The following year, Bok broke off his thesis studies at Groningen with Piet van Rhijn and moved across the Atlantic to Cambridge, Massachusetts, on the invitation of Harlow Shapley, Director of Harvard College Observatory, whom he had also met at the same IAU Assembly where he met Priscilla. On September 9, 1929, two days after moving to the US, the two were married. This caused some awkwardness with their mutual superior Shapley, who regarded Priscilla as something of a protégée and was protective of her. While Bok had the greatest admiration for Shapley, it took Shapley time to build the required level of trust with Bok.