1478: Pazzi conspirators attack Lorenzo de’ Medici and kill Giuliano de’ Medici in Florence

1920: Harlow Shapley and Heber D. Curtis hold the “Great Debate” on the nature of nebulae, galaxies, and the size of the universe at the US National Academy of Sciences, Washington, D.C.

1945: Marshal Philippe Pétain, leader of France’s Vichy collaborationist regime during World War II, is arrested for treason

1956: First modern container ship, the Ideal X, leaves Port Newark, New Jersey for Houston, Texas

1986: The world’s worst nuclear disaster occurs when the fourth reactor at the Chernobyl nuclear power station in the Soviet Union explodes, resulting in 31 deaths and radioactive contamination spreading to much of Western Europe

2005: Under international pressure, Syria withdraws the last of its 14,000 troops from Lebanon, ending its 29-year military domination of the country

Source: Onthisday.com