Jacobus Kapteyn, a plainly dressed, thin man with a long neck and heavy eyelids, sat in animated conversation with his fellow travelers in the third-class compartment of a train. He spoke in the dialect of Groningen, a small provincial capital in the Netherlands, although he came from Barneveld, farther to the south. His seatmates, who were mostly traveling salesmen, had all but forgotten that he was not one of them but a highly educated professor of astronomy, a teacher and a researcher who, like other university professors, had been appointed to his post by the Crown. University faculty members were rarely seen outside of the first class compartments.

The train clanked and screeched to a halt at Groningen, and Kapteyn hastily concluded his conversation. He threaded his way among the salesmen’s large black bags and jumped off the train, quite forgetting his own luggage. This was not unusual; he routinely misplaced his wallet and forgot appointments, and his wife categorically refused to buy any more umbrellas because he promptly lost them.