Portal:History of science/Selected anniversaries/April 13
- 1802 - Birth of Leopold Fitzinger, Austrian zoologist (d. 1884)
- 1850 - Birth of Arthur Matthew Weld Downing, British astronomer (d. 1917)
- 1853 - Death of Leopold Gmelin, German chemist (b. 1788)
- 1855 - Death of Henry De la Beche, English geologist (b. 1796)
- 1880 - Death of Robert Fortune, Scottish botanist (b. 1813)
- 1909 - Birth of Stanisław Marcin Ulam, Polish mathematician (d. 1984)
- 1941 - Birth of Michael Stuart Brown, American geneticist, Nobel laureate
- 1941 - Death of Annie Jump Cannon, American astronomer (b. 1863)
- 1953 - CIA director Allen Dulles launches the mind-control program MKULTRA
- 1974 - Western Union (in cooperation with NASA and Hughes Aircraft) launches the U.S.'s first commercial geosynchronous communications satellite, Westar 1
- 1983 - Death of Theodore Stephanides, Greek doctor and naturalist (b. 1896)
- 2008 - Death of John Wheeler, American physicist and educator (b. 1911)