Read an excerpt from minding the heavens

Mastermind without a Telescope

Jacobus Kapteyn, a plainly dressed, thin man with a long neck and heavy eyelids, sat in animated conversation with his fellow travelers in the second-class compartment of a train. He spoke in the Low Saxon 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.

A salesman ran after him, calling out, “Professor! You forgot your bag of samples!” Kapteyn stopped and acknowledged the man’s help. “Thank you very much! But these are not samples, you know.”

The salesman replied, “Well then, if you wish, your bag of stars!”

The story, one of many fondly recalled by Kapteyn’s friends, illustrates several of the personality traits that made him a much-loved figure among his neighbors and among astronomers all over the world. And the salesman’s joke about the bag of stars is closer to the truth than he realized, for Kapteyn made it his specialty to study the known universe through representative samples of stars from around the celestial sphere. Throughout his career at Groningen, Kapteyn painstakingly added data to his “bag of stars” until, near the end of his life, he could pull out a carefully wrought model of the stellar system, the so-called “Kapteyn Universe.”

(Excerpt from Chapter 7)