io9 is proud to present fiction from Lightspeed Magazine . Once a month, we feature a story from Lightspeed’s current issue . This month’s selection is “Sarah’s Laugh” by Melissa A Watkins. Enjoy! Sarah’s Laugh by Melissa A Watkins Everyone knows the Walls around the cities fell. What some people don’t remember is that the first one fell because of a laugh. It sounded like a ringing bell. Not like it came out of a baby at all. That was the first thing I told the scholar boy. He was a grown man, a researcher. He looked it, too. Big round glasses, chubby cheeks, curly hair. He asked about the laugh while walking through the wet market in the parking lot of one of the old Chinatown groceries. It was early, and if you squinted downhill, you could see the shapes of gulls dipping down past the peaks of the Golden Gate Bridge, weaving in and out of the cables like kids playing cat’s cradle.…