Big Dumb Objects always provide an interesting starting point. The Stone, as the Americans christen the hollowed-out asteroid that appears above 21st-century Earth in Eon, is full of mysteries. It has the exact same profile as Juno, but much less mass, because someone has hollowed it out into seven enormous chambers. Could it be from humanity’s future? Or a possible future? And if so, does it hold the answers to avert a Russian-American nuclear…