Riding my bike up Union Street in Park Slope on a late summer evening: people sit out on stoops enjoying barbecues in small, neighborly clusters. Kids play ball on the sidewalk, the sounds of hiphop music blare from speakers perched on stairs or in open car doors. Then, in the midst of this warm, friendly chaos, a ghostly, silent spectacle: a group of twenty-somethings is moving up the street wearing illuminated earphones and dancing along snake-like in a kind of sinuous, self-contained queue. I realize I have read about something like this before: a ‘flash mob’-styled dance party in which all of the participants don headphones and dance to music only they can here. Alone, together… The contrast between this in-the-know, hipster spectacle and the old-style Brooklyn neighborhood, where it wouldn’t be out of character to see a group of carolers at Christmas, or perhaps a community barbecue, seems both laughable and sad.