Portal:History of science/Selected anniversaries/April 21

April 21:

 * 1557 - Death of Petrus Apianus, German mathematician (b. 1495)
 * 1652 - Birth of Michel Rolle, French mathematician (d. 1719)
 * 1719 - Death of Philippe de La Hire, French mathematician and historian (b. 1640)
 * 1774 - Birth of Jean-Baptiste Biot, French physicist (d. 1862)
 * 1825 - Death of Johann Friedrich Pfaff, German mathemattician (b. 1765)
 * 1851 - Birth of Charles Barrois, French geologist (d. 1939)
 * 1882 - Birth of Percy Williams Bridgman, American physicist, Nobel laureate (d. 1961)
 * 1889 - Birth of Paul Karrer, Swiss chemist, Nobel laureate (d. 1971)
 * 1915 - Birth of Garrett Hardin, American ecologist (d. 2003)
 * 1951 - Birth of Michael Hartley Freedman, American mathematician
 * 1965 - Death of Edward Victor Appleton, English physicist, Nobel Prize laureate (b. 1892)
 * 1980 - Death of Alexander Oparin, Russian biochemist (b. 1894)
 * 1994 - The first discoveries of extrasolar planets are announced by astronomer Aleksander Wolszczan