Portal:History of science/Selected anniversaries/January 9
- 1757 - Death of Bernard le Bovier de Fontenelle, French scientist and man of letters (b. 1657)
- 1757 - Death of Louis Bertrand Castel, French mathematician (b. 1688)
- 1799 - Death of Maria Gaetana Agnesi, Italian scientist (b. 1718)
- 1816 - Sir Humphry Davy tests the Davy lamp for miners at Hebburn Colliery
- 1839 - The French Academy of Sciences announces the Daguerreotype photography process
- 1848 - Death of Caroline Herschel, German-born astronomer (b. 1750)
- 1864 - Birth of Vladimir Steklov, Russian mathematician (d. 1926)
- 1868 - Birth of S. P. L. Sørensen, Danish chemist (d. 1939)
- 1894 - New England Telephone and Telegraph installs the first battery-operated telephone switchboard in Lexington, Massachusetts
- 1918 - Death of Émile Reynaud, French scientist (b. 1844)
- 1922 - Death of Har Gobind Khorana, Nobel laureate
- 1923 - Juan de la Cierva makes the first autogyro flight
- 1975 - Death of Pyotr Novikov, Russian mathematician (b. 1901)
- 1998 - Death of Kenichi Fukui, Japanese chemist, Nobel Prize in Chemistry laureate (b. 1918)