These types of random Metro conversations are fascinating to watch. I guess it's because no one can accuse you of eavesdropping when you're caught in the midst of one -- you can't help hearing; it's completely quiet on the train otherwise. And because they're based on small-talk, so it's bare-bones conversation that anyone can understand. There's no inside jokes, no names of friends mentioned. You can listen as they talk more quickly and excitedly when they have something in common (We've both been to horse races in Kentucky!) and quietly awkward when topics run out. And you can also watch how people on the margins get sucked in. The man sitting across from me, wearing a black sport coat and light blue bow tie for some unknown reason, was also an accidental spectator of the burgeoning camraderie between the retirees. He watched it over the top of his newspaper, a small smile on his face.

The Metro seems to be D.C.'s most obvious melting pot. And the combination of people in any given area seem to form something akin to a chemical reaction.... a social reaction. Every car contains a certain amount of Potential Conversation (PC), according to how chatty and relaxed people are. Get four or five chatty strangers together and you've got a high level of PC. The catalyst? Just ask what time it is.

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