Through remarkable archaeological excavations, Valerie Hansen, author of “The Silk Road: A New History,” pieces together the dynamic and complicated history of the Silk Road. Hansen discusses the impact of micro exchanges along these prolific trade routes, the cultural and historical significance of coins, and what she refers to as the “time capsule of Silk Road history,” the Mogao caves at Dunhuang. Hansen is professor of history at Yale University, where she teaches Chinese and world history.