When history turns a corner

People power is changing the face of the Middle East, but the democracy deal isn't sealed yet .How can you tell when history turns a corner? An assassination in 1914, a sneak attack in 1941, a wall falling in 1989--each came with a bang that was impossible to mistake once it happened, even if no one saw it coming.
Across the Middle East last week, a tide of good news suggested that another corner might be near...