The Silent Treatment: When People Leave You Guessing

Maybe they just didn't hear you. Or maybe they heard you just fine and have decided that you're an idiot, not even worth responding to. Maybe they got your message but are simply too busy to respond. Maybe they're just quietly thinking it over and still haven't decided. Maybe they're so apologetic that they don't know what to say. Maybe they're just having fun leaving you dangling.
 Whatever it is, it has been longer than you expected. The silence is deafening.
What does it mean?

Silence is a window into a fundamental misunderstanding in semiotics, the study of signs. In general and even in academic research, we assume that a sign is a thing. We say, "A green light means go," as though the meaning was in the light itself. But if signs are things, are all things signs? How do we know which things are signs and which things aren't? And what about silence? It's not a thing.
How can the absence of a thing be a sign? And yet it is.