Portal:History of science/Selected anniversaries/April 20
- 1534 - Jacques Cartier begins his voyage, in which he will discover Canada and Labrador
- 1646 - Birth of Charles Plumier, French botanist (d. 1704)
- 1862 - The first pasteurization test completed by Louis Pasteur and Claude Bernard
- 1904 - Birth of George Stibitz, American scientist (d. 1995)
- 1918 - Birth of Kai Siegbahn, Swedish physicist, Nobel Prize laureate (d. 2007)
- 1918 - Death of Karl Ferdinand Braun, German physicist, Nobel Prize laureate (b. 1850)
- 1927 - Birth of Karl Alexander Müller, Swiss physicist, Nobel Prize laureate
- 1928 - Birth of Gerald S. Hawkins, English astronomer (d. 2003)
- 1932 - Death of Giuseppe Peano, Italian mathematician (b. 1858)
- 1963 - Birth of Aubrey de Grey, British biomedical gerontologist
- 2003 - Death of Bernard Katz, German-born biophysicist, recipient of the Nobel Prize in Physiology or Medicine (b. 1911)