The egg, you see, is a very sexy thing. Egg is like birth. Eggshell is sexy. Egg yolk is definitely sexy. Oh, I love egg.
For Hamlet, greatness means willingness to fight for reasons as thin as an eggshell: anyone would fight for things that matter; true heroes take their personal honor so seriously they will fight for things that don’t matter.
The atmosphere almost looks like an eggshell on an egg, it's so thin. We know that we don't have much air - we need to protect what we have.