Smith's?

J: what time are we leaving tomorrow morning?
A: like 8:20.
J: and it takes half an hour to get there?
A: about thirty five minutes.  But I always leave extra time in case the bridge goes up.
J: does it ever go up?
A: only when I'm late, and then it always does.
J: kind of like that one law.  Who was it?
A: Milton's law?
J: No, that's not it.
A: Newton.  No, wait that's a real one.
J: Smith's...
A: Murphy's Law!

We're in college.