Re: ATM Hogging Out

[lifedata@vol.com]

>Everyone knows (especially Bob May) that gravity causes the disk on the
>bottom to become convex while the one on top becomes concave.

It seems to be great wisdom to say that gravity doesn't cause the
concavity.  That's only partially true.

The laws of physics show that gravity is PARTLY the cause.  Pressure? 
Certainly.  But will anyone swear that gravity will _not_ cause any
pressure at the interface?

It is obvious that gravity is partially responsible in cases in which an
ATMer is advices _not_ to put any pressure on the mirror or tool with
their hands.  Gravity is enough in that case.

Some have said you could grind a mirror on the ceiling.  I'd say that is
true with a small mirror.  But try it with a 20 inch mirror!  The
pressure that gravity causes is reversed and transferred to your hands
or your super-beefed-up grinding machine.

That same pressure is applied to the tool/mirror interface when working
it normally.  Therefore it is part of the grinding/concaving force.

It's nothing to fight over, obviously.  But consider an 16 inch mirror
operation.  Gravity does part of it.  Your hands do part of it.  If you
say "gravity doesn't do it," because it contributes only part of it, you
could as easily say "your hands or your machine spindle don't do it,"
because they contribute only part of it.  (Yeah I know, you CAN apply
more pressure with one than the other.  That doesn't mean that gravity
does nothing.)

Jim L