text: glass windows and vaccuums? i am learning about pressure in science class and i have a question about pressure on windows.  in normal life, air pressure doesn't collapse a window because it is pushing on it from all sides.  however, i once saw a demonstration at a museum of a very small vaccuum in which a science experiment was performed.  the sides were all made out of glass.  since the inside was a vaccuum, there was no air pressure inside it.  why didn't the air crush the vaccuum canister?  is it possible to simply manafacture glass strong enough to resist that pressure?  a good, scientifically backed answer will be appreciated. strength of glass comes from thickness and distance between supports  the glass may have been thick it may have been poly carbonate it may have been a small window  absolute vacuum is roughly -15 psi. so a letter size window will have about 1000 pounds pushing against it. stong piece of glass. or perhaps it was only a slight vacuum, 1 or 2 psi