"It's invisible," says Rob Murphy. "And sometimes it moves. Sometimes it's an oval; sometimes an oblong with no corners." On one level, then, there's nothing there at all. Yet those, for many years, were the parameters of his working life. As a relief pitcher for eight MLB teams between 1985 and 1995, all his focus was on that void behind the batter, and the elusive margins between strike and ball. Little wonder, then, if another great passion of Murphy's life is all about giving definition to something most of us...