T. Math help",
> Wrote the following:
> |My friend, glass does flow. Any competent glass worker will tell you that a
> |glass pane is somewhat thicker at the bottom than at the top, although it
> |takes many years for this to be measurable.
> Very true! My ancestors date back to the 1600's in Pendleton County,
> VA (now WV). Some of their homes still are standing. Some of the
> windows even show "ripples" from the flow.
Glass indeed flows but the rate of flow is often exaggerated. The clue
that the flow rate is very very slow is that there are perfectly
servicable optical instruments from the 19th century still around. A
friend of mine has an 18th century telescope that cannot be much worse
than it was when it was made. The images are as good as can be expected
from a telecope built before optical glass was developed. Telescopes are
very sensitive to errors in the shape of the object lens or mirror. An
error of about 0.25 microns is fatal for a refracting astronomical
telescope. 0.063 microns is very bad for a reflecting telescope.
... The times have been,
That, when the brains were out,
the man would die. ... Macbeth
Chuck Simmons email@example.com