Portal:History of science/Selected anniversaries/December 21
- 1805 - Birth of Thomas Graham, British chemist (d. 1869)
- 1824 - Death of James Parkinson, English physician, geologist, paleontologist, and political activist (b. 1755)
- 1878 - Birth of Jan Łukasiewicz, Polish philosopher and mathematician (d. 1956)
- 1889 - Birth of Sewall Wright, American biologist (d. 1988)
- 1889 - Friedrich August von Quenstedt, German geologist (b. 1809)
- 1890 - Birth of Hermann Joseph Muller, American geneticist and Nobel laureate (d. 1967)
- 1968 - Apollo program: Apollo 8, the first manned mission to the moon, is launched from the Kennedy Space Center in Florida. At 2h:50m:37s Mission elapsed time (MES), the crew performs the first ever manned Trans Lunar Injection and become the first humans to leave Earth's gravity
- 2004 - Death of Autar Singh Paintal, Indian medical scientist (b. 1925)