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 the Second World War. 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.

中文翻译：

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澳大利亚和国际天文学联合会：1973 年悉尼大会

国际天文学联合会成立于 1919 年，是代表专业天文学家的国际组织。澳大利亚成立后不久就加入了工会，但由于财政困难，退出了几年，直到第二次世界大战前重新加入。任何国家可以对联盟做出的主要非财政贡献是每三年在不同的国家和城市举办一次大会。澳大利亚在 1967 年或 1970 年申办大会失败后，又一次申办了 1973 年。第二次申办被工会执行委员会接受，并在工会秘书长的一封信中得到确认。由于一些外部威胁，大会的五年规划和组织变得困难重重。主要的一个是波兰迟到的提议，将 1973 年的议会搬到华沙以庆祝哥白尼诞辰 500 周年。继澳大利亚的普通大会之后，在波兰举行的特别大会的妥协导致悉尼的海外参与者人数减少。尽管存在这些问题和其他问题，1973 年的大会仍被认为是非常成功的。