On 20 July 1969, a historical milestone took place: Neil Armstrong became the first man to set foot on the Moon. Here, he spoke his now-famous words: "That's one small step for [a] man, one giant leap for mankind." This memorable moment was broadcast live around the world on television and radio. It became the most watched TV programming up to that date, with over 500 million viewers worldwide, and was covered heavily in the press. This event has also help a lasting impression in popular culture, including reference and portrayal in film, television, video games, folklore, literature and more.

This moment was integral and influential for astronomy and space travel research. Not only does this event hold importance for the space industry, but also for humankind. Sending two astronauts into space, landing smoothly on the Moon and returning them safely to Earth was a dream many believed to be impossible. This huge achievement allowed for the conception and development of more human spaceflight missions.

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In July 2019, IAU100 will be celebrating this important milestone.