As are some boats flat bottomed, but they have sloped sides to compensate for this. Anyway, enough bickering about physics. I do that all day long.

BTW, you are correct sir, with the Germans starting to pull the crap they were pulling (invading the rest of Europe and such), we told them no more Helium. Since Helium was not readily available to them, they picked the next best thing, Hydrogen. It just so happens that Hydrogen will react very violently. Ask our astronauts, its one of the fuels they ride into space on.