On Sun, 13 Jul 2003 19:34:22 GMT, bonomi@c-ns. (Robert Bonomi) wrote:

In article ,
Jeff Cochran wrote:
BZZZZZT yourself, there is no way to panels of glass (even small ones)
could support the pressure of even the smallest vacuum.

Medium size home aquariums have glass panels supporting pressure differentials
of several PSI.

Commercial aquariums -- e.g. the Chicago Aquarium have glass panels handling
pressure differentials in excess of 10PSI.

Two issues. One is that the glass in commercial aquariums is quite
thick, thicker than would be practical, or cost effective, in building
a window. Second is that glass in an aquarium is a far cry from glass
resisting a vacuum. In an aquarium, there is pressure on both sides,
and the glass has to withstand the differential. In a vacuum, there's
no pressure on one side.

Just _what_ is the difference between 30 PSI on one side, and 15 PSI on
the other, vs 15 PSI on one side, and 0 PSI on the other?

Obviously never been in a lab and created a vacuum with a flat
panel...

Pressure differential isn't simple x-y math. And the closer you get
to a true vacuum the less predictable the differential forces actually
are. To withstand pressure differential, and 15 PSI is actually quite
a strong differential for a flat glass panel of window pane thickness,
requires a structural design which can distribute the force throughout
the material. Hence the fact that most vacuum containers are rounded
or globes.

But this isn't a physics forum, and I'll never convince you here.

Jeff