Pius XI

Subject of the Kingdom of Lombardy–Venetia, later becoming an Italian citizen. Signed the Lateran Treaty with Italy (1929), establishing Vatican City as a sovereign state. Inaugurated the Vatican Radio (1931). Refounded the Pontifical Academy of Sciences (1936).

Instituted the feast of Christ the King. Opposed Nazism and Communism. During his pontificate, Catholic priest and physicist Georges Lemaître proposed what he called the "hypothesis of the primeval atom", now regarded as the first formulation of the Big Bang theory of the origin of the universe.