As America has turned away from searching for extraterrestrial intelligence, China has built the world’s largest radio dish for precisely that purpose. Last January, the Chinese Academy of Sciences invited Liu Cixin, China’s preeminent science-fiction writer, to visit its new state-of-the-art radio dish in the country’s southwest. Almost twice as wide as the dish at America’s Arecibo Observatory, in the Puerto Rican jungle, the new Chinese dish is the largest in the world, if not the universe. Though it is sensitive enough to detect spy satellites even when they’re not broadcasting, its main uses will be scientific, including an unusual...