One summer's day a few years ago, my daughter and her friends piled into a car that one of them had recently gotten a license to drive. "Where are you going?" I asked with false calm. "We're driving up Wisconsin Avenue until it turns into Rockville Pike," my daughter said, naming some roads in and around Washington, D.C. "Then," she continued, "we're gonna keep on driving up Rockville Pike. We want to see what's at the end."