With this setback, Rossi began an important phase of his career. He summarised this period in a memoir: "The Decay of 'Mesotrons' (1939–1943): Experimental Particle Physics in the Age of Innocence", which he presented in a symposium at Fermilab in 1980. On 12 October 1938, the Rossis left for Copenhagen, where the Danish physicist, Niels Bohr, had invited him to study. The couple had no intention of returning to Italy, and Bohr facilitated Rossi's search for a more secure position by sponsoring a conference attended by leading physicists. He hoped that one of them would find Rossi a job, and soon, Rossi received an invitation to come to the University of Manchester, where Blackett was developing a major center of cosmic ray research. After a pleasant two months in Denmark, Rossi and Nora arrived in Manchester.