New Light on Bruno Rossi’s 1933 Cosmic-Ray Expedition to the Then-Italian Colony of Eritrea

The recent discovery of new documentation concerning Bruno Benedetto Rossi’s life and career provides new information about Italian and European cosmic-ray physics during the 1930s. The present article analyses part of this new material, focusing on documents that allow a thorough reconstruction of Rossi’s scientific expedition to Eritrea, which was a colony of fascist Italy at the time. We examine Rossi’s scientific practices step-by-step and highlight the institutional and political endeavors that allowed the expedition to take place. Discussing the fascist-colonial context of the expedition provides a key tool to understand the facts reported completely. We also consider the interesting yet forgotten scientific collaboration Rossi had on that occasion with Arthur H. Compton.