Australia and the International Astronomical Union: the 1973 Sydney general assembly

Formed in 1919, the International Astronomical Union is the international body representing professional astronomers. Australia joined the union soon after its formation but, due to financial difficulties, dropped out for a few years until re-joining just before World War 2. The main non-financial contribution any country can make to the union is to host one of its general assemblies that are held in different countries and cities every three years. After Australia's bid to host a general assembly in 1967 or 1970 was unsuccessful, another bid was made for 1973. This second bid was accepted by the union's executive council and confirmed in a letter from the union's general secretary. The five years of planning and organisation for the assembly were made difficult by several external threats. The main one was the late proposal from Poland to move the 1973 assembly to Warsaw to celebrate the 500th anniversary of the birth of Copernicus. A compromise of an extraordinary general assembly in Poland following the ordinary one in Australia led to reduced numbers of overseas participants in Sydney. Despite this and other problems, the 1973 general assembly was regarded as highly successful.