INQUIRER: You’ve seen them, even if you don’t remember it. You’re crossing the street and something catches your eye, a flash of color amid the rush of feet. You wait for the light to change and the traffic to thin, and there it is: a rectangular shape embedded in the asphalt, with a message etched in silhouette: TOYNBEE IDEA   IN KUBRICK’S 2001   RESURRECT DEAD   ON PLANET JUPITER Philadelphia is not the only city where the cryptic messages have appeared. They’ve turned up in New York, Boston, and Kansas City, Mo., and as far afield as Buenos Aires. […]