In the first episode of Buck Rogers, the 1980s television series about an astronaut from the present marooned in the 25th century, our hero visits a museum of the future. A staff member brandishes a mid-20th-century hair dryer. “Early hand laser,” he opines. As an observation of how common knowledge gets lost over time, it’s both funny and poignant. Because our museums also stock items from the past that completely baffle the experts. One of the Strongest Clues: The Map Few are as intriguing as the hundred or so Roman…