Tamar Rogoff, a 54-year-old experimental- theatre artist and choreographer, is famous for turning impossible things into “art.” She did a show in which the actors were six-month-old babies, another in which the actors were both blind and deaf, and yet a third in which a plot unfolded-is this improbable, or what?-through honest-to-God insomniacs trying to get sleep in various nooks and crannies of the theatre. “I love the challenges of creating art in the face of hurdles,” Rogoff says with characteristic understatement. “You’re never on automatic.”