An interesting question hit my inbox this week. How far south can an aurora be seen? Specifically, are the “northern lights” ever visible from Timbuktu? A 2004 New York Times article about medieval Arabic manuscripts triggered the question. The city of Timbuktu, Mali, was one of Africa’s intellectual hubs when the Renaissance was barely a twinkle in Europeans’ eyes. The article focused on efforts to rescue the ancient manuscripts. One 16th-century...