Timothy O'Connor wrote:

This is a really stupid question (that someone asked me the other day, and
I
didnt have any reasonable answer), but why is it not possible to simply
mold
a mirror to shape, rather than grind it? I would have thought that it
would
be possible get it done with a great deal of acuracy these days.
(obviously
not, but Im not sure why)

Well... may not you or I, but it has been tried with varying degrees of
success. Most notably, the Goddard Space Center team has used the carbon
replication technique to make multiple copies of ultra-lightweight
high-accuracy mirrors. Dr Peter Chen gave a great presentation on this at
the 2001 Stellafane convention:

http://www.astro-nut.com/stchen.html

Cheers,

Paul

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