Working on topology homework.  Trying to decide what sets are open under the parameters we were given.  The professor was talking about this in class last week.  And while we were all massively confused and trying to decide if they were open, he walks over and starts swinging the door open and closed, open and closed, and I am thinking, what in the world????  And he says "I am not airing out the room because I farted, I am trying to give you a hint."  The class just busts out laughing.  Apparently, a set is not like a door.  A door is either open or closed.  In topology land sets can be neither open nor closed, both open and closed, and who knows what else.  So he was trying to tell us that a set in topology is NOT like a door.  So silly!

Though this does remind me of a song from grade school music class.  the words go something like "when is a door not a door", which repeats a bunch of times until you get to the punchline, which is "when it is ajar".  A Jar.  Ha!